Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

115 files changed, 16293 insertions, 0 deletions

diff --git a/testing/web-platform/tests/resources/test-only-api.js b/testing/web-platform/tests/resources/test-only-api.js
new file mode 100644
index 0000000000..a66eb44ede
--- /dev/null
+++ b/testing/web-platform/tests/resources/test-only-api.js
@@ -0,0 +1,31 @@
+'use strict';
+
+/* Whether the browser is Chromium-based with MojoJS enabled */
+const isChromiumBased = 'MojoInterfaceInterceptor' in self;
+/* Whether the browser is WebKit-based with internal test-only API enabled */
+const isWebKitBased = !isChromiumBased && 'internals' in self;
+
+/**
+ * Loads a script in a window or worker.
+ *
+ * @param {string} path - A script path
+ * @returns {Promise}
+ */
+function loadScript(path) {
+  if (typeof document === 'undefined') {
+    // Workers (importScripts is synchronous and may throw.)
+    importScripts(path);
+    return Promise.resolve();
+  } else {
+    // Window
+    const script = document.createElement('script');
+    script.src = path;
+    script.async = false;
+    const p = new Promise((resolve, reject) => {
+      script.onload = () => { resolve(); };
+      script.onerror = e => { reject(`Error loading ${path}`); };
+    })
+    document.head.appendChild(script);
+    return p;
+  }
+}
diff --git a/testing/web-platform/tests/resources/test-only-api.js.headers b/testing/web-platform/tests/resources/test-only-api.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/test-only-api.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600
diff --git a/testing/web-platform/tests/resources/test-only-api.m.js b/testing/web-platform/tests/resources/test-only-api.m.js
new file mode 100644
index 0000000000..984f635aba
--- /dev/null
+++ b/testing/web-platform/tests/resources/test-only-api.m.js
@@ -0,0 +1,5 @@
+/* Whether the browser is Chromium-based with MojoJS enabled */
+export const isChromiumBased = 'MojoInterfaceInterceptor' in self;
+
+/* Whether the browser is WebKit-based with internal test-only API enabled */
+export const isWebKitBased = !isChromiumBased && 'internals' in self;
diff --git a/testing/web-platform/tests/resources/test-only-api.m.js.headers b/testing/web-platform/tests/resources/test-only-api.m.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/test-only-api.m.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600
diff --git a/testing/web-platform/tests/resources/test/README.md b/testing/web-platform/tests/resources/test/README.md
new file mode 100644
index 0000000000..edc03ef214
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/README.md
@@ -0,0 +1,83 @@
+# `testharness.js` test suite
+
+The test suite for the `testharness.js` testing framework.
+
+## Executing Tests
+
+Install the following dependencies:
+
+- [Python 2.7.9+](https://www.python.org/)
+- [the tox Python package](https://tox.readthedocs.io/en/latest/)
+- [the Mozilla Firefox web browser](https://mozilla.org/firefox)
+- [the GeckoDriver server](https://github.com/mozilla/geckodriver)
+
+Make sure `geckodriver` can be found in your `PATH`.
+
+Currently, the tests should be run with the latest *Firefox Nightly*. In order to
+specify the path to Firefox Nightly, use the following command-line option:
+
+    tox -- --binary=/path/to/FirefoxNightly
+
+### Automated Script
+
+Alternatively, you may run `tools/ci/ci_resources_unittest.sh`, which only depends on
+Python 2. The script will install other dependencies automatically and start `tox` with
+the correct arguments.
+
+## Authoring Tests
+
+Test cases are expressed as `.html` files located within the `tests/unit/` and
+`tests/functional/` sub-directories. Each test should include the
+`testharness.js` library with the following markup:
+
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+
+This should be followed by one or more `<script>` tags that interface with the
+`testharness.js` API in some way. For example:
+
+    <script>
+    test(function() {
+        1 = 1;
+      }, 'This test is expected to fail.');
+    </script>
+
+### Unit tests
+
+The "unit test" type allows for concisely testing the expected behavior of
+assertion methods. These tests may define any number of sub-tests; the
+acceptance criteria is simply that all tests executed pass.
+
+### Functional tests
+
+Thoroughly testing the behavior of the harness itself requires ensuring a
+number of considerations which cannot be verified with the "unit testing"
+strategy. These include:
+
+- Ensuring that some tests are not run
+- Ensuring conditions that cause test failures
+- Ensuring conditions that cause harness errors
+
+Functional tests allow for these details to be verified. Every functional test
+must include a summary of the expected results as a JSON string within a
+`<script>` tag with an `id` of `"expected"`, e.g.:
+
+    <script type="text/json" id="expected">
+    {
+      "summarized_status": {
+        "message": null,
+        "stack": null,
+        "status_string": "OK"
+      },
+      "summarized_tests": [
+        {
+          "message": "ReferenceError: invalid assignment left-hand side",
+          "name": "Sample HTML5 API Tests",
+          "properties": {},
+          "stack": "(implementation-defined)",
+          "status_string": "FAIL"
+        }
+      ],
+      "type": "complete"
+    }
+    </script>
diff --git a/testing/web-platform/tests/resources/test/conftest.py b/testing/web-platform/tests/resources/test/conftest.py
new file mode 100644
index 0000000000..7253cac9ac
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/conftest.py
@@ -0,0 +1,269 @@
+import copy
+import json
+import os
+import ssl
+import sys
+import subprocess
+import urllib
+
+import html5lib
+import py
+import pytest
+
+from wptserver import WPTServer
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+WPT_ROOT = os.path.normpath(os.path.join(HERE, '..', '..'))
+HARNESS = os.path.join(HERE, 'harness.html')
+TEST_TYPES = ('functional', 'unit')
+
+sys.path.insert(0, os.path.normpath(os.path.join(WPT_ROOT, "tools")))
+import localpaths
+
+sys.path.insert(0, os.path.normpath(os.path.join(WPT_ROOT, "tools", "webdriver")))
+import webdriver
+
+
+def pytest_addoption(parser):
+    parser.addoption("--binary", action="store", default=None, help="path to browser binary")
+    parser.addoption("--headless", action="store_true", default=False, help="run browser in headless mode")
+
+
+def pytest_collect_file(file_path, path, parent):
+    if file_path.suffix.lower() != '.html':
+        return
+
+    # Tests are organized in directories by type
+    test_type = os.path.relpath(str(file_path), HERE)
+    if os.path.sep not in test_type or ".." in test_type:
+        # HTML files in this directory are not tests
+        return
+    test_type = test_type.split(os.path.sep)[1]
+
+    # Handle the deprecation of Node construction in pytest6
+    # https://docs.pytest.org/en/stable/deprecations.html#node-construction-changed-to-node-from-parent
+    if hasattr(HTMLItem, "from_parent"):
+        return HTMLItem.from_parent(parent, filename=str(file_path), test_type=test_type)
+    return HTMLItem(parent, str(file_path), test_type)
+
+
+def pytest_configure(config):
+    config.proc = subprocess.Popen(["geckodriver"])
+    config.add_cleanup(config.proc.kill)
+
+    capabilities = {"alwaysMatch": {"acceptInsecureCerts": True, "moz:firefoxOptions": {}}}
+    if config.getoption("--binary"):
+        capabilities["alwaysMatch"]["moz:firefoxOptions"]["binary"] = config.getoption("--binary")
+    if config.getoption("--headless"):
+        capabilities["alwaysMatch"]["moz:firefoxOptions"]["args"] = ["--headless"]
+
+    config.driver = webdriver.Session("localhost", 4444,
+                                      capabilities=capabilities)
+    config.add_cleanup(config.driver.end)
+
+    # Although the name of the `_create_unverified_context` method suggests
+    # that it is not intended for external consumption, the standard library's
+    # documentation explicitly endorses its use:
+    #
+    # > To revert to the previous, unverified, behavior
+    # > ssl._create_unverified_context() can be passed to the context
+    # > parameter.
+    #
+    # https://docs.python.org/2/library/httplib.html#httplib.HTTPSConnection
+    config.ssl_context = ssl._create_unverified_context()
+
+    config.server = WPTServer(WPT_ROOT)
+    config.server.start(config.ssl_context)
+    config.add_cleanup(config.server.stop)
+
+
+def resolve_uri(context, uri):
+    if uri.startswith('/'):
+        base = WPT_ROOT
+        path = uri[1:]
+    else:
+        base = os.path.dirname(context)
+        path = uri
+
+    return os.path.exists(os.path.join(base, path))
+
+
+def _summarize(actual):
+    def _scrub_stack(test_obj):
+        copy = dict(test_obj)
+        del copy['stack']
+        return copy
+
+    def _expand_status(status_obj):
+        for key, value in [item for item in status_obj.items()]:
+            # In "status" and "test" objects, the "status" value enum
+            # definitions are interspersed with properties for unrelated
+            # metadata. The following condition is a best-effort attempt to
+            # ignore non-enum properties.
+            if key != key.upper() or not isinstance(value, int):
+                continue
+
+            del status_obj[key]
+
+            if status_obj['status'] == value:
+                status_obj[u'status_string'] = key
+
+        del status_obj['status']
+
+        return status_obj
+
+    def _summarize_test(test_obj):
+        del test_obj['index']
+
+        assert 'phase' in test_obj
+        assert 'phases' in test_obj
+        assert 'COMPLETE' in test_obj['phases']
+        assert test_obj['phase'] == test_obj['phases']['COMPLETE']
+        del test_obj['phases']
+        del test_obj['phase']
+
+        return _expand_status(_scrub_stack(test_obj))
+
+    def _summarize_status(status_obj):
+        return _expand_status(_scrub_stack(status_obj))
+
+
+    summarized = {}
+
+    summarized[u'summarized_status'] = _summarize_status(actual['status'])
+    summarized[u'summarized_tests'] = [
+        _summarize_test(test) for test in actual['tests']]
+    summarized[u'summarized_tests'].sort(key=lambda test_obj: test_obj.get('name'))
+    summarized[u'summarized_asserts'] = [
+        {"assert_name": assert_item["assert_name"],
+        "test": assert_item["test"]["name"] if assert_item["test"] else None,
+        "args": assert_item["args"],
+        "status": assert_item["status"]} for assert_item in actual["asserts"]]
+    summarized[u'type'] = actual['type']
+
+    return summarized
+
+
+class HTMLItem(pytest.Item, pytest.Collector):
+    def __init__(self, parent, filename, test_type):
+        self.url = parent.session.config.server.url(filename)
+        self.type = test_type
+        # Some tests are reliant on the WPT servers substitution functionality,
+        # so tests must be retrieved from the server rather than read from the
+        # file system directly.
+        handle = urllib.request.urlopen(self.url,
+                                        context=parent.session.config.ssl_context)
+        try:
+            markup = handle.read()
+        finally:
+            handle.close()
+
+        if test_type not in TEST_TYPES:
+            raise ValueError('Unrecognized test type: "%s"' % test_type)
+
+        parsed = html5lib.parse(markup, namespaceHTMLElements=False)
+        name = None
+        self.expected = None
+
+        for element in parsed.iter():
+            if not name and element.tag == 'title':
+                name = element.text
+                continue
+            if element.tag == 'script':
+                if element.attrib.get('id') == 'expected':
+                    try:
+                        self.expected = json.loads(element.text)
+                    except ValueError:
+                        print("Failed parsing JSON in %s" % filename)
+                        raise
+
+        if not name:
+            raise ValueError('No name found in %s add a <title> element' % filename)
+        elif self.type == 'functional':
+            if not self.expected:
+                raise ValueError('Functional tests must specify expected report data')
+        elif self.type == 'unit' and self.expected:
+            raise ValueError('Unit tests must not specify expected report data')
+
+        # Ensure that distinct items have distinct fspath attributes.
+        # This is necessary because pytest has an internal cache keyed on it,
+        # and only the first test with any given fspath will be run.
+        #
+        # This cannot use super(HTMLItem, self).__init__(..) because only the
+        # Collector constructor takes the fspath argument.
+        pytest.Item.__init__(self, name, parent)
+        pytest.Collector.__init__(self, name, parent, fspath=py.path.local(filename))
+
+
+    def reportinfo(self):
+        return self.fspath, None, self.url
+
+    def repr_failure(self, excinfo):
+        return pytest.Collector.repr_failure(self, excinfo)
+
+    def runtest(self):
+        if self.type == 'unit':
+            self._run_unit_test()
+        elif self.type == 'functional':
+            self._run_functional_test()
+        else:
+            raise NotImplementedError
+
+    def _run_unit_test(self):
+        driver = self.session.config.driver
+        server = self.session.config.server
+
+        driver.url = server.url(HARNESS)
+
+        actual = driver.execute_async_script(
+            'runTest("%s", "foo", arguments[0])' % self.url
+        )
+
+        summarized = _summarize(copy.deepcopy(actual))
+
+        print(json.dumps(summarized, indent=2))
+
+        assert summarized[u'summarized_status'][u'status_string'] == u'OK', summarized[u'summarized_status'][u'message']
+        for test in summarized[u'summarized_tests']:
+            msg = "%s\n%s" % (test[u'name'], test[u'message'])
+            assert test[u'status_string'] == u'PASS', msg
+
+    def _run_functional_test(self):
+        driver = self.session.config.driver
+        server = self.session.config.server
+
+        driver.url = server.url(HARNESS)
+
+        test_url = self.url
+        actual = driver.execute_async_script('runTest("%s", "foo", arguments[0])' % test_url)
+
+        print(json.dumps(actual, indent=2))
+
+        summarized = _summarize(copy.deepcopy(actual))
+
+        print(json.dumps(summarized, indent=2))
+
+        # Test object ordering is not guaranteed. This weak assertion verifies
+        # that the indices are unique and sequential
+        indices = [test_obj.get('index') for test_obj in actual['tests']]
+        self._assert_sequence(indices)
+
+        self.expected[u'summarized_tests'].sort(key=lambda test_obj: test_obj.get('name'))
+
+        # Make asserts opt-in for now
+        if "summarized_asserts" not in self.expected:
+            del summarized["summarized_asserts"]
+        else:
+            # We can't be sure of the order of asserts even within the same test
+            # although we could also check for the failing assert being the final
+            # one
+            for obj in [summarized, self.expected]:
+                obj["summarized_asserts"].sort(
+                    key=lambda x: (x["test"] or "", x["status"], x["assert_name"], tuple(x["args"])))
+
+        assert summarized == self.expected
+
+    @staticmethod
+    def _assert_sequence(nums):
+        if nums and len(nums) > 0:
+            assert nums == list(range(1, nums[-1] + 1))
diff --git a/testing/web-platform/tests/resources/test/harness.html b/testing/web-platform/tests/resources/test/harness.html
new file mode 100644
index 0000000000..5ee0f285e8
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/harness.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+  </head>
+  <body>
+    <script>
+function runTest(url, id, done) {
+  var child;
+
+  function onMessage(event) {
+    if (!event.data || event.data.type !== 'complete') {
+      return;
+    }
+
+    window.removeEventListener('message', onMessage);
+    child.close();
+    done(event.data);
+  }
+  window.addEventListener('message', onMessage);
+
+  window.child = child = window.open(url, id);
+}
+    </script>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/idl-helper.js b/testing/web-platform/tests/resources/test/idl-helper.js
new file mode 100644
index 0000000000..2b73527ff2
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/idl-helper.js
@@ -0,0 +1,24 @@
+"use strict";
+
+var typedefFrom = interfaceFrom;
+var dictionaryFrom = interfaceFrom;
+function interfaceFrom(i) {
+    var idl = new IdlArray();
+    idl.add_idls(i);
+    for (var prop in idl.members) {
+        return idl.members[prop];
+    }
+}
+
+function memberFrom(m) {
+    var idl = new IdlArray();
+    idl.add_idls('interface A { ' + m + '; };');
+    return idl.members["A"].members[0];
+}
+
+function typeFrom(type) {
+    var ast = WebIDL2.parse('interface Foo { ' + type + ' a(); };');
+    ast = ast[0]; // get the first fragment
+    ast = ast.members[0]; // get the first member
+    return ast.idlType; // get the type of the first field
+}
diff --git a/testing/web-platform/tests/resources/test/nested-testharness.js b/testing/web-platform/tests/resources/test/nested-testharness.js
new file mode 100644
index 0000000000..d97c1568c7
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/nested-testharness.js
@@ -0,0 +1,80 @@
+'use strict';
+
+/**
+ * Execute testharness.js and one or more scripts in an iframe. Report the
+ * results of the execution.
+ *
+ * @param {...function|...string} bodies - a function body. If specified as a
+ *                                         function object, it will be
+ *                                         serialized to a string using the
+ *                                         built-in
+ *                                         `Function.prototype.toString` prior
+ *                                         to inclusion in the generated
+ *                                         iframe.
+ *
+ * @returns {Promise} eventual value describing the result of the test
+ *                    execution; the summary object has two properties:
+ *                    `harness` (a string describing the harness status) and
+ *                    `tests` (an object whose "own" property names are the
+ *                    titles of the defined sub-tests and whose associated
+ *                    values are the subtest statuses).
+ */
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: getEnumProp(status, status.status),
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
diff --git a/testing/web-platform/tests/resources/test/requirements.txt b/testing/web-platform/tests/resources/test/requirements.txt
new file mode 100644
index 0000000000..95d87c3875
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/requirements.txt
@@ -0,0 +1 @@
+html5lib==1.1
diff --git a/testing/web-platform/tests/resources/test/tests/functional/abortsignal.html b/testing/web-platform/tests/resources/test/tests/functional/abortsignal.html
new file mode 100644
index 0000000000..e6080e96ec
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/abortsignal.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<title>Test#get_signal</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  "use strict";
+
+  setup(() => {
+    assert_implements_optional(window.AbortController, "No AbortController");
+  });
+
+  let signal;
+  let observed = false;
+
+  test(t => {
+    signal = t.get_signal();
+    assert_true(signal instanceof AbortSignal, "Returns an abort signal");
+    assert_false(signal.aborted, "Signal should not be aborted before test end");
+    signal.onabort = () => observed = true;
+  }, "t.signal existence");
+
+  test(t => {
+    assert_true(signal.aborted, "Signal should be aborted after test end");
+    assert_true(observed, "onabort should have been called");
+  }, "t.signal.aborted");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "message": null,
+      "name": "t.signal existence",
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "name": "t.signal.aborted",
+      "properties": {},
+      "status_string": "PASS"
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup.html
new file mode 100644
index 0000000000..468319fdbe
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup.html
@@ -0,0 +1,91 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+"use strict";
+
+var log_sync;
+test(function(t) {
+  log_sync = "";
+  t.add_cleanup(function() { log_sync += "1"; });
+  t.add_cleanup(function() { log_sync += "2"; });
+  t.add_cleanup(function() { log_sync += "3"; });
+  t.add_cleanup(function() { log_sync += "4"; });
+  t.add_cleanup(function() { log_sync += "5"; });
+  log_sync += "0";
+}, "probe synchronous");
+
+test(function() {
+  if (log_sync !== "012345") {
+    throw new Error("Expected: '012345'. Actual: '" + log_sync + "'.");
+  }
+}, "Cleanup methods are invoked exactly once and in the expected sequence.");
+
+var complete, log_async;
+async_test(function(t) {
+  complete = t.step_func(function() {
+    if (log_async !== "012") {
+      throw new Error("Expected: '012'. Actual: '" + log_async + "'.");
+    }
+
+    t.done();
+  });
+}, "Cleanup methods are invoked following the completion of asynchronous tests");
+
+async_test(function(t) {
+  log_async = "";
+  t.add_cleanup(function() { log_async += "1"; });
+
+  setTimeout(t.step_func(function() {
+    t.add_cleanup(function() {
+      log_async += "2";
+      complete();
+    });
+    log_async += "0";
+    t.done();
+  }), 0);
+}, "probe asynchronous");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Cleanup methods are invoked exactly once and in the expected sequence.",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Cleanup methods are invoked following the completion of asynchronous tests",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "probe asynchronous",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "probe synchronous",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async.html
new file mode 100644
index 0000000000..07ade4b93b
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async.html
@@ -0,0 +1,85 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with Promise-returning functions</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+var completeCount = 0;
+var counts = {
+    afterTick: null,
+    afterFirst: null
+};
+
+add_result_callback(function(result_t) {
+  completeCount += 1;
+});
+
+promise_test(function(t) {
+  t.add_cleanup(function() {
+    return new Promise(function(resolve) {
+      setTimeout(function() {
+        counts.afterTick = completeCount;
+        resolve();
+      }, 0);
+    });
+  });
+  t.add_cleanup(function() {
+    return new Promise(function(resolve) {
+
+      setTimeout(function() {
+        counts.afterFirst = completeCount;
+        resolve();
+      }, 0);
+    });
+  });
+
+  return Promise.resolve();
+}, 'promise_test with asynchronous cleanup');
+
+promise_test(function() {
+  assert_equals(
+    counts.afterTick,
+    0,
+    "test is not asynchronously considered 'complete'"
+  );
+  assert_equals(
+    counts.afterFirst,
+    0,
+    "test is not considered 'complete' following fulfillment of first promise"
+  );
+  assert_equals(completeCount, 1);
+
+  return Promise.resolve();
+}, "synchronously-defined promise_test");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "promise_test with asynchronous cleanup",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "synchronously-defined promise_test",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_bad_return.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_bad_return.html
new file mode 100644
index 0000000000..867bde2c39
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_bad_return.html
@@ -0,0 +1,50 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with non-thenable-returning function</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+
+promise_test(function(t) {
+  t.add_cleanup(function() {});
+  t.add_cleanup(function() {
+    return { then: 9 };
+  });
+  t.add_cleanup(function() { return Promise.resolve(); });
+
+  return Promise.resolve();
+}, "promise_test that returns a non-thenable object in one \"cleanup\" callback");
+
+promise_test(function() {}, "The test runner is in an unpredictable state ('NOT RUN')");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'promise_test that returns a non-thenable object in one \"cleanup\" callback' specified 3 'cleanup' functions, and 1 returned a non-thenable value."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "NOTRUN",
+      "name": "The test runner is in an unpredictable state ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "promise_test that returns a non-thenable object in one \"cleanup\" callback",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection.html
new file mode 100644
index 0000000000..e51465e7eb
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection.html
@@ -0,0 +1,94 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with Promise-returning functions (rejection handling)</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+var resolve, reject;
+var completeCount = 0;
+add_result_callback(function(result_t) {
+  completeCount += 1;
+});
+promise_test(function(t) {
+  t.add_cleanup(function() {
+    return new Promise(function(_, _reject) { reject = _reject; });
+  });
+  t.add_cleanup(function() {
+    return new Promise(function(_resolve) { resolve = _resolve; });
+  });
+
+  // The following cleanup function defines empty tests so that the reported
+  // data demonstrates the intended run-time behavior without relying on the
+  // test harness's handling of errors during test cleanup (which is tested
+  // elsewhere).
+  t.add_cleanup(function() {
+    if (completeCount === 0) {
+      promise_test(
+        function() {},
+        "test is not asynchronously considered 'complete' ('NOT RUN')"
+      );
+    }
+
+    reject();
+
+    setTimeout(function() {
+      if (completeCount === 0) {
+        promise_test(
+          function() {},
+          "test is not considered 'complete' following rejection of first " +
+          "promise ('NOT RUN')"
+        );
+      }
+
+      resolve();
+    }, 0);
+  });
+
+  return Promise.resolve();
+}, "promise_test with asynchronous cleanup including rejection");
+
+promise_test(function() {}, "synchronously-defined test ('NOT RUN')");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'promise_test with asynchronous cleanup including rejection' specified 3 'cleanup' functions, and 1 failed."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "promise_test with asynchronous cleanup including rejection",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "synchronously-defined test ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "test is not asynchronously considered 'complete' ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "test is not considered 'complete' following rejection of first promise ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection_after_load.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection_after_load.html
new file mode 100644
index 0000000000..f9b2846100
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection_after_load.html
@@ -0,0 +1,52 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with Promise-returning functions (rejection handling following "load" event)</title>
+</head>
+<body>
+<h1>Promise Tests</h1>
+<p>This test demonstrates the use of <tt>promise_test</tt>. Assumes ECMAScript 6
+Promise support. Some failures are expected.</p>
+<div id="log"></div>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+<script>
+promise_test(function(t) {
+  t.add_cleanup(function() {
+    return Promise.reject(new Error("foo"));
+  });
+
+  return new Promise((resolve) => {
+    document.addEventListener("DOMContentLoaded", function() {
+      setTimeout(resolve, 0)
+    });
+  });
+}, "Test with failing cleanup that completes after DOMContentLoaded event");
+
+promise_test(function(t) {
+  return Promise.resolve();
+}, "Test that should not be run due to invalid harness state ('NOT RUN')");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'Test with failing cleanup that completes after DOMContentLoaded event' specified 1 'cleanup' function, and 1 failed."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "NOTRUN",
+      "name": "Test that should not be run due to invalid harness state ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test with failing cleanup that completes after DOMContentLoaded event",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_timeout.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_timeout.html
new file mode 100644
index 0000000000..429536ce6e
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_timeout.html
@@ -0,0 +1,57 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with Promise-returning functions (timeout handling)</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+"use strict";
+
+promise_test(function(t) {
+  t.add_cleanup(function() {
+    return Promise.resolve();
+  });
+
+  t.add_cleanup(function() {
+    return new Promise(function() {});
+  });
+
+  t.add_cleanup(function() {});
+
+  t.add_cleanup(function() {
+    return new Promise(function() {});
+  });
+
+  return Promise.resolve();
+}, "promise_test with asynchronous cleanup");
+
+promise_test(function() {}, "promise_test following timed out cleanup ('NOT RUN')");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Timeout while running cleanup for test named \"promise_test with asynchronous cleanup\"."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "NOTRUN",
+      "name": "promise_test following timed out cleanup ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "promise_test with asynchronous cleanup",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_bad_return.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_bad_return.html
new file mode 100644
index 0000000000..3cfb28adf2
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_bad_return.html
@@ -0,0 +1,61 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup with value-returning function</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+"use strict";
+
+test(function(t) {
+  t.add_cleanup(function() {});
+  t.add_cleanup(function() { return null; });
+  t.add_cleanup(function() {
+    test(
+      function() {},
+      "The test runner is in an unpredictable state #1 ('NOT RUN')"
+    );
+
+    throw new Error();
+  });
+  t.add_cleanup(function() { return 4; });
+  t.add_cleanup(function() { return { then: function() {} }; });
+  t.add_cleanup(function() {});
+}, "Test that returns a value in three \"cleanup\" functions");
+
+test(function() {}, "The test runner is in an unpredictable state #2 ('NOT RUN')");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'Test that returns a value in three \"cleanup\" functions' specified 6 'cleanup' functions, and 1 failed, and 3 returned a non-undefined value."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Test that returns a value in three \"cleanup\" functions",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "The test runner is in an unpredictable state #1 ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "The test runner is in an unpredictable state #2 ('NOT RUN')",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_count.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_count.html
new file mode 100644
index 0000000000..2c9b51c6d0
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_count.html
@@ -0,0 +1,39 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup reported count</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+promise_test(function(t) {
+    t.add_cleanup(function() {});
+    t.add_cleanup(function() {});
+    t.add_cleanup(function() { throw new Error(); });
+    new EventWatcher(t, document.body, []);
+
+    return Promise.resolve();
+}, 'test with 3 user-defined cleanup functions');
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'test with 3 user-defined cleanup functions' specified 3 'cleanup' functions, and 1 failed."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "test with 3 user-defined cleanup functions",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err.html
new file mode 100644
index 0000000000..60357c66ee
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err.html
@@ -0,0 +1,45 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup: error</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+<script>
+"use strict";
+
+test(function(t) {
+  t.add_cleanup(function() {
+    throw new Error('exception in cleanup function');
+  });
+}, "Exception in cleanup function causes harness failure.");
+
+test(function() {}, "This test should not be run.");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'Exception in cleanup function causes harness failure.' specified 1 'cleanup' function, and 1 failed."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Exception in cleanup function causes harness failure.",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "This test should not be run.",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err_multi.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err_multi.html
new file mode 100644
index 0000000000..80ba1b4959
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err_multi.html
@@ -0,0 +1,52 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup: multiple functions with one in error</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+
+test(function(t) {
+    t.add_cleanup(function() {
+      throw new Error("exception in cleanup function");
+    });
+
+    // The following cleanup function defines a test so that the reported
+    // data demonstrates the intended run-time behavior, i.e. that
+    // `testharness.js` invokes all cleanup functions even when one or more
+    // throw errors.
+    t.add_cleanup(function() {
+      test(function() {}, "Verification test");
+    });
+  }, "Test with multiple cleanup functions");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Test named 'Test with multiple cleanup functions' specified 2 'cleanup' functions, and 1 failed."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Test with multiple cleanup functions",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "Verification test",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_sync_queue.html b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_sync_queue.html
new file mode 100644
index 0000000000..0a61503cc8
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/add_cleanup_sync_queue.html
@@ -0,0 +1,55 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#add_cleanup: queuing tests</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+var firstCleaned = false;
+
+promise_test(function(t) {
+  promise_test(function() {
+    assert_true(
+      firstCleaned, "should not execute until first test is complete"
+    );
+
+    return Promise.resolve();
+  }, "test defined when no tests are queued, but one test is executing");
+
+  t.add_cleanup(function() {
+    firstCleaned = true;
+  });
+
+  return Promise.resolve();
+}, "Test with a 'cleanup' function");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "message": null,
+      "name": "Test with a 'cleanup' function",
+      "status_string": "PASS",
+      "properties": {}
+    },
+    {
+      "message": null,
+      "name": "test defined when no tests are queued, but one test is executing",
+      "status_string": "PASS",
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/api-tests-1.html b/testing/web-platform/tests/resources/test/tests/functional/api-tests-1.html
new file mode 100644
index 0000000000..9de875b0f1
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/api-tests-1.html
@@ -0,0 +1,991 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Sample HTML5 API Tests</title>
+<meta name="timeout" content="6000">
+</head>
+<body onload="load_test_attr.done()">
+<h1>Sample HTML5 API Tests</h1>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+    setup_run = false;
+    setup(function() {
+            setup_run = true;
+          });
+    test(function() {assert_true(setup_run)}, "Setup function ran");
+
+    // Two examples for testing events from handler and attributes
+    var load_test_event = async_test("window onload event fires when set from the handler");
+
+    function windowLoad()
+    {
+        load_test_event.done();
+    }
+    on_event(window, "load", windowLoad);
+
+    test(function() {
+        var sequence = [];
+        var outer = document.createElement("div");
+        var inner = document.createElement("div");
+        outer.appendChild(inner);
+        document.body.appendChild(outer);
+        inner.addEventListener("click", function() {
+            sequence.push("inner");
+        }, false);
+
+        on_event(outer, "click", function() {
+            sequence.push("outer");
+        });
+        inner.click();
+
+        assert_array_equals(sequence, ["inner", "outer"]);
+    }, "on_event does not use event capture");
+
+    // see the body onload below
+    var load_test_attr = async_test("body element fires the onload event set from the attribute");
+</script>
+<script>
+    function bodyElement()
+    {
+        assert_equals(document.body, document.getElementsByTagName("body")[0]);
+    }
+    test(bodyElement, "document.body should be the first body element in the document");
+
+    test(function() {
+        assert_equals(1,1);
+        assert_equals(NaN, NaN, "NaN case");
+        assert_equals(0, 0, "Zero case");
+    }, "assert_equals tests")
+
+    test(function() {
+        assert_equals(-0, 0, "Zero case");
+    }, "assert_equals tests expected to fail")
+
+    test(function() {
+        assert_not_equals({}, {}, "object case");
+        assert_not_equals(-0, 0, "Zero case");
+    }, "assert_not_equals tests")
+
+    function testAssertPass()
+    {
+        assert_true(true);
+    }
+    test(testAssertPass, "assert_true expected to pass");
+
+    function testAssertFalse()
+    {
+        assert_true(false, "false should not be true");
+    }
+    test(testAssertFalse, "assert_true expected to fail");
+
+    function basicAssertArrayEquals()
+    {
+        assert_array_equals([1, NaN], [1, NaN], "[1, NaN] is equal to [1, NaN]");
+    }
+    test(basicAssertArrayEquals, "basic assert_array_equals test");
+
+    function assertArrayEqualsUndefined()
+    {
+        assert_array_equals(undefined, [1], "undefined equals [1]?");
+    }
+    test(assertArrayEqualsUndefined, "assert_array_equals with first param undefined");
+
+    function assertArrayEqualsTrue()
+    {
+        assert_array_equals(true, [1], "true equals [1]?");
+    }
+    test(assertArrayEqualsTrue, "assert_array_equals with first param true");
+
+    function assertArrayEqualsFalse()
+    {
+        assert_array_equals(false, [1], "false equals [1]?");
+    }
+    test(assertArrayEqualsFalse, "assert_array_equals with first param false");
+
+    function assertArrayEqualsNull()
+    {
+        assert_array_equals(null, [1], "null equals [1]?");
+    }
+    test(assertArrayEqualsNull, "assert_array_equals with first param null");
+
+    function assertArrayEqualsNumeric()
+    {
+        assert_array_equals(1, [1], "1 equals [1]?");
+    }
+    test(assertArrayEqualsNumeric, "assert_array_equals with first param 1");
+
+    function basicAssertArrayApproxEquals()
+    {
+        assert_array_approx_equals([10, 11], [11, 10], 1, "[10, 11] is approximately (+/- 1) [11, 10]")
+    }
+    test(basicAssertArrayApproxEquals, "basic assert_array_approx_equals test");
+
+    function basicAssertApproxEquals()
+    {
+        assert_approx_equals(10, 11, 1, "10 is approximately (+/- 1) 11")
+    }
+    test(basicAssertApproxEquals, "basic assert_approx_equals test");
+
+    function basicAssertLessThan()
+    {
+        assert_less_than(10, 11, "10 is less than 11")
+    }
+    test(basicAssertApproxEquals, "basic assert_less_than test");
+
+    function basicAssertGreaterThan()
+    {
+        assert_greater_than(10, 11, "10 is not greater than 11");
+    }
+    test(basicAssertGreaterThan, "assert_greater_than expected to fail");
+
+    function basicAssertGreaterThanEqual()
+    {
+        assert_greater_than_equal(10, 10, "10 is greater than or equal to 10")
+    }
+    test(basicAssertGreaterThanEqual, "basic assert_greater_than_equal test");
+
+    function basicAssertLessThanEqual()
+    {
+        assert_greater_than_equal('10', 10, "'10' is not a number")
+    }
+    test(basicAssertLessThanEqual, "assert_less_than_equal expected to fail");
+
+    function testAssertInherits() {
+        var A = function(){this.a = "a"}
+        A.prototype = {b:"b"}
+        var a = new A();
+        assert_own_property(a, "a");
+        assert_not_own_property(a, "b", "unexpected property found: \"b\"");
+        assert_inherits(a, "b");
+    }
+    test(testAssertInherits, "test for assert[_not]_own_property and insert_inherits")
+
+    test(function()
+    {
+        var a = document.createElement("a")
+        var b = document.createElement("b")
+        assert_throws_dom("NOT_FOUND_ERR", function () {a.removeChild(b)});
+    }, "Test throw DOM exception")
+
+    test(function()
+    {
+        var a = document.createElement("a")
+        var b = document.createElement("b")
+        assert_throws_js(DOMException, function () {a.removeChild(b)});
+    }, "Test throw DOMException as JS exception expected to fail")
+
+    test(function()
+    {
+        assert_throws_js(SyntaxError, function () {document.querySelector("")});
+    }, "Test throw SyntaxError DOMException where JS SyntaxError expected; expected to fail")
+
+    test(function()
+    {
+        assert_throws_js(SyntaxError, function () {JSON.parse("{")});
+    }, "Test throw JS SyntaxError")
+
+    test(function()
+    {
+        assert_throws_dom("SyntaxError", function () {document.querySelector("")});
+    }, "Test throw DOM SyntaxError")
+
+    test(function()
+    {
+        var ifr = document.createElement("iframe");
+        document.body.appendChild(ifr);
+        this.add_cleanup(() => ifr.remove());
+        assert_throws_dom("SyntaxError", ifr.contentWindow.DOMException,
+                          function () {ifr.contentDocument.querySelector("")});
+    }, "Test throw DOM SyntaxError from subframe");
+
+    test(function()
+    {
+        var ifr = document.createElement("iframe");
+        document.body.appendChild(ifr);
+        this.add_cleanup(() => ifr.remove());
+        assert_throws_dom("SyntaxError",
+                          function () {ifr.contentDocument.querySelector("")});
+    }, "Test throw DOM SyntaxError from subframe with incorrect global expectation; expected to fail");
+
+    test(function()
+    {
+        var ifr = document.createElement("iframe");
+        document.body.appendChild(ifr);
+        this.add_cleanup(() => ifr.remove());
+        assert_throws_dom("SyntaxError", ifr.contentWindow.DOMException,
+                          function () {document.querySelector("")});
+    }, "Test throw DOM SyntaxError with incorrect expectation; expected to fail");
+
+    test(function()
+    {
+        assert_throws_dom("SyntaxError", function () {JSON.parse("{")});
+    }, "Test throw JS SyntaxError where SyntaxError DOMException expected; expected to fail")
+
+    test(function()
+    {
+        var a = document.createTextNode("a")
+        var b = document.createElement("b")
+        assert_throws_dom("NOT_FOUND_ERR", function () {a.appendChild(b)});
+    }, "Test throw DOM exception expected to fail")
+
+    test(function()
+    {
+        var e = new DOMException("I am not known", "TEST_ERROR_NO_SUCH_THING");
+        assert_throws_dom(0, function() {throw e});
+    }, "Test assert_throws_dom with ambiguous DOM-exception expected to Fail");
+
+    test(function()
+    {
+        var e = {code:0, name:"TEST_ERR", TEST_ERR:0};
+        e.constructor = DOMException;
+        assert_throws_dom("TEST_ERR", function() {throw e});
+    }, "Test assert_throws_dom with non-DOM-exception expected to Fail");
+
+    test(function()
+    {
+        var e = {code: DOMException.SYNTAX_ERR, name:"SyntaxError"};
+        e.constructor = DOMException;
+        assert_throws_dom(DOMException.SYNTAX_ERR, function() {throw e});
+    }, "Test assert_throws_dom with number code value expected to Pass");
+
+    test(function()
+    {
+        var e = new DOMException("Some message", "SyntaxError");
+        assert_throws_dom(DOMException.SYNTAX_ERR, function() {throw e});
+    }, "Test assert_throws_dom with number code value and real DOMException expected to Pass");
+
+    var t = async_test("Test step_func")
+    setTimeout(
+      t.step_func(
+        function () {
+          assert_true(true); t.done();
+        }), 0);
+
+    async_test(function(t) {
+        setTimeout(t.step_func(function (){assert_true(true); t.done();}), 0);
+    }, "Test async test with callback");
+
+    async_test(function() {
+        setTimeout(this.step_func(function (){assert_true(true); this.done();}), 0);
+    }, "Test async test with callback and `this` obj.");
+
+    async_test("test should timeout (fail) with the default of 2 seconds").step(function(){});
+
+    async_test("async test that is never started, should have status Not Run");
+
+
+    test(function(t) {
+             window.global = 1;
+             t.add_cleanup(function() {delete window.global});
+             assert_equals(window.global, 1);
+         },
+         "Test that defines a global and cleans it up");
+
+    test(function() {assert_equals(window.global, undefined)},
+         "Test that cleanup handlers from previous test ran");
+
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "TIMEOUT",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Setup function ran",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test assert_throws_dom with ambiguous DOM-exception expected to Fail",
+      "message": "Test bug: ambiguous DOMException code 0 passed to assert_throws_dom()",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test assert_throws_dom with non-DOM-exception expected to Fail",
+      "message": "Test bug: unrecognized DOMException code name or name \"TEST_ERR\" passed to assert_throws_dom()",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test assert_throws_dom with number code value expected to Pass",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test assert_throws_dom with number code value and real DOMException expected to Pass",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test async test with callback",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test async test with callback and `this` obj.",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test step_func",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test that cleanup handlers from previous test ran",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test that defines a global and cleans it up",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test throw DOM exception",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw DOMException as JS exception expected to fail",
+      "message": "assert_throws_js: function \"function DOMException() {\n    [native code]\n}\" is not an Error subtype",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw SyntaxError DOMException where JS SyntaxError expected; expected to fail",
+      "message": "assert_throws_js: function \"function () {document.querySelector(\"\")}\" threw object \"SyntaxError: Document.querySelector: '' is not a valid selector\" (\"SyntaxError\") expected instance of function \"function SyntaxError() {\n    [native code]\n}\" (\"SyntaxError\")",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test throw JS SyntaxError",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test throw DOM SyntaxError",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test throw DOM SyntaxError from subframe",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw DOM SyntaxError from subframe with incorrect global expectation; expected to fail",
+      "message": "assert_throws_dom: function \"function () {ifr.contentDocument.querySelector(\"\")}\" threw an exception from the wrong global",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw DOM SyntaxError with incorrect expectation; expected to fail",
+      "message": "assert_throws_dom: function \"function () {document.querySelector(\"\")}\" threw an exception from the wrong global",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw JS SyntaxError where SyntaxError DOMException expected; expected to fail",
+      "message": "assert_throws_dom: function \"function () {JSON.parse(\"{\")}\" threw object \"SyntaxError: JSON.parse: end of data while reading object contents at line 1 column 2 of the JSON data\" that is not a DOMException SyntaxError: property \"code\" is equal to undefined, expected 12",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Test throw DOM exception expected to fail",
+      "message": "assert_throws_dom: function \"function () {a.appendChild(b)}\" threw object \"HierarchyRequestError: Node.appendChild: Cannot add children to a Text\" that is not a DOMException NOT_FOUND_ERR: property \"code\" is equal to 3, expected 8",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_array_equals with first param 1",
+      "message": "assert_array_equals: 1 equals [1]? value is 1, expected array",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_array_equals with first param false",
+      "message": "assert_array_equals: false equals [1]? value is false, expected array",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_array_equals with first param null",
+      "message": "assert_array_equals: null equals [1]? value is null, expected array",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_array_equals with first param true",
+      "message": "assert_array_equals: true equals [1]? value is true, expected array",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_array_equals with first param undefined",
+      "message": "assert_array_equals: undefined equals [1]? value is undefined, expected array",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_equals tests",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_equals tests expected to fail",
+      "message": "assert_equals: Zero case expected 0 but got -0",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_greater_than expected to fail",
+      "message": "assert_greater_than: 10 is not greater than 11 expected a number greater than 11 but got 10",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_less_than_equal expected to fail",
+      "message": "assert_greater_than_equal: '10' is not a number expected a number but got a \"string\"",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_not_equals tests",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "assert_true expected to fail",
+      "message": "assert_true: false should not be true expected true got false",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true expected to pass",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "async test that is never started, should have status Not Run",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "basic assert_approx_equals test",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "basic assert_array_approx_equals test",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "basic assert_array_equals test",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "basic assert_greater_than_equal test",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "basic assert_less_than test",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "body element fires the onload event set from the attribute",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "document.body should be the first body element in the document",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "test for assert[_not]_own_property and insert_inherits",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "TIMEOUT",
+      "name": "test should timeout (fail) with the default of 2 seconds",
+      "message": "Test timed out",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "window onload event fires when set from the handler",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "on_event does not use event capture",
+      "message": null,
+      "properties": {}
+    }
+  ],
+  "summarized_asserts": [
+    {
+      "assert_name": "assert_true",
+      "test": "Setup function ran",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "on_event does not use event capture",
+      "args": [
+        "[\"inner\", \"outer\"]",
+        "[\"inner\", \"outer\"]"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "document.body should be the first body element in the document",
+      "args": [
+        "Element node <body onload=\"load_test_attr.done()\"> <h1>Sample HTML5 AP...",
+        "Element node <body onload=\"load_test_attr.done()\"> <h1>Sample HTML5 AP..."
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "assert_equals tests",
+      "args": [
+        "1",
+        "1"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "assert_equals tests",
+      "args": [
+        "NaN",
+        "NaN",
+        "\"NaN case\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "assert_equals tests",
+      "args": [
+        "0",
+        "0",
+        "\"Zero case\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "assert_equals tests expected to fail",
+      "args": [
+        "-0",
+        "0",
+        "\"Zero case\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_not_equals",
+      "test": "assert_not_equals tests",
+      "args": [
+        "object \"[object Object]\"",
+        "object \"[object Object]\"",
+        "\"object case\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_not_equals",
+      "test": "assert_not_equals tests",
+      "args": [
+        "-0",
+        "0",
+        "\"Zero case\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "assert_true expected to pass",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "assert_true expected to fail",
+      "args": [
+        "false",
+        "\"false should not be true\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "basic assert_array_equals test",
+      "args": [
+        "[1, NaN]",
+        "[1, NaN]",
+        "\"[1, NaN] is equal to [1, NaN]\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "assert_array_equals with first param undefined",
+      "args": [
+        "undefined",
+        "[1]",
+        "\"undefined equals [1]?\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "assert_array_equals with first param true",
+      "args": [
+        "true",
+        "[1]",
+        "\"true equals [1]?\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "assert_array_equals with first param false",
+      "args": [
+        "false",
+        "[1]",
+        "\"false equals [1]?\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "assert_array_equals with first param null",
+      "args": [
+        "null",
+        "[1]",
+        "\"null equals [1]?\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_equals",
+      "test": "assert_array_equals with first param 1",
+      "args": [
+        "1",
+        "[1]",
+        "\"1 equals [1]?\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_array_approx_equals",
+      "test": "basic assert_array_approx_equals test",
+      "args": [
+        "[10, 11]",
+        "[11, 10]",
+        "1",
+        "\"[10, 11] is approximately (+/- 1) [11, 10]\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_approx_equals",
+      "test": "basic assert_approx_equals test",
+      "args": [
+        "10",
+        "11",
+        "1",
+        "\"10 is approximately (+/- 1) 11\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_approx_equals",
+      "test": "basic assert_less_than test",
+      "args": [
+        "10",
+        "11",
+        "1",
+        "\"10 is approximately (+/- 1) 11\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_greater_than",
+      "test": "assert_greater_than expected to fail",
+      "args": [
+        "10",
+        "11",
+        "\"10 is not greater than 11\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_greater_than_equal",
+      "test": "basic assert_greater_than_equal test",
+      "args": [
+        "10",
+        "10",
+        "\"10 is greater than or equal to 10\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_greater_than_equal",
+      "test": "assert_less_than_equal expected to fail",
+      "args": [
+        "\"10\"",
+        "10",
+        "\"'10' is not a number\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_own_property",
+      "test": "test for assert[_not]_own_property and insert_inherits",
+      "args": [
+        "object \"[object Object]\"",
+        "\"a\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_not_own_property",
+      "test": "test for assert[_not]_own_property and insert_inherits",
+      "args": [
+        "object \"[object Object]\"",
+        "\"b\"",
+        "\"unexpected property found: \\\"b\\\"\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_inherits",
+      "test": "test for assert[_not]_own_property and insert_inherits",
+      "args": [
+        "object \"[object Object]\"",
+        "\"b\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM exception",
+      "args": [
+        "\"NOT_FOUND_ERR\"",
+        "function \"function () {a.removeChild(b)}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_js",
+      "test": "Test throw DOMException as JS exception expected to fail",
+      "args": [
+        "function \"function DOMException() {     [native code] }\"",
+        "function \"function () {a.removeChild(b)}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_js",
+      "test": "Test throw SyntaxError DOMException where JS SyntaxError expected; expected to fail",
+      "args": [
+        "function \"function SyntaxError() {     [native code] }\"",
+        "function \"function () {document.querySelector(\"\")}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_js",
+      "test": "Test throw JS SyntaxError",
+      "args": [
+        "function \"function SyntaxError() {     [native code] }\"",
+        "function \"function () {JSON.parse(\"{\")}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM SyntaxError",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"function () {document.querySelector(\"\")}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM SyntaxError from subframe",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"function DOMException() {     [native code] }\"",
+        "function \"function () {ifr.contentDocument.querySelector(\"\")}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM SyntaxError from subframe with incorrect global expectation; expected to fail",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"function () {ifr.contentDocument.querySelector(\"\")}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM SyntaxError with incorrect expectation; expected to fail",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"function DOMException() {     [native code] }\"",
+        "function \"function () {document.querySelector(\"\")}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw JS SyntaxError where SyntaxError DOMException expected; expected to fail",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"function () {JSON.parse(\"{\")}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test throw DOM exception expected to fail",
+      "args": [
+        "\"NOT_FOUND_ERR\"",
+        "function \"function () {a.appendChild(b)}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test assert_throws_dom with ambiguous DOM-exception expected to Fail",
+      "args": [
+        "0",
+        "function \"function() {throw e}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test assert_throws_dom with non-DOM-exception expected to Fail",
+      "args": [
+        "\"TEST_ERR\"",
+        "function \"function() {throw e}\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test assert_throws_dom with number code value expected to Pass",
+      "args": [
+        "12",
+        "function \"function() {throw e}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Test assert_throws_dom with number code value and real DOMException expected to Pass",
+      "args": [
+        "12",
+        "function \"function() {throw e}\""
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "Test that defines a global and cleans it up",
+      "args": [
+        "1",
+        "1"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_equals",
+      "test": "Test that cleanup handlers from previous test ran",
+      "args": [
+        "undefined",
+        "undefined"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "Test step_func",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "Test async test with callback",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "Test async test with callback and `this` obj.",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/api-tests-2.html b/testing/web-platform/tests/resources/test/tests/functional/api-tests-2.html
new file mode 100644
index 0000000000..9af94f61ac
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/api-tests-2.html
@@ -0,0 +1,62 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Sample HTML5 API Tests</title>
+</head>
+<body>
+<h1>Sample HTML5 API Tests</h1>
+<p>There should be two results</p>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({explicit_done:true})
+test(function() {assert_true(true)}, "Test defined before onload");
+
+onload = function() {test(function (){assert_true(true)}, "Test defined after onload");
+done();
+}
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Test defined after onload",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test defined before onload",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "summarized_asserts": [
+    {
+      "assert_name": "assert_true",
+      "test": "Test defined before onload",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "Test defined after onload",
+      "args": [
+        "true"
+      ],
+      "status": 0
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/api-tests-3.html b/testing/web-platform/tests/resources/test/tests/functional/api-tests-3.html
new file mode 100644
index 0000000000..991fc6da67
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/api-tests-3.html
@@ -0,0 +1,34 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Sample HTML5 API Tests</title>
+</head>
+<script src="/resources/testharness.js"></script>
+
+<body>
+<h1>Sample HTML5 API Tests</h1>
+<div id="log"></div>
+<script>
+setup({explicit_timeout:true});
+var t = async_test("This test should give a status of 'Not Run' without a delay");
+timeout();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "TIMEOUT",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "NOTRUN",
+      "name": "This test should give a status of 'Not Run' without a delay",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/assert-array-equals.html b/testing/web-platform/tests/resources/test/tests/functional/assert-array-equals.html
new file mode 100644
index 0000000000..b6460a4868
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/assert-array-equals.html
@@ -0,0 +1,162 @@
+<!DOCTYPE HTML>
+<title>assert_array_equals</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<script>
+test(() => {
+  assert_array_equals([], []);
+}, "empty and equal");
+test(() => {
+  assert_array_equals([1], [1]);
+}, "non-empty and equal");
+test(() => {
+  assert_array_equals([], [1]);
+}, "length differs");
+test(() => {
+  assert_array_equals([1], [,]);
+}, "property is present");
+test(() => {
+  assert_array_equals([,], [1]);
+}, "property is missing");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20], ["x",1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]);
+}, "property 0 differs");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20], [0,1,2,3,4,"x",6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]);
+}, "property 5 differs");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "lengths differ and input array beyond display limit");
+test(() => {
+  assert_array_equals([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "lengths differ and expected array beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "property 0 is present and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "property 0 is missing and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,,19,20,21]);
+}, "property 18 is present and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,,19,20,21], [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "property 18 is missing and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], ["x",1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "property 0 differs and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21], [0,1,2,3,4,"x",6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]);
+}, "property 5 differs and arrays are beyond display limit");
+test(() => {
+  assert_array_equals([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26], [0,1,2,3,4,5,6,7,8,9,10,11,"x",13,14,15,16,17,18,19,20,21,22,23,24,25,26]);
+}, "property 5 differs and arrays are beyond display limit on both sides");
+</script>
+<script type="text/json" id="expected">
+{
+  "type": "complete",
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "name": "empty and equal",
+      "message": null,
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "name": "length differs",
+      "message": "assert_array_equals: lengths differ, expected array [1] length 1, got [] length 0",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "lengths differ and expected array beyond display limit",
+      "message": "assert_array_equals: lengths differ, expected array [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21] length 22, got [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21] length 21",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "lengths differ and input array beyond display limit",
+      "message": "assert_array_equals: lengths differ, expected array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21] length 21, got [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21] length 22",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "non-empty and equal",
+      "message": null,
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "name": "property 0 differs",
+      "message": "assert_array_equals: expected property 0 to be \"x\" but got 0 (expected array [\"x\", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] got [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 0 differs and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 0 to be \"x\" but got 0 (expected array [\"x\", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026] got [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 0 is missing and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 0 to be \"present\" but was \"missing\" (expected array [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026] got [, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 0 is present and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 0 to be \"missing\" but was \"present\" (expected array [, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026] got [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 18 is missing and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 18 to be \"present\" but was \"missing\" (expected array [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21] got [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, , 19, 20, 21])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 18 is present and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 18 to be \"missing\" but was \"present\" (expected array [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, , 19, 20, 21] got [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 5 differs",
+      "message": "assert_array_equals: expected property 5 to be \"x\" but got 5 (expected array [0, 1, 2, 3, 4, \"x\", 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20] got [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 5 differs and arrays are beyond display limit",
+      "message": "assert_array_equals: expected property 5 to be \"x\" but got 5 (expected array [0, 1, 2, 3, 4, \"x\", 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026] got [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, \u2026])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property 5 differs and arrays are beyond display limit on both sides",
+      "message": "assert_array_equals: expected property 12 to be \"x\" but got 12 (expected array [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, \"x\", 13, 14, 15, 16, 17, 18, 19, 20, 21, \u2026] got [\u2026, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, \u2026])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property is missing",
+      "message": "assert_array_equals: expected property 0 to be \"present\" but was \"missing\" (expected array [1] got [])",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "name": "property is present",
+      "message": "assert_array_equals: expected property 0 to be \"missing\" but was \"present\" (expected array [] got [1])",
+      "properties": {},
+      "status_string": "FAIL"
+    }
+  ]
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/assert-throws-dom.html b/testing/web-platform/tests/resources/test/tests/functional/assert-throws-dom.html
new file mode 100644
index 0000000000..4dd66b2372
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/assert-throws-dom.html
@@ -0,0 +1,55 @@
+<!DOCTYPE HTML>
+<title>assert_throws_dom</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="log"></div>
+<script>
+test(() => {
+  function f() {
+      assert_true(false, "Trivial assertion.");
+
+      // Would lead to throwing a SyntaxError.
+      document.createElement("div").contentEditable = "invalid";
+    }
+
+  assert_throws_dom("SyntaxError", () => { f(); });
+}, "Violated assertion nested in `assert_throws_dom`.");
+</script>
+<script type="text/json" id="expected">
+{
+  "type": "complete",
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "message": "assert_true: Trivial assertion. expected true got false",
+      "name": "Violated assertion nested in `assert_throws_dom`.",
+      "properties": {},
+      "status_string": "FAIL"
+    }
+  ],
+  "summarized_asserts": [
+    {
+      "assert_name": "assert_throws_dom",
+      "test": "Violated assertion nested in `assert_throws_dom`.",
+      "args": [
+        "\"SyntaxError\"",
+        "function \"() => { f(); }\""
+      ],
+      "status": 1
+    },
+    {
+      "assert_name": "assert_true",
+      "test": "Violated assertion nested in `assert_throws_dom`.",
+      "args": [
+        "false",
+        "\"Trivial assertion.\""
+      ],
+      "status": 1
+    }
+  ]
+}
+</script>
+
diff --git a/testing/web-platform/tests/resources/test/tests/functional/force_timeout.html b/testing/web-platform/tests/resources/test/tests/functional/force_timeout.html
new file mode 100644
index 0000000000..2058fdb862
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/force_timeout.html
@@ -0,0 +1,60 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test#force_timeout</title>
+</head>
+<body>
+<h1>Test#force_timeout</h1>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({ explicit_timeout: true });
+
+test(function(t) {
+    t.force_timeout();
+  }, 'test (synchronous)');
+
+async_test(function(t) {
+    t.step_timeout(function() {
+        t.force_timeout();
+      }, 0);
+  }, 'async_test');
+
+promise_test(function(t) {
+    t.force_timeout();
+
+    return new Promise(function() {});
+  }, 'promise_test');
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "TIMEOUT",
+      "name": "async_test",
+      "message": "Test timed out",
+      "properties": {}
+    },
+    {
+      "status_string": "TIMEOUT",
+      "name": "promise_test",
+      "message": "Test timed out",
+      "properties": {}
+    },
+    {
+      "status_string": "TIMEOUT",
+      "name": "test (synchronous)",
+      "message": "Test timed out",
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/generate-callback.html b/testing/web-platform/tests/resources/test/tests/functional/generate-callback.html
new file mode 100644
index 0000000000..11d41743b3
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/generate-callback.html
@@ -0,0 +1,153 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Sample for using generate_tests to create a series of tests that share the same callback.</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<script>
+// generate_tests takes an array of arrays that define tests
+// but lets pass it an empty array and verify it does nothing.
+function null_callback() {
+  throw "null_callback should not be called.";
+}
+generate_tests(null_callback, []);
+
+// Generate 3 tests specifying the name and one parameter
+function validate_arguments(arg1) {
+  assert_equals(arg1, 1, "Ensure that we get our expected argument");
+}
+generate_tests(validate_arguments, [
+  ["first test", 1],
+  ["second test", 1],
+  ["third test", 1],
+]);
+
+// Generate a test passing in a properties object that is shared across tests.
+function validate_properties() {
+  assert_true(this.properties.sentinel, "Ensure that we got the right properties object.");
+}
+generate_tests(validate_properties, [["sentinel check 1"], ["sentinel check 2"]], {sentinel: true});
+
+// Generate a test passing in a properties object that is shared across tests.
+function validate_separate_properties() {
+  if (this.name === "sentinel check 1 unique properties") {
+    assert_true(this.properties.sentinel, "Ensure that we got the right properties object. Expect sentinel: true.");
+  }
+  else {
+    assert_false(this.properties.sentinel, "Ensure that we got the right properties object. Expect sentinel: false.");
+  }
+}
+generate_tests(validate_separate_properties, [["sentinel check 1 unique properties"], ["sentinel check 2 unique properties"]], [{sentinel: true}, {sentinel: false}]);
+
+// Finally generate a complicated set of tests from another data source
+var letters = ["a", "b", "c", "d", "e", "f"];
+var numbers = [0, 1, 2, 3, 4, 5];
+function validate_related_arguments(arg1, arg2) {
+  assert_equals(arg1.charCodeAt(0) - "a".charCodeAt(0), arg2, "Ensure that we can map letters to numbers.");
+}
+function format_as_test(letter, index, letters) {
+  return ["Test to map " + letter + " to " + numbers[index], letter, numbers[index]];
+}
+generate_tests(validate_related_arguments, letters.map(format_as_test));
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Test to map a to 0",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test to map b to 1",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test to map c to 2",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test to map d to 3",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test to map e to 4",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test to map f to 5",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "first test",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "second test",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "sentinel check 1",
+      "properties": {
+        "sentinel": true
+      },
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "sentinel check 1 unique properties",
+      "properties": {
+        "sentinel": true
+      },
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "sentinel check 2",
+      "properties": {
+        "sentinel": true
+      },
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "sentinel check 2 unique properties",
+      "properties": {
+        "sentinel": false
+      },
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "third test",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlDictionary/test_partial_interface_of.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlDictionary/test_partial_interface_of.html
new file mode 100644
index 0000000000..05e6e0b1e0
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlDictionary/test_partial_interface_of.html
@@ -0,0 +1,90 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <meta name="variant" content="">
+  <title>idlharness: Partial dictionary</title>
+  <script src="/resources/test/variants.js"></script>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+
+<body>
+  <p>Verify the series of sub-tests that are executed for "partial" dictionary objects.</p>
+  <script>
+    "use strict";
+
+    // No original existence
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls('partial dictionary A {};');
+      idlArray.test();
+    })();
+
+    // Multiple partials existence
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls('partial dictionary B {};');
+      idlArray.add_idls('partial dictionary B {};');
+      idlArray.add_idls('partial dictionary B {};');
+      idlArray.add_idls('partial dictionary B {};');
+      idlArray.add_idls('dictionary B {};');
+      idlArray.test();
+    })();
+
+    // Original is a namespace, not a dictionary.
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        partial dictionary C {};
+        namespace C {};`);
+      idlArray.merge_partials();
+    })();
+  </script>
+  <script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "Partial dictionary A: original dictionary defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original dictionary should be defined expected true got false"
+    },
+    {
+      "name": "Partial dictionary B[2]: original dictionary defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial dictionary B[3]: original dictionary defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial dictionary B[4]: original dictionary defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial dictionary C: original dictionary defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original C definition should have type dictionary expected true got false"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_exposed_wildcard.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_exposed_wildcard.html
new file mode 100644
index 0000000000..addc0eb4fc
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_exposed_wildcard.html
@@ -0,0 +1,233 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: Exposed=*</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+<body>
+<script>
+"use strict";
+
+Object.defineProperty(window, "A", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: function A() {}
+  });
+Object.defineProperty(window.A, "prototype", {
+    writable: false,
+    value: window.A.prototype
+  });
+A.prototype[Symbol.toStringTag] = "A";
+
+Object.defineProperty(window, "C", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: function C() {}
+  });
+Object.defineProperty(window.C, "prototype", {
+    writable: false,
+    value: window.C.prototype
+  });
+C.prototype[Symbol.toStringTag] = "C";
+
+Object.defineProperty(window, "D", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: function D() {}
+  });
+Object.defineProperty(window.D, "prototype", {
+    writable: false,
+    value: window.D.prototype
+  });
+C.prototype[Symbol.toStringTag] = "D";
+Object.defineProperty(window, "B", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: window.A
+  });
+
+var idlArray = new IdlArray();
+idlArray.add_idls(`
+[Exposed=*, LegacyWindowAlias=B] interface A {};
+[Exposed=*] partial interface A {};
+[Exposed=Window] interface C {};
+[Exposed=*] partial interface C {};
+[Exposed=*] interface D {};
+[Exposed=Window] partial interface D {};
+`);
+idlArray.add_objects({
+  Window: ["window"]
+});
+idlArray.test();
+</script>
+<script type="text/json" id="expected">
+{
+    "summarized_status": {
+        "message": null,
+        "status_string": "OK"
+    },
+    "summarized_tests": [
+        {
+            "name": "A interface object length",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "A interface object name",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "A interface: existence and properties of interface object",
+            "properties": {},
+            "message": "assert_throws_js: interface object didn't throw TypeError when called as a function function \"function() {\n            interface_object();\n        }\" did not throw",
+            "status_string": "FAIL"
+        },
+        {
+            "name": "A interface: existence and properties of interface prototype object",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "A interface: existence and properties of interface prototype object's \"constructor\" property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "A interface: existence and properties of interface prototype object's @@unscopables property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "A interface: legacy window alias",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "C interface object length",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "C interface object name",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "C interface: existence and properties of interface object",
+            "properties": {},
+            "message": "assert_throws_js: interface object didn't throw TypeError when called as a function function \"function() {\n            interface_object();\n        }\" did not throw",
+            "status_string": "FAIL"
+        },
+        {
+            "name": "C interface: existence and properties of interface prototype object",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "C interface: existence and properties of interface prototype object's \"constructor\" property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "C interface: existence and properties of interface prototype object's @@unscopables property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "D interface object length",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "D interface object name",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "D interface: existence and properties of interface object",
+            "properties": {},
+            "message": "assert_throws_js: interface object didn't throw TypeError when called as a function function \"function() {\n            interface_object();\n        }\" did not throw",
+            "status_string": "FAIL"
+        },
+        {
+            "name": "D interface: existence and properties of interface prototype object",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "D interface: existence and properties of interface prototype object's \"constructor\" property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "D interface: existence and properties of interface prototype object's @@unscopables property",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "Partial interface A: original interface defined",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "Partial interface A: valid exposure set",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "Partial interface C: original interface defined",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "Partial interface C: valid exposure set",
+            "properties": {},
+            "message": "Partial C interface is exposed everywhere, the original interface is not.",
+            "status_string": "FAIL"
+        },
+        {
+            "name": "Partial interface D: original interface defined",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        },
+        {
+            "name": "Partial interface D: valid exposure set",
+            "properties": {},
+            "message": null,
+            "status_string": "PASS"
+        }
+    ],
+    "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_immutable_prototype.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_immutable_prototype.html
new file mode 100644
index 0000000000..5fe05915b0
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_immutable_prototype.html
@@ -0,0 +1,298 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: Immutable prototypes</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+<body>
+<script>
+"use strict";
+
+Object.defineProperty(window, "Foo", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: function Foo() {
+        if (!new.target) {
+            throw new TypeError('Foo() must be called with new');
+        }
+    }
+  });
+Object.defineProperty(window.Foo, "prototype", {
+    writable: false,
+    value: window.Foo.prototype
+  });
+Foo.prototype[Symbol.toStringTag] = "Foo";
+
+var idlArray = new IdlArray();
+idlArray.add_untested_idls("interface EventTarget {};");
+idlArray.add_idls(
+    "[Global=Window, Exposed=Window]\n" +
+    "interface Window : EventTarget {};\n" +
+
+    "[Global=Window, Exposed=Window]\n" +
+    "interface Foo { constructor(); };"
+  );
+idlArray.add_objects({
+  Foo: ["new Foo()"],
+  Window: ["window"]
+});
+idlArray.test();
+</script>
+<script type="text/json" id="expected">
+{
+    "summarized_status": {
+        "message": null,
+        "status_string": "OK"
+    },
+    "summarized_tests": [
+        {
+            "name": "Foo interface object length",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface object name",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: existence and properties of interface object",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: existence and properties of interface prototype object",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: existence and properties of interface prototype object's \"constructor\" property",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: existence and properties of interface prototype object's @@unscopables property",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via Object.setPrototypeOf should throw a TypeError",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_throws_js: function \"function() {\n            Object.setPrototypeOf(obj, newValue);\n        }\" did not throw"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via Reflect.setPrototypeOf should return false",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_false: expected false got true"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via __proto__ should throw a TypeError",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_throws_js: function \"function() {\n            obj.__proto__ = newValue;\n        }\" did not throw"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via Object.setPrototypeOf should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via Reflect.setPrototypeOf should return true",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via __proto__ should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via Object.setPrototypeOf should throw a TypeError",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_throws_js: function \"function() {\n            Object.setPrototypeOf(obj, newValue);\n        }\" did not throw"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via Reflect.setPrototypeOf should return false",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_false: expected false got true"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via __proto__ should throw a TypeError",
+            "status_string": "FAIL",
+            "properties": {},
+            "message": "assert_throws_js: function \"function() {\n            obj.__proto__ = newValue;\n        }\" did not throw"
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via Object.setPrototypeOf should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via Reflect.setPrototypeOf should return true",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via __proto__ should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Foo must be primary interface of new Foo()",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Stringification of new Foo()",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Stringification of window",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface object length",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface object name",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: existence and properties of interface object",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: existence and properties of interface prototype object",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: existence and properties of interface prototype object's \"constructor\" property",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: existence and properties of interface prototype object's @@unscopables property",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via Object.setPrototypeOf should throw a TypeError",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via Reflect.setPrototypeOf should return false",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to a new value via __proto__ should throw a TypeError",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via Object.setPrototypeOf should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via Reflect.setPrototypeOf should return true",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of global platform object - setting to its original value via __proto__ should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via Object.setPrototypeOf should throw a TypeError",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via Reflect.setPrototypeOf should return false",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to a new value via __proto__ should throw a TypeError",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via Object.setPrototypeOf should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via Reflect.setPrototypeOf should return true",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window interface: internal [[SetPrototypeOf]] method of interface prototype object - setting to its original value via __proto__ should not throw",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        },
+        {
+            "name": "Window must be primary interface of window",
+            "status_string": "PASS",
+            "properties": {},
+            "message": null
+        }
+    ],
+    "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_interface_mixin.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_interface_mixin.html
new file mode 100644
index 0000000000..be2844e698
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_interface_mixin.html
@@ -0,0 +1,131 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: interface mixins</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+
+<body>
+  <p>Verify the series of sub-tests that are executed for "interface mixin" objects.</p>
+  <script>
+    "use strict";
+
+    // Simple includes statement (valid)
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        [Exposed=Window] interface I1 {};
+        interface mixin M1 { attribute any a1; };
+        I1 includes M1;`);
+      idlArray.merge_partials();
+      idlArray.merge_mixins();
+    })();
+
+    // Partial interface mixin (valid)
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        [Exposed=Window] interface I2 {};
+        interface mixin M2 {};
+        partial interface mixin M2 { attribute any a2; };
+        I2 includes M2;`);
+      idlArray.merge_partials();
+      idlArray.merge_mixins();
+    })();
+
+    // Partial interface mixin without original mixin
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls('partial interface mixin M3 {};');
+      idlArray.merge_partials();
+      idlArray.merge_mixins();
+    })();
+
+    // Name clash between mixin and partial mixin
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        interface mixin M4 { attribute any a4; };
+        partial interface mixin M4 { attribute any a4; };`);
+      idlArray.merge_partials();
+      idlArray.merge_mixins();
+    })();
+
+    // Name clash between interface and mixin
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls(`
+        interface mixin M5 { attribute any a5; };
+        interface I5 { attribute any a5; };
+        I5 includes M5;`);
+      idlArray.merge_partials();
+      idlArray.merge_mixins();
+    })();
+  </script>
+  <script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "I1 includes M1: member names are unique",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "I2 includes M2: member names are unique",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "I5 includes M5: member names are unique",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: member a5 is unique expected true got false"
+    },
+    {
+      "name": "Partial interface mixin M2: member names are unique",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface mixin M2: original interface mixin defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface mixin M3: original interface mixin defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original interface mixin should be defined expected true got false"
+    },
+    {
+      "name": "Partial interface mixin M4: member names are unique",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: member a4 is unique expected true got false"
+    },
+    {
+      "name": "Partial interface mixin M4: original interface mixin defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_partial_interface_of.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_partial_interface_of.html
new file mode 100644
index 0000000000..671196cc5d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_partial_interface_of.html
@@ -0,0 +1,188 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <meta name="variant" content="">
+  <title>idlharness: Partial interface</title>
+  <script src="/resources/test/variants.js"></script>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+
+<body>
+  <p>Verify the series of sub-tests that are executed for "partial" interface objects.</p>
+  <script>
+    "use strict";
+
+    // No original existence
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls('partial interface A {};');
+      idlArray.test();
+    })();
+
+    // Valid exposure (Note: Worker -> {Shared,Dedicated,Service}Worker)
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls(`
+        [Exposed=(Worker)]
+        interface B {};
+
+        [Exposed=(DedicatedWorker, ServiceWorker, SharedWorker)]
+        interface C {};`);
+      idlArray.add_idls(`
+        [Exposed=(DedicatedWorker, ServiceWorker, SharedWorker)]
+        partial interface B {};
+
+        [Exposed=(Worker)]
+        partial interface C {};`);
+      idlArray.merge_partials();
+    })();
+
+    // Invalid exposure
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls(`
+        [Exposed=(Window, ServiceWorker)]
+        interface D {};`);
+      idlArray.add_idls(`
+        [Exposed=(DedicatedWorker)]
+        partial interface D {};`);
+      idlArray.merge_partials();
+    })();
+
+    // Original is a namespace, not an interface.
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        partial interface E {};
+        namespace E {};`);
+      idlArray.merge_partials();
+    })();
+
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        partial interface F {};
+        partial interface mixin G {};
+      `);
+      idlArray.add_dependency_idls(`
+        interface F {};
+        interface mixin G {};
+        interface mixin H {};
+        F includes H;
+        I includes H;
+        J includes G;
+        interface K : J {};
+        interface L : F {};
+      `);
+      test(() => {
+        // Convert idlArray.includes into a Map from name of target interface to
+        // name of included mixin. (This assumes each interface includes at most
+        // one mixin, otherwise later includes would clobber earlier ones.)
+        const includes = new Map(idlArray.includes.map(i => [i.target, i.includes]));
+        // F is tested, so H is a dep.
+        assert_equals(includes.get('F'), 'H', 'F should be picked up');
+        // H is not tested, so I is not a dep.
+        assert_false(includes.has('I'), 'I should be ignored');
+        // G is a dep, so J is a dep.
+        assert_equals(includes.get('J'), 'G', 'J should be picked up');
+        // K isn't a dep because J isn't defined.
+        assert_false('K' in idlArray.members, 'K should be ignored');
+        // L isn't a dep because F is untested.
+        assert_false('L' in idlArray.members, 'L should be ignored');
+      }, 'partial mixin dep implications');
+    })();
+
+    // Name clash (partials)
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        interface M { attribute any A; };
+        partial interface M { attribute any A; };`);
+      idlArray.merge_partials();
+    })();
+  </script>
+  <script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "Partial interface A: original interface defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original interface should be defined expected true got false"
+    },
+    {
+      "name": "Partial interface B: original interface defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface B: valid exposure set",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface C: original interface defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface C: valid exposure set",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface D: original interface defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface D: valid exposure set",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "Partial D interface is exposed to 'DedicatedWorker', the original interface is not."
+    },
+    {
+      "name": "Partial interface E: original interface defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original E definition should have type interface expected true got false"
+    },
+    {
+      "name": "partial mixin dep implications",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface M: original interface defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial interface M: member names are unique",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: member A is unique expected true got false"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_primary_interface_of.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_primary_interface_of.html
new file mode 100644
index 0000000000..309de60bb7
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_primary_interface_of.html
@@ -0,0 +1,116 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: Primary interface</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+<body>
+<p>Verify the series of sub-tests that are executed for "tested" interface
+objects but skipped for "untested" interface objects.</p>
+<script>
+"use strict";
+
+function FooParent() {
+    if (!new.target) {
+        throw new TypeError('FooParent() must be called with new');
+    }
+}
+Object.defineProperty(window, "Foo", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: function Foo() {
+        if (!new.target) {
+            throw new TypeError('Foo() must be called with new');
+        }
+    }
+  });
+Object.defineProperty(window.Foo, "prototype", {
+    writable: false,
+    value: new FooParent()
+  });
+Object.defineProperty(window.Foo.prototype, "constructor", {
+    enumerable: false,
+    writable: true,
+    configurable: true,
+    value: window.Foo
+  });
+Object.setPrototypeOf(Foo, FooParent);
+Foo.prototype[Symbol.toStringTag] = "Foo";
+
+var idlArray = new IdlArray();
+idlArray.add_untested_idls("interface FooParent {};");
+idlArray.add_idls(
+    "interface Foo : FooParent { constructor(); };"
+  );
+idlArray.add_objects({
+  Foo: ["new Foo()"],
+  FooParent: ["new FooParent()"]
+});
+idlArray.test();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "Foo interface object length",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo interface object name",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo interface: existence and properties of interface object",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo interface: existence and properties of interface prototype object",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo interface: existence and properties of interface prototype object's \"constructor\" property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo interface: existence and properties of interface prototype object's @@unscopables property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Foo must be primary interface of new Foo()",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Stringification of new Foo()",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_to_json_operation.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_to_json_operation.html
new file mode 100644
index 0000000000..bbc502a313
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_to_json_operation.html
@@ -0,0 +1,177 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>IdlInterface.prototype.test_to_json_operation()</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+  <script src="../../../../idl-helper.js"></script>
+</head>
+<body>
+<script>
+    "use strict";
+    function wrap(member, obj) {
+        function F(obj) {
+            this._obj = obj;
+        }
+
+        F.prototype.toJSON = function() {
+            return this._obj;
+        }
+        Object.defineProperty(F, 'name', { value: member.name });
+        return new F(obj);
+    }
+
+    var i, obj;
+    i = interfaceFrom("interface A { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, { foo: 123 }), i.members[0]);
+
+    // should fail (wrong type)
+    i = interfaceFrom("interface B { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, { foo: "a value" }), i.members[0]);
+
+    // should handle extraneous attributes (e.g. from an extension specification)
+    i = interfaceFrom("interface C { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, { foo: 123, bar: 456 }), i.members[0]);
+
+    // should fail (missing property)
+    i = interfaceFrom("interface D { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, { }), i.members[0]);
+
+    // should fail (should be writable)
+    obj = Object.defineProperties({}, { foo: {
+        writable: false,
+        enumerable: true,
+        configurable: true,
+        value: 123
+    }});
+    i = interfaceFrom("interface F { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, obj), i.members[0]);
+
+    // should fail (should be enumerable)
+    obj = Object.defineProperties({}, { foo: {
+        writable: true,
+        enumerable: false,
+        configurable: true,
+        value: 123
+    }});
+    i = interfaceFrom("interface G { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, obj), i.members[0]);
+
+    // should fail (should be configurable)
+    obj = Object.defineProperties({}, { foo: {
+        writable: true,
+        enumerable: true,
+        configurable: false,
+        value: 123
+    }});
+    i = interfaceFrom("interface H { [Default] object toJSON(); attribute long foo; };");
+    i.test_to_json_operation("object", wrap(i, obj), i.members[0]);
+
+    var idl = new IdlArray();
+    idl.add_idls("interface I : J { [Default] object toJSON(); attribute long foo; };");
+    idl.add_idls("interface J { [Default] object toJSON(); attribute DOMString foo;};");
+    var i = idl.members.I;
+    i.test_to_json_operation("object", wrap(i, { foo: 123 }), i.members[0]);
+
+    i = interfaceFrom("interface K { [Default] object toJSON(); };");
+    i.test_to_json_operation("object", wrap(i, {}), i.members[0]);
+
+    i = interfaceFrom("interface L { DOMString toJSON(); };");
+    i.test_to_json_operation("object", wrap(i, "a string"), i.members[0]);
+
+    // should fail (wrong output type)
+    i = interfaceFrom("interface M { DOMString toJSON(); };");
+    i.test_to_json_operation("object", wrap(i, {}), i.members[0]);
+
+    // should fail (not an IDL type)
+    i = interfaceFrom("interface N { DOMException toJSON(); };");
+    i.test_to_json_operation("object", wrap(i, {}), i.members[0]);
+</script>
+<script type="text/json" id="expected">
+    {
+        "summarized_status": {
+            "message": null,
+            "status_string": "OK"
+        },
+        "summarized_tests": [
+            {
+                "message": null,
+                "name": "A interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "PASS"
+            },
+            {
+                "message": "assert_equals: expected \"number\" but got \"string\"",
+                "name": "B interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": null,
+                "name": "C interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "PASS"
+            },
+            {
+                "message": "assert_true: property \"foo\" should be present in the output of D.prototype.toJSON() expected true got false",
+                "name": "D interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": "assert_true: property foo should be writable expected true got false",
+                "name": "F interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": "assert_true: property foo should be enumerable expected true got false",
+                "name": "G interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": "assert_true: property foo should be configurable expected true got false",
+                "name": "H interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": null,
+                "name": "I interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "PASS"
+            },
+            {
+                "message": null,
+                "name": "K interface: default toJSON operation on object",
+                "properties": {},
+                "status_string": "PASS"
+            },
+            {
+                "message": null,
+                "name": "L interface: toJSON operation on object",
+                "properties": {},
+                "status_string": "PASS"
+            },
+            {
+                "message": "assert_equals: expected \"string\" but got \"object\"",
+                "name": "M interface: toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            },
+            {
+                "message": "assert_true: {\"type\":\"return-type\",\"extAttrs\":[],\"generic\":\"\",\"nullable\":false,\"union\":false,\"idlType\":\"DOMException\"} is not an appropriate return value for the toJSON operation of N expected true got false",
+                "name": "N interface: toJSON operation on object",
+                "properties": {},
+                "status_string": "FAIL"
+            }
+        ],
+        "type": "complete"
+    }
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_attribute.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_attribute.html
new file mode 100644
index 0000000000..2c94061fc1
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_attribute.html
@@ -0,0 +1,100 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: namespace attribute</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+<body>
+<p>Verify the series of sub-tests that are executed for namespace attributes.</p>
+<script>
+"use strict";
+
+Object.defineProperty(self, "foo", {
+  value: {
+    truth: true,
+  },
+  writable: true,
+  enumerable: false,
+  configurable: true,
+});
+
+var idlArray = new IdlArray();
+idlArray.add_idls(`
+[Exposed=Window]
+namespace foo {
+  readonly attribute bool truth;
+  readonly attribute bool lies;
+};`);
+idlArray.test();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "foo namespace: extended attributes",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: property descriptor",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: [[Extensible]] is true",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: [[Prototype]] is Object.prototype",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: typeof is \"object\"",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: has no length property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: has no name property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: attribute truth",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: attribute lies",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_own_property: foo does not have property \"lies\" expected property \"lies\" missing"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_operation.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_operation.html
new file mode 100644
index 0000000000..da70c8fa31
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_operation.html
@@ -0,0 +1,242 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: namespace operation</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+<body>
+<p>Verify the series of sub-tests that are executed for namespace operations.</p>
+<script>
+"use strict";
+
+Object.defineProperty(self, "foo", {
+  value: Object.defineProperty({}, "Truth", {
+    value: function() {},
+    writable: true,
+    enumerable: true,
+    configurable: true,
+  }),
+  writable: true,
+  enumerable: false,
+  configurable: true,
+});
+
+Object.defineProperty(self, "bar", {
+  value: Object.defineProperty({}, "Truth", {
+    value: function() {},
+    writable: false,
+    enumerable: true,
+    configurable: false,
+  }),
+  writable: true,
+  enumerable: false,
+  configurable: true,
+});
+
+Object.defineProperty(self, "baz", {
+  value: {
+    LongStory: function(hero, ...details) {
+      return `${hero} went and ${details.join(', then')}`
+    },
+    ShortStory: function(...details) {
+      return `${details.join('. ')}`;
+    },
+  },
+  writable: true,
+  enumerable: false,
+  configurable: true,
+});
+
+var idlArray = new IdlArray();
+idlArray.add_idls(`
+[Exposed=Window]
+namespace foo {
+  undefined Truth();
+  undefined Lies();
+};
+[Exposed=Window]
+namespace bar {
+  [LegacyUnforgeable]
+  undefined Truth();
+};
+[Exposed=Window]
+namespace baz {
+  DOMString LongStory(any hero, DOMString... details);
+  DOMString ShortStory(DOMString... details);
+};`);
+idlArray.test();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "foo namespace: extended attributes",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: property descriptor",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: [[Extensible]] is true",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: [[Prototype]] is Object.prototype",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: typeof is \"object\"",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: has no length property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: has no name property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: operation Truth()",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "foo namespace: operation Lies()",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_own_property: namespace object missing operation \"Lies\" expected property \"Lies\" missing"
+    },
+    {
+      "name": "bar namespace: extended attributes",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: property descriptor",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: [[Extensible]] is true",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: [[Prototype]] is Object.prototype",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: typeof is \"object\"",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: has no length property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: has no name property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "bar namespace: operation Truth()",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+
+    {
+      "name": "baz namespace: extended attributes",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: property descriptor",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: [[Extensible]] is true",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: [[Prototype]] is Object.prototype",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: typeof is \"object\"",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: has no length property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: has no name property",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: operation LongStory(any, DOMString...)",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "baz namespace: operation ShortStory(DOMString...)",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_partial_namespace.html b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_partial_namespace.html
new file mode 100644
index 0000000000..eabdcd10a9
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_partial_namespace.html
@@ -0,0 +1,125 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: Partial namespace</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+</head>
+
+<body>
+  <p>Verify the series of sub-tests that are executed for "partial" namespace objects.</p>
+  <script>
+    "use strict";
+
+    // No original existence
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls('partial namespace A {};');
+      idlArray.test();
+    })();
+
+    // Valid exposure (Note: Worker -> {Shared,Dedicated,Service}Worker)
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls(`
+        [Exposed=(Worker)]
+        namespace B {};
+
+        [Exposed=(DedicatedWorker, ServiceWorker, SharedWorker)]
+        namespace C {};`);
+      idlArray.add_idls(`
+        [Exposed=(DedicatedWorker, ServiceWorker, SharedWorker)]
+        partial namespace B {};
+
+        [Exposed=(Worker)]
+        partial namespace C {};`);
+      idlArray.merge_partials();
+    })();
+
+    // Invalid exposure
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_untested_idls(`
+        [Exposed=(Window, ServiceWorker)]
+        namespace D {};`);
+      idlArray.add_idls(`
+        [Exposed=(DedicatedWorker)]
+        partial namespace D {};`);
+      idlArray.merge_partials();
+    })();
+
+    // Original is an interface, not a namespace.
+    (() => {
+      const idlArray = new IdlArray();
+      idlArray.add_idls(`
+        partial namespace E {};
+        interface E {};`);
+      idlArray.merge_partials();
+    })();
+  </script>
+  <script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "name": "Partial namespace A: original namespace defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original namespace should be defined expected true got false"
+    },
+    {
+      "name": "Partial namespace B: original namespace defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial namespace B: valid exposure set",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial namespace C: original namespace defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial namespace C: valid exposure set",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial namespace D: original namespace defined",
+      "status_string": "PASS",
+      "properties": {},
+      "message": null
+    },
+    {
+      "name": "Partial namespace D: valid exposure set",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "Partial D namespace is exposed to 'DedicatedWorker', the original namespace is not."
+    },
+    {
+      "name": "Partial namespace E: original namespace defined",
+      "status_string": "FAIL",
+      "properties": {},
+      "message": "assert_true: Original E definition should have type namespace expected true got false"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/iframe-callback.html b/testing/web-platform/tests/resources/test/tests/functional/iframe-callback.html
new file mode 100644
index 0000000000..f49d0aa6b8
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/iframe-callback.html
@@ -0,0 +1,116 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with iframe that notifies containing document via callbacks</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body onload="start_test_in_iframe()">
+<h1>Callbacks From Tests Running In An IFRAME</h1>
+<p>A test is run inside an <tt>iframe</tt> with a same origin document. The
+containing document should receive callbacks as the tests progress inside the
+<tt>iframe</tt>. A single passing test is expected in the summary below.
+<div id="log"></div>
+
+<script>
+var callbacks = [];
+var START = 1
+var TEST_STATE = 2
+var RESULT = 3
+var COMPLETION = 4
+var test_complete = false;
+
+setup({explicit_done: true});
+
+// The following callbacks are called for tests in this document as well as the
+// tests in the IFRAME. Currently, callbacks invoked from this document and any
+// child document are indistinguishable from each other.
+
+function start_callback(properties) {
+    callbacks.push(START);
+}
+
+function test_state_callback(test) {
+    callbacks.push(TEST_STATE);
+}
+
+function result_callback(test) {
+    callbacks.push(RESULT);
+}
+
+function completion_callback(tests, status) {
+    if (test_complete) {
+        return;
+    }
+    test_complete = true;
+    callbacks.push(COMPLETION);
+    verify_received_callbacks();
+    done();
+}
+
+function verify_received_callbacks() {
+    var copy_of_callbacks = callbacks.slice(0);
+
+    // Note that you can't run test assertions directly in a callback even if
+    // this is a file test. When the callback is invoked from a same-origin child
+    // page, the callstack reaches into the calling child document. Any
+    // exception thrown in a callback will be handled by the child rather than
+    // this document.
+    test(
+        function() {
+            // callbacks list should look like:
+            //     START 1*(TEST_STATE) RESULT COMPLETION
+            assert_equals(copy_of_callbacks.shift(), START,
+                          "The first received callback should be 'start_callback'.");
+            assert_equals(copy_of_callbacks.shift(), TEST_STATE,
+                          "'test_state_callback' should be received before any " +
+                          "result or completion callbacks.");
+            while(copy_of_callbacks.length > 0) {
+                var callback = copy_of_callbacks.shift();
+                if (callback != TEST_STATE) {
+                    copy_of_callbacks.unshift(callback);
+                    break;
+                }
+            }
+            assert_equals(copy_of_callbacks.shift(), RESULT,
+                          "'test_state_callback' should be followed by 'result_callback'.");
+            assert_equals(copy_of_callbacks.shift(), COMPLETION,
+                          "Final 'result_callback' should be followed by 'completion_callback'.");
+            assert_equals(copy_of_callbacks.length, 0,
+                          "'completion_callback' should be the last callback.");
+        });
+}
+
+function start_test_in_iframe() {
+    // This document is going to clear any received callbacks and maintain
+    // radio silence until the test in the iframe runs to completion. The
+    // completion_callback() will then complete the testing on this document.
+    callbacks.length = 0;
+    var iframe = document.createElement("iframe");
+    // single-page-test-pass.html has a single test.
+    iframe.src = "single-page-test-pass.html";
+    iframe.style.setProperty("display", "none");
+    document.getElementById("target").appendChild(iframe);
+}
+</script>
+
+<div id="target">
+</div>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Example with iframe that notifies containing document via callbacks",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-errors.html b/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-errors.html
new file mode 100644
index 0000000000..ef9b8702ec
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-errors.html
@@ -0,0 +1,50 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with iframe that consolidates errors via fetch_tests_from_window</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+var parent_test = async_test("Test executing in parent context");
+</script>
+</head>
+<body onload="parent_test.done()">
+<h1>Fetching Tests From a Child Context</h1>
+<p>This test demonstrates the use of <tt>fetch_tests_from_window</tt> to pull
+tests from an <tt>iframe</tt> into the primary document.</p>
+<p>The test suite is expected to fail due to an unhandled exception in the
+child context.</p>
+<div id="log"></div>
+
+<iframe id="childContext" src="uncaught-exception-handle.html" style="display:none"></iframe>
+<!-- apisample4.html is a failing suite due to an unhandled Error. -->
+
+<script>
+  var childContext = document.getElementById("childContext");
+  fetch_tests_from_window(childContext.contentWindow);
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Error in remote: Error: Example Error"
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Test executing in parent context",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "This should show a harness status of 'Error' and a test status of 'Not Run'",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-tests.html b/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-tests.html
new file mode 100644
index 0000000000..246dddee11
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-tests.html
@@ -0,0 +1,85 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with iframe that consolidates tests via fetch_tests_from_window</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+var parent_test = async_test("Test executing in parent context");
+</script>
+</head>
+<body onload="parent_test.done()">
+<h1>Fetching Tests From a Child Context</h1>
+<p>This test demonstrates the use of <tt>fetch_tests_from_window</tt> to pull
+tests from an <tt>iframe</tt> into the primary document.</p>
+<p>The test suite will not complete until tests in the child context have finished
+executing</p>
+<div id="log"></div>
+
+<iframe id="childContext" src="promise-async.html" style="display:none"></iframe>
+
+<script>
+  var childContext = document.getElementById("childContext");
+  fetch_tests_from_window(childContext.contentWindow);
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Promise rejection",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promise resolution",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Promises and test assertion failures (should fail)",
+      "properties": {},
+      "message": "assert_true: This failure is expected expected true got false"
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promises are supported in your browser",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promises resolution chaining",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test executing in parent context",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Use of step_func with Promises",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Use of unreached_func with Promises (should fail)",
+      "properties": {},
+      "message": "assert_unreached: This failure is expected Reached unreachable code"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/iframe-msg.html b/testing/web-platform/tests/resources/test/tests/functional/iframe-msg.html
new file mode 100644
index 0000000000..283a5d98cc
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/iframe-msg.html
@@ -0,0 +1,84 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with iframe that notifies containing document via cross document messaging</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Notifications From Tests Running In An IFRAME</h1>
+<p>A test is run inside an <tt>iframe</tt> with a same origin document. The
+containing document should receive messages via <tt>postMessage</tt>/
+<tt>onmessage</tt> as the tests progress inside the <tt>iframe</tt>. A single
+passing test is expected in the summary below.
+</p>
+<div id="log"></div>
+
+<script>
+var t = async_test("Containing document receives messages");
+var start_received = false;
+var result_received = false;
+var completion_received = false;
+
+// These are the messages that are expected to be seen while running the tests
+// in the IFRAME.
+var expected_messages = [
+    t.step_func(
+        function(message) {
+            assert_equals(message.data.type, "start");
+            assert_own_property(message.data, "properties");
+        }),
+
+    t.step_func(
+        function(message) {
+            assert_equals(message.data.type, "test_state");
+            assert_equals(message.data.test.status, message.data.test.NOTRUN);
+        }),
+
+    t.step_func(
+        function(message) {
+            assert_equals(message.data.type, "result");
+            assert_equals(message.data.test.status, message.data.test.PASS);
+        }),
+
+    t.step_func(
+        function(message) {
+            assert_equals(message.data.type, "complete");
+            assert_equals(message.data.tests.length, 1);
+            assert_equals(message.data.tests[0].status,
+                          message.data.tests[0].PASS);
+            assert_equals(message.data.status.status, message.data.status.OK);
+            t.done();
+        }),
+
+    t.unreached_func("Too many messages received")
+];
+
+on_event(window,
+         "message",
+         function(message) {
+             var handler = expected_messages.shift();
+             handler(message);
+         });
+</script>
+<iframe src="single-page-test-pass.html" style="display:none">
+  <!-- single-page-test-pass.html implements a file_is_test test. -->
+</iframe>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Containing document receives messages",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/log-insertion.html b/testing/web-platform/tests/resources/test/tests/functional/log-insertion.html
new file mode 100644
index 0000000000..9a63c3dbde
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/log-insertion.html
@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<title>Log insertion</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function(t) {
+  assert_equals(document.body, null);
+}, "Log insertion before load");
+test(function(t) {
+  assert_equals(document.body, null);
+}, "Log insertion before load (again)");
+async_test(function(t) {
+  window.onload = t.step_func_done(function() {
+    var body = document.body;
+    assert_not_equals(body, null);
+
+    var log = document.getElementById("log");
+    assert_equals(log.parentNode, body);
+  });
+}, "Log insertion after load");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [{
+    "status_string": "PASS",
+    "name": "Log insertion before load",
+    "message": null,
+    "properties": {}
+  }, {
+    "status_string": "PASS",
+    "name": "Log insertion before load (again)",
+    "message": null,
+    "properties": {}
+  }, {
+    "status_string": "PASS",
+    "name": "Log insertion after load",
+    "message": null,
+    "properties": {}
+  }],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/no-title.html b/testing/web-platform/tests/resources/test/tests/functional/no-title.html
new file mode 100644
index 0000000000..a337e4e5f5
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/no-title.html
@@ -0,0 +1,146 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Tests with no title</title>
+</head>
+<script src="/resources/testharness.js"></script>
+
+<body>
+<h1>Tests with no title</h1>
+<div id="log"></div>
+<script>
+  test(function(){assert_true(true, '1')});
+  test(()=>assert_true(true, '2'));
+  test(() => assert_true(true, '3'));
+  test(() => assert_true(true, '3'));  // test duplicate behaviour
+  test(() => assert_true(true, '3'));  // test duplicate behaviour
+  test(() => {
+      assert_true(true, '4');
+  });
+  test(() => { assert_true(true, '5') });
+  test(() => { assert_true(true, '6') }   );
+  test(() => { assert_true(true, '7'); });
+  test(() => {});
+  test(() => { });
+  test(() => {;;;;});
+  test(() => { ; ; ; ; });
+  test(()=>{});
+  test(()=>{ });
+  test(()=>{;;;;});
+  test(()=>{ ; ; ; ; });
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '2')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '3')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '3') 1",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '3') 2",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 1",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '5')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '6')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "assert_true(true, '7')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 2",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 3",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 4",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 5",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 6",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 7",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 8",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Tests with no title 9",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/order.html b/testing/web-platform/tests/resources/test/tests/functional/order.html
new file mode 100644
index 0000000000..686383861a
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/order.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Ordering</title>
+<meta name="timeout" content="6000">
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(function() {}, 'second');
+test(function() {}, 'first');
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [{
+    "status_string": "PASS",
+    "name": "first",
+    "message": null,
+    "properties": {}
+  }, {
+    "status_string": "PASS",
+    "name": "second",
+    "message": null,
+    "properties": {}
+  }],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/promise-async.html b/testing/web-platform/tests/resources/test/tests/functional/promise-async.html
new file mode 100644
index 0000000000..fa82665cf0
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/promise-async.html
@@ -0,0 +1,172 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Async Tests and Promises</title>
+</head>
+<body>
+<h1>Async Tests and Promises</h1>
+<p>This test assumes ECMAScript 6 Promise support. Some failures are expected.</p>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+
+test(function() {
+  var p = new Promise(function(resolve, reject) {});
+  assert_true('then' in p);
+  assert_equals(typeof Promise.resolve, 'function');
+  assert_equals(typeof Promise.reject, 'function');
+}, "Promises are supported in your browser");
+
+(function() {
+  var t = async_test("Promise resolution");
+  t.step(function() {
+    Promise.resolve('x').then(
+      t.step_func(function(value) {
+        assert_equals(value, 'x');
+        t.done();
+      }),
+      t.unreached_func('Promise should not reject')
+    );
+  });
+}());
+
+(function() {
+  var t = async_test("Promise rejection");
+  t.step(function() {
+    Promise.reject(Error('fail')).then(
+      t.unreached_func('Promise should reject'),
+      t.step_func(function(reason) {
+        assert_true(reason instanceof Error);
+        assert_equals(reason.message, 'fail');
+        t.done();
+      })
+    );
+  });
+}());
+
+(function() {
+  var t = async_test("Promises resolution chaining");
+  t.step(function() {
+    var resolutions = [];
+    Promise.resolve('a').then(
+      t.step_func(function(value) {
+        resolutions.push(value);
+        return 'b';
+      })
+    ).then(
+      t.step_func(function(value) {
+        resolutions.push(value);
+        return 'c';
+      })
+    ).then(
+      t.step_func(function(value) {
+        resolutions.push(value);
+
+        assert_array_equals(resolutions, ['a', 'b', 'c']);
+        t.done();
+      })
+    ).catch(
+      t.unreached_func('promise should not have rejected')
+    );
+  });
+}());
+
+(function() {
+  var t = async_test("Use of step_func with Promises");
+  t.step(function() {
+    var resolutions = [];
+    Promise.resolve('x').then(
+      t.step_func_done(),
+      t.unreached_func('Promise should not have rejected')
+    );
+  });
+}());
+
+(function() {
+  var t = async_test("Promises and test assertion failures (should fail)");
+  t.step(function() {
+    var resolutions = [];
+    Promise.resolve('x').then(
+      t.step_func(function(value) {
+        assert_true(false, 'This failure is expected');
+      })
+    ).then(
+      t.unreached_func('Promise should not have resolved')
+    ).catch(
+      t.unreached_func('Promise should not have rejected')
+    );
+  });
+}());
+
+(function() {
+  var t = async_test("Use of unreached_func with Promises (should fail)");
+  t.step(function() {
+    var resolutions = [];
+    var r;
+    var p = new Promise(function(resolve, reject) {
+      // Reject instead of resolve, to demonstrate failure.
+      reject(123);
+    });
+    p.then(
+      function(value) {
+        assert_equals(value, 123, 'This should not actually happen');
+      },
+      t.unreached_func('This failure is expected')
+    );
+  });
+}());
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Promise rejection",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promise resolution",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Promises and test assertion failures (should fail)",
+      "properties": {},
+      "message": "assert_true: This failure is expected expected true got false"
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promises are supported in your browser",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promises resolution chaining",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Use of step_func with Promises",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Use of unreached_func with Promises (should fail)",
+      "properties": {},
+      "message": "assert_unreached: This failure is expected Reached unreachable code"
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/promise-with-sync.html b/testing/web-platform/tests/resources/test/tests/functional/promise-with-sync.html
new file mode 100644
index 0000000000..e8e680a9c7
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/promise-with-sync.html
@@ -0,0 +1,79 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Promise Tests and Synchronous Tests</title>
+</head>
+<body>
+<h1>Promise Tests</h1>
+<p>This test demonstrates the use of <tt>promise_test</tt> alongside synchronous tests.</p>
+<div id="log"></div>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+<script>
+"use strict";
+var sequence = [];
+
+test(function(t) {
+  assert_array_equals(sequence, []);
+  sequence.push(1);
+}, "first synchronous test");
+
+promise_test(function() {
+  assert_array_equals(sequence, [1, 2]);
+
+  return Promise.resolve()
+    .then(function() {
+        assert_array_equals(sequence, [1, 2]);
+        sequence.push(3);
+      });
+}, "first promise_test");;
+
+test(function(t) {
+  assert_array_equals(sequence, [1]);
+  sequence.push(2);
+}, "second synchronous test");
+
+promise_test(function() {
+  assert_array_equals(sequence, [1, 2, 3]);
+
+  return Promise.resolve()
+    .then(function() {
+        assert_array_equals(sequence, [1, 2, 3]);
+      });
+}, "second promise_test");;
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "message": null,
+      "properties": {},
+      "name": "first promise_test",
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "properties": {},
+      "name": "first synchronous test",
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "properties": {},
+      "name": "second promise_test",
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "properties": {},
+      "name": "second synchronous test",
+      "status_string": "PASS"
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/promise.html b/testing/web-platform/tests/resources/test/tests/functional/promise.html
new file mode 100644
index 0000000000..f35feb0e21
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/promise.html
@@ -0,0 +1,219 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Promise Tests</title>
+</head>
+<body>
+<h1>Promise Tests</h1>
+<p>This test demonstrates the use of <tt>promise_test</tt>. Assumes ECMAScript 6
+Promise support. Some failures are expected.</p>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+test(
+    function() {
+        var p = new Promise(function(resolve, reject){});
+        assert_true("then" in p);
+        assert_equals(typeof Promise.resolve, "function");
+        assert_equals(typeof Promise.reject, "function");
+    },
+    "Promises are supported in your browser");
+
+promise_test(
+    function() {
+        return Promise.resolve("x")
+            .then(
+                function(value) {
+                    assert_equals(value,
+                                  "x",
+                                  "Fulfilled promise should pass result to " +
+                                  "fulfill reaction.");
+                });
+    },
+    "Promise fulfillment with result");
+
+promise_test(
+    function(t) {
+        return Promise.reject(new Error("fail"))
+            .then(t.unreached_func("Promise should reject"),
+                function(reason) {
+                    assert_true(
+                        reason instanceof Error,
+                        "Rejected promise should pass reason to fulfill reaction.");
+                    assert_equals(
+                        reason.message,
+                        "fail",
+                        "Rejected promise should pass reason to reject reaction.");
+                });
+    },
+    "Promise rejection with result");
+
+promise_test(
+    function() {
+        var resolutions = [];
+        return Promise.resolve("a")
+            .then(
+                function(value) {
+                    resolutions.push(value);
+                    return "b";
+                })
+            .then(
+                function(value) {
+                    resolutions.push(value);
+                    return "c";
+                })
+            .then(
+                function(value) {
+                    resolutions.push(value);
+                    assert_array_equals(resolutions, ["a", "b", "c"]);
+                });
+    },
+    "Chain of promise resolutions");
+
+promise_test(
+    function(t) {
+        var resolutions = [];
+        return Promise.resolve("x")
+            .then(
+                function(value) {
+                    assert_true(false, "Expected failure.");
+                })
+            .then(t.unreached_func("UNEXPECTED FAILURE: Promise should not have resolved."));
+    },
+    "Assertion failure in a fulfill reaction (should FAIL with an expected failure)");
+
+promise_test(
+    function(t) {
+        return new Promise(
+                function(resolve, reject) {
+                    reject(123);
+                })
+            .then(t.unreached_func("UNEXPECTED FAILURE: Fulfill reaction reached after rejection."),
+                  t.unreached_func("Expected failure."));
+    },
+    "unreached_func as reactor (should FAIL with an expected failure)");
+
+promise_test(
+    function() {
+        return true;
+    },
+    "promise_test with function that doesn't return a Promise (should FAIL)");
+
+promise_test(function(){},
+             "promise_test with function that doesn't return anything");
+
+promise_test(
+    function() { return { then: 23 }; },
+    "promise_test that returns a non-thenable (should FAIL)");
+
+promise_test(
+    function() {
+        return Promise.reject("Expected rejection");
+    },
+    "promise_test with unhandled rejection (should FAIL)");
+
+promise_test(
+    function() {
+        return Promise.resolve(10)
+            .then(
+                function(value) {
+                    throw Error("Expected exception.");
+                });
+    },
+    "promise_test with unhandled exception in fulfill reaction (should FAIL)");
+
+promise_test(
+    function(t) {
+        return Promise.reject(10)
+            .then(
+                t.unreached_func("UNEXPECTED FAILURE: Fulfill reaction reached after rejection."),
+                function(value) {
+                    throw Error("Expected exception.");
+                });
+    },
+    "promise_test with unhandled exception in reject reaction (should FAIL)");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "FAIL",
+      "name": "Assertion failure in a fulfill reaction (should FAIL with an expected failure)",
+      "message": "assert_true: Expected failure. expected true got false",
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Chain of promise resolutions",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promise fulfillment with result",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promise rejection with result",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "PASS",
+      "name": "Promises are supported in your browser",
+      "message": null,
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test with function that doesn't return a Promise (should FAIL)",
+      "message": "promise_test: test body must return a 'thenable' object (received an object with no `then` method)",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test with function that doesn't return anything",
+      "message": "promise_test: test body must return a 'thenable' object (received undefined)",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test that returns a non-thenable (should FAIL)",
+      "message": "promise_test: test body must return a 'thenable' object (received an object with no `then` method)",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test with unhandled exception in fulfill reaction (should FAIL)",
+      "message": "promise_test: Unhandled rejection with value: object \"Error: Expected exception.\"",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test with unhandled exception in reject reaction (should FAIL)",
+      "message": "promise_test: Unhandled rejection with value: object \"Error: Expected exception.\"",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "promise_test with unhandled rejection (should FAIL)",
+      "message": "promise_test: Unhandled rejection with value: \"Expected rejection\"",
+      "properties": {}
+    },
+    {
+      "status_string": "FAIL",
+      "name": "unreached_func as reactor (should FAIL with an expected failure)",
+      "message": "assert_unreached: Expected failure. Reached unreachable code",
+      "properties": {}
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/queue.html b/testing/web-platform/tests/resources/test/tests/functional/queue.html
new file mode 100644
index 0000000000..0c721286ec
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/queue.html
@@ -0,0 +1,130 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test queuing synchronous tests</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+"use strict";
+var inInitialTurn = true;
+
+test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+}, "First synchronous test");
+
+test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+}, "Second synchronous test");
+
+async_test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+  t.done();
+}, "First async_test (run in parallel)");
+
+async_test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+  t.done();
+}, "Second async_test (run in parallel)");
+
+test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+}, "Third synchronous test");
+
+promise_test(function(t) {
+  assert_false(
+    inInitialTurn, "should not execute in the initial turn of the event loop"
+  );
+
+  return Promise.resolve();
+}, "promise_test");
+
+async_test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+  t.done();
+}, "Third async_test (run in parallel)");
+
+test(function(t) {
+  assert_true(
+    inInitialTurn, "should execute in the initial turn of the event loop"
+  );
+}, "Fourth synchronous test");
+
+inInitialTurn = false;
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "properties": {},
+      "name": "First async_test (run in parallel)",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "First synchronous test",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "Fourth synchronous test",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "Second async_test (run in parallel)",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "Second synchronous test",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "Third async_test (run in parallel)",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "Third synchronous test",
+      "status_string": "PASS",
+      "message": null
+    },
+    {
+      "properties": {},
+      "name": "promise_test",
+      "status_string": "PASS",
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/setup-function-worker.js b/testing/web-platform/tests/resources/test/tests/functional/setup-function-worker.js
new file mode 100644
index 0000000000..82c1456aa6
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/setup-function-worker.js
@@ -0,0 +1,14 @@
+importScripts("/resources/testharness.js");
+
+// Regression test for https://github.com/web-platform-tests/wpt/issues/27299,
+// where we broke the ability for a setup function in a worker to contain an
+// assertion (even a passing one).
+setup(function() {
+    assert_true(true, "True is true");
+});
+
+// We must define at least one test for the harness, though it is not what we
+// are testing here.
+test(function() {
+    assert_false(false, "False is false");
+}, 'Worker test');
diff --git a/testing/web-platform/tests/resources/test/tests/functional/setup-worker-service.html b/testing/web-platform/tests/resources/test/tests/functional/setup-worker-service.html
new file mode 100644
index 0000000000..9f24adac2d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/setup-worker-service.html
@@ -0,0 +1,86 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Setup function in a service worker</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Setup function in a service worker</h1>
+<p>This test assumes that the browser supports <a href="http://www.w3.org/TR/service-workers/">ServiceWorkers</a>.
+<div id="log"></div>
+
+<script>
+test(function(t) {
+    assert_true("serviceWorker" in navigator,
+                "navigator.serviceWorker exists");
+}, "Browser supports ServiceWorker");
+
+promise_test(function() {
+    // Since the service worker registration could be in an indeterminate
+    // state (due to, for example, a previous test run failing), we start by
+    // unregstering our service worker and then registering it again.
+    var scope = "service-worker-scope";
+    var worker_url = "setup-function-worker.js";
+
+    return navigator.serviceWorker.register(worker_url, {scope: scope})
+        .then(function(registration) {
+            return registration.unregister();
+        }).then(function() {
+            return navigator.serviceWorker.register(worker_url, {scope: scope});
+        }).then(function(registration) {
+            add_completion_callback(function() {
+                registration.unregister();
+            });
+
+            return new Promise(function(resolve) {
+                registration.addEventListener("updatefound", function() {
+                    resolve(registration.installing);
+                });
+            });
+        }).then(function(worker) {
+            fetch_tests_from_worker(worker);
+        });
+}, "Register ServiceWorker");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports ServiceWorker",
+      "properties": {},
+      "message": null
+    },
+    {
+      "message": null,
+      "name": "Register ServiceWorker",
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "name": "Worker test",
+      "properties": {},
+      "status_string": "PASS"
+    }
+  ],
+  "summarized_asserts": [
+    {
+      "assert_name": "assert_true",
+      "test": "Browser supports ServiceWorker",
+      "args": [
+        "true",
+        "\"navigator.serviceWorker exists\""
+      ],
+      "status": 0
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/single-page-test-fail.html b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-fail.html
new file mode 100644
index 0000000000..8bbd530c48
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-fail.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+<title>Example with file_is_test (should fail)</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({ single_test: true });
+onload = function() {
+  assert_true(false);
+  done();
+}
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "FAIL",
+      "name": "Example with file_is_test (should fail)",
+      "properties": {},
+      "message": "uncaught exception: Error: assert_true: expected true got false"
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-assertions.html b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-assertions.html
new file mode 100644
index 0000000000..9b39d2a02c
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-assertions.html
@@ -0,0 +1,25 @@
+<!DOCTYPE HTML>
+<title>Example single page test with no asserts</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({ single_test: true });
+done();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Example single page test with no asserts",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-body.html b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-body.html
new file mode 100644
index 0000000000..cb018f4dae
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-body.html
@@ -0,0 +1,26 @@
+<!DOCTYPE HTML>
+<title>Example single page test with no body</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({ single_test: true });
+assert_true(true);
+done();
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Example single page test with no body",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/single-page-test-pass.html b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-pass.html
new file mode 100644
index 0000000000..e143e22f3c
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/single-page-test-pass.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+<title>Example with file_is_test</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+setup({ single_test: true });
+onload = function() {
+  assert_true(true);
+  done();
+}
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Example with file_is_test",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/step_wait.html b/testing/web-platform/tests/resources/test/tests/functional/step_wait.html
new file mode 100644
index 0000000000..ae3442c759
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/step_wait.html
@@ -0,0 +1,57 @@
+<!doctype html>
+<title>Tests for step_wait</title>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<div id=log></div>
+<script>
+promise_test(async t => {
+  let x = 1;
+  Promise.resolve().then(() => ++x);
+  await t.step_wait(() => x === 1);
+  assert_equals(x, 2);
+}, "Basic step_wait() test");
+
+promise_test(async t => {
+  let cond = false;
+  let x = 0;
+  setTimeout(() => cond = true, 100);
+  await t.step_wait(() => {
+    ++x;
+    return cond;
+  });
+  assert_equals(x, 2);
+}, "step_wait() isn't invoked too often");
+
+promise_test(async t => {
+  await t.step_wait(); // Throws
+}, "step_wait() takes an argument");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_tests": [
+    {
+      "name": "Basic step_wait() test",
+      "message": null,
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "name": "step_wait() isn't invoked too often",
+      "message": null,
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "name": "step_wait() takes an argument",
+      "message": "cond is not a function",
+      "properties": {},
+      "status_string": "FAIL"
+    }
+  ],
+  "type": "complete",
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  }
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/step_wait_func.html b/testing/web-platform/tests/resources/test/tests/functional/step_wait_func.html
new file mode 100644
index 0000000000..9fed18a3e2
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/step_wait_func.html
@@ -0,0 +1,49 @@
+<!doctype html>
+<title>Tests for step_wait_func and step_wait_func_done</title>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<div id=log></div>
+<script>
+async_test(t => {
+  let x = 0;
+  let step_x = 0;
+  setTimeout(() => ++x, 100);
+  t.step_wait_func(() => {
+    ++step_x;
+    return x === 1;
+  }, () => {
+    assert_equals(step_x, 2);
+    t.done();
+  });
+}, "Basic step_wait_func() test");
+
+async_test(t => {
+  let x = 0;
+  setTimeout(() => ++x, 100);
+  t.step_wait_func_done(() => true, () => assert_equals(x, 0));
+}, "Basic step_wait_func_done() test");
+
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "message": null,
+    "status_string": "OK"
+  },
+  "summarized_tests": [
+    {
+      "properties": {},
+      "message": null,
+      "name": "Basic step_wait_func() test",
+      "status_string": "PASS"
+    },
+    {
+      "properties": {},
+      "message": null,
+      "name": "Basic step_wait_func_done() test",
+      "status_string": "PASS"
+    }
+  ],
+  "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-promise-test.html b/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-promise-test.html
new file mode 100644
index 0000000000..9d8e5c11cc
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-promise-test.html
@@ -0,0 +1,241 @@
+<!doctype html>
+<title>testharness.js - task scheduling</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+<script>
+var sameTask = null;
+var sameMicrotask = null;
+var expectedError = new Error('This error is expected');
+
+promise_test(function() {
+  return Promise.resolve()
+    .then(function() {
+        sameMirotask = true;
+        Promise.resolve().then(() => sameMicrotask = false);
+      });
+}, 'promise test without cleanup #1');
+
+promise_test(function() {
+  assert_false(sameMicrotask);
+
+  return Promise.resolve();
+}, 'sub-test with 0 cleanup functions executes in distinct microtask from a passing sub-test');
+
+promise_test(function() {
+  return Promise.resolve()
+    .then(function() {
+        sameMirotask = true;
+        Promise.resolve().then(() => sameMicrotask = false);
+        throw expectedError;
+      });
+}, 'failing promise test without cleanup #1');
+
+promise_test(function() {
+  assert_false(sameMicrotask);
+
+  return Promise.resolve();
+}, 'sub-test with 0 cleanup functions executes in distinct microtask from a failing sub-test');
+
+promise_test(function(t) {
+  t.add_cleanup(function() {});
+
+  return Promise.resolve()
+    .then(function() {
+        sameMirotask = true;
+        Promise.resolve().then(() => sameMicrotask = false);
+      });
+}, 'promise test with cleanup #1');
+
+promise_test(function() {
+  assert_false(sameMicrotask);
+
+  return Promise.resolve();
+}, 'sub-test with some cleanup functions executes in distinct microtask from a passing sub-test');
+
+promise_test(function(t) {
+  t.add_cleanup(function() {});
+
+  return Promise.resolve()
+    .then(function() {
+        sameMirotask = true;
+        Promise.resolve().then(() => sameMicrotask = false);
+        throw expectedError;
+      });
+}, 'failing promise test with cleanup #1');
+
+promise_test(function() {
+  assert_false(sameMicrotask);
+
+  return Promise.resolve();
+}, 'sub-test with some cleanup functions executes in distinct microtask from a failing sub-test');
+
+promise_test(function(t) {
+  return Promise.resolve()
+    .then(function() {
+        sameTask = true;
+        t.step_timeout(() => sameTask = false, 0);
+      });
+}, 'promise test without cleanup #2');
+
+promise_test(function() {
+  assert_true(sameTask);
+
+  return Promise.resolve();
+}, 'sub-test with 0 cleanup functions executes in the same task as a passing sub-test');
+
+promise_test(function(t) {
+  return Promise.resolve()
+    .then(function() {
+        sameTask = true;
+        t.step_timeout(() => sameTask = false, 0);
+        throw expectedError;
+      });
+}, 'failing promise test without cleanup #2');
+
+promise_test(function() {
+  assert_true(sameTask);
+
+  return Promise.resolve();
+}, 'sub-test with 0 cleanup functions executes in the same task as a failing sub-test');
+
+promise_test(function(t) {
+  t.add_cleanup(function() {});
+
+  return Promise.resolve()
+    .then(function() {
+        sameTask = true;
+        t.step_timeout(() => sameTask = false, 0);
+      });
+}, 'promise test with cleanup #2');
+
+promise_test(function() {
+  assert_true(sameTask);
+
+  return Promise.resolve();
+}, 'sub-test with some cleanup functions executes in the same task as a passing sub-test');
+
+promise_test(function(t) {
+  t.add_cleanup(function() {});
+
+  return Promise.resolve()
+    .then(function() {
+        sameTask = true;
+        t.step_timeout(() => sameTask = false, 0);
+        throw expectedError;
+      });
+}, 'failing promise test with cleanup #2');
+
+promise_test(function() {
+  assert_true(sameTask);
+
+  return Promise.resolve();
+}, 'sub-test with some cleanup functions executes in the same task as a failing sub-test');
+</script>
+
+<script type="text/json" id="expected">
+{
+    "summarized_status": {
+        "message": null,
+        "status_string": "OK"
+    },
+    "summarized_tests": [
+        {
+            "message": "promise_test: Unhandled rejection with value: object \"Error: This error is expected\"",
+            "name": "failing promise test with cleanup #1",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": "promise_test: Unhandled rejection with value: object \"Error: This error is expected\"",
+            "name": "failing promise test with cleanup #2",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": "promise_test: Unhandled rejection with value: object \"Error: This error is expected\"",
+            "name": "failing promise test without cleanup #1",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": "promise_test: Unhandled rejection with value: object \"Error: This error is expected\"",
+            "name": "failing promise test without cleanup #2",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": null,
+            "name": "promise test with cleanup #1",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "promise test with cleanup #2",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "promise test without cleanup #1",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "promise test without cleanup #2",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in distinct microtask from a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in distinct microtask from a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in the same task as a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in the same task as a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in distinct microtask from a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in distinct microtask from a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in the same task as a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in the same task as a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        }
+    ],
+    "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-test.html b/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-test.html
new file mode 100644
index 0000000000..035844448d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/task-scheduling-test.html
@@ -0,0 +1,141 @@
+<!doctype html>
+<title>testharness.js - task scheduling</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+<script>
+var sameMicrotask = null;
+var expectedError = new Error('This error is expected');
+
+// Derived from `immediate`
+// https://github.com/calvinmetcalf/immediate/blob/c353bd2106648cee1d525bfda22cfc4456e69c0e/lib/mutation.js
+function microTask(callback) {
+  var observer = new MutationObserver(callback);
+  var element = document.createTextNode('');
+  observer.observe(element, {
+    characterData: true
+  });
+
+  element.data = true;
+};
+
+async_test(function(t) {
+  var microtask_ran = false;
+
+  t.step_timeout(t.step_func(function() {
+    assert_true(microtask_ran, 'function registered as a microtask was executed before task');
+    t.done();
+  }), 0);
+
+  microTask(function() {
+    microtask_ran = true;
+  });
+}, 'precondition: microtask creation logic functions as expected');
+
+test(function() {
+  sameMicrotask = true;
+  microTask(function() { sameMicrotask = false; });
+}, 'synchronous test without cleanup');
+
+test(function() {
+  assert_true(sameMicrotask);
+}, 'sub-test with 0 cleanup functions executes in the same microtask as a passing sub-test');
+
+test(function() {
+  sameMicrotask = true;
+  microTask(function() { sameMicrotask = false; });
+  throw expectedError;
+}, 'failing synchronous test without cleanup');
+
+test(function() {
+  assert_true(sameMicrotask);
+}, 'sub-test with 0 cleanup functions executes in the same microtask as a failing sub-test');
+
+test(function(t) {
+  t.add_cleanup(function() {});
+
+  sameMicrotask = true;
+  microTask(function() { sameMicrotask = false; });
+}, 'synchronous test with cleanup');
+
+test(function() {
+  assert_true(sameMicrotask);
+}, 'sub-test with some cleanup functions executes in the same microtask as a passing sub-test');
+
+test(function(t) {
+  t.add_cleanup(function() {});
+
+  sameMicrotask = true;
+  microTask(function() { sameMicrotask = false; });
+  throw expectedError;
+}, 'failing synchronous test with cleanup');
+
+test(function() {
+  assert_true(sameMicrotask);
+}, 'sub-test with some cleanup functions executes in the same microtask as a failing sub-test');
+</script>
+
+<script type="text/json" id="expected">
+{
+    "summarized_status": {
+        "message": null,
+        "status_string": "OK"
+    },
+    "summarized_tests": [
+        {
+            "message": "This error is expected",
+            "name": "failing synchronous test with cleanup",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": "This error is expected",
+            "name": "failing synchronous test without cleanup",
+            "properties": {},
+            "status_string": "FAIL"
+        },
+        {
+            "message": null,
+            "name": "precondition: microtask creation logic functions as expected",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in the same microtask as a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with 0 cleanup functions executes in the same microtask as a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in the same microtask as a failing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "sub-test with some cleanup functions executes in the same microtask as a passing sub-test",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "synchronous test with cleanup",
+            "properties": {},
+            "status_string": "PASS"
+        },
+        {
+            "message": null,
+            "name": "synchronous test without cleanup",
+            "properties": {},
+            "status_string": "PASS"
+        }
+    ],
+    "type": "complete"
+}
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-handle.html b/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-handle.html
new file mode 100644
index 0000000000..764b0c4055
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-handle.html
@@ -0,0 +1,33 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Harness Handling Uncaught Exception</title>
+</head>
+<script src="/resources/testharness.js"></script>
+
+<body>
+<h1>Harness Handling Uncaught Exception</h1>
+<div id="log"></div>
+<script>
+var t = async_test("This should show a harness status of 'Error' and a test status of 'Not Run'");
+throw new Error("Example Error");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Error: Example Error"
+  },
+  "summarized_tests": [
+    {
+      "status_string": "NOTRUN",
+      "name": "This should show a harness status of 'Error' and a test status of 'Not Run'",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-ignore.html b/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-ignore.html
new file mode 100644
index 0000000000..6bd0ddbb0d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-ignore.html
@@ -0,0 +1,35 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Harness Ignoring Uncaught Exception</title>
+</head>
+<script src="/resources/testharness.js"></script>
+
+<body>
+<h1>Harness Ignoring Uncaught Exception</h1>
+<div id="log"></div>
+<script>
+setup({allow_uncaught_exception:true});
+var t = async_test("setup({allow_uncaught_exception:true}) should allow tests to pass even if there is an exception");
+onerror = t.step_func(function() {t.done()});
+throw new Error("Example Error");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "setup({allow_uncaught_exception:true}) should allow tests to pass even if there is an exception",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-allow.html b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-allow.html
new file mode 100644
index 0000000000..ba28d4914f
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-allow.html
@@ -0,0 +1,45 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Dedicated Worker Tests - Allowed Uncaught Exception</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Dedicated Web Worker Tests - Allowed Uncaught Exception</h1>
+<p>Demonstrates running <tt>testharness</tt> based tests inside a dedicated web worker.
+<p>The test harness is expected to pass despite an uncaught exception in a worker because that worker is configured to allow uncaught exceptions.</p>
+<div id="log"></div>
+
+<script>
+test(function(t) {
+        assert_true("Worker" in self, "Browser should support Workers");
+    },
+    "Browser supports Workers");
+
+fetch_tests_from_worker(new Worker("worker-uncaught-allow.js"));
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports Workers",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "onerror event is triggered",
+      "properties": {},
+      "message": null
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-single.html b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-single.html
new file mode 100644
index 0000000000..486e067114
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-single.html
@@ -0,0 +1,56 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Dedicated Worker Tests - Uncaught Exception in Single-Page Test</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Dedicated Web Worker Tests - Uncaught Exception in Single-Page Test</h1>
+<p>Demonstrates running <tt>testharness</tt> based tests inside a dedicated web worker.
+<p>The test harness is expected to pass despite an uncaught exception in a worker because that worker is a single-page test.</p>
+<div id="log"></div>
+
+<script>
+test(function(t) {
+        assert_true("Worker" in self, "Browser should support Workers");
+    },
+    "Browser supports Workers");
+
+fetch_tests_from_worker(new Worker("worker-uncaught-single.js"));
+
+test(function(t) {
+        assert_false(false, "False is false");
+    },
+    "Test running on main document.");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "OK",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports Workers",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test running on main document.",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "worker-uncaught-single",
+      "properties": {},
+      "message": "Error: This failure is expected."
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated.sub.html b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated.sub.html
new file mode 100644
index 0000000000..efd703c760
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-dedicated.sub.html
@@ -0,0 +1,88 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Dedicated Worker Tests</title>
+<script src="../../../testharness.js"></script>
+<script src="../../../testharnessreport.js"></script>
+</head>
+<body>
+<h1>Dedicated Web Worker Tests</h1>
+<p>Demonstrates running <tt>testharness</tt> based tests inside a dedicated web worker.
+<p>The test harness is expected to fail due to an uncaught exception in one worker.</p>
+<div id="log"></div>
+
+<script>
+test(function(t) {
+        assert_true("Worker" in self, "Browser should support Workers");
+    },
+    "Browser supports Workers");
+
+fetch_tests_from_worker(new Worker("worker.js"));
+
+fetch_tests_from_worker(new Worker("worker-error.js"));
+
+test(function(t) {
+        assert_false(false, "False is false");
+    },
+    "Test running on main document.");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "ERROR",
+    "message": "Error: This failure is expected."
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports Workers",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Test running on main document.",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Worker async_test that completes successfully",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Worker test that completes successfully",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "worker test that completes successfully before exception",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "Worker test that doesn't run ('NOT RUN')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Worker test that fails ('FAIL')",
+      "properties": {},
+      "message": "assert_true: Failing test expected true got false"
+    },
+    {
+      "status_string": "TIMEOUT",
+      "name": "Worker test that times out ('TIMEOUT')",
+      "properties": {},
+      "message": "Test timed out"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-error.js b/testing/web-platform/tests/resources/test/tests/functional/worker-error.js
new file mode 100644
index 0000000000..7b89602f04
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-error.js
@@ -0,0 +1,8 @@
+importScripts("/resources/testharness.js");
+
+// The following sub-test ensures that the worker is not interpreted as a
+// single-page test.  The subsequent uncaught exception should therefore be
+// interpreted as a harness error rather than a single-page test failure.
+test(function() {}, "worker test that completes successfully before exception");
+
+throw new Error("This failure is expected.");
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-service.html b/testing/web-platform/tests/resources/test/tests/functional/worker-service.html
new file mode 100644
index 0000000000..2e07746e62
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-service.html
@@ -0,0 +1,115 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with a service worker</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Service Worker Tests</h1>
+<p>Demonstrates running <tt>testharness</tt> based tests inside a service worker.
+<p>The test harness should time out due to one of the tests inside the worker timing out.
+<p>This test assumes that the browser supports <a href="http://www.w3.org/TR/service-workers/">ServiceWorkers</a>.
+<div id="log"></div>
+
+<script>
+test(
+    function(t) {
+        assert_true("serviceWorker" in navigator,
+                    "navigator.serviceWorker exists");
+    },
+    "Browser supports ServiceWorker");
+
+promise_test(
+    function() {
+        // Since the service worker registration could be in an indeterminate
+        // state (due to, for example, a previous test run failing), we start by
+        // unregstering our service worker and then registering it again.
+        var scope = "service-worker-scope";
+        var worker_url = "worker.js";
+
+        return navigator.serviceWorker.register(worker_url, {scope: scope})
+            .then(
+                function(registration) {
+                    return registration.unregister();
+                })
+            .then(
+                function() {
+                    return navigator.serviceWorker.register(worker_url, {scope: scope});
+                })
+            .then(
+                function(registration) {
+                    add_completion_callback(
+                        function() {
+                            registration.unregister();
+                        });
+
+                    return new Promise(
+                        function(resolve) {
+                            registration.addEventListener("updatefound",
+                                function() {
+                                    resolve(registration.installing);
+                                });
+                        });
+                })
+            .then(
+                function(worker) {
+                    fetch_tests_from_worker(worker);
+                });
+    },
+    "Register ServiceWorker");
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "TIMEOUT",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports ServiceWorker",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Register ServiceWorker",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Worker async_test that completes successfully",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "PASS",
+      "name": "Worker test that completes successfully",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "NOTRUN",
+      "name": "Worker test that doesn't run ('NOT RUN')",
+      "properties": {},
+      "message": null
+    },
+    {
+      "status_string": "FAIL",
+      "name": "Worker test that fails ('FAIL')",
+      "properties": {},
+      "message": "assert_true: Failing test expected true got false"
+    },
+    {
+      "status_string": "TIMEOUT",
+      "name": "Worker test that times out ('TIMEOUT')",
+      "properties": {},
+      "message": "Test timed out"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-shared.html b/testing/web-platform/tests/resources/test/tests/functional/worker-shared.html
new file mode 100644
index 0000000000..e26f17dec2
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-shared.html
@@ -0,0 +1,73 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Example with a shared worker</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<h1>Shared Web Worker Tests</h1>
+<p>Demonstrates running <tt>testharness</tt> based tests inside a shared worker.
+<p>The test harness should time out due to one of the tests in the worker timing out.
+<p>This test assumes that the browser supports <a href="http://www.w3.org/TR/workers/#shared-workers-and-the-sharedworker-interface">shared web workers</a>.
+<div id="log"></div>
+
+<script>
+test(
+    function(t) {
+        assert_true("SharedWorker" in self,
+                    "Browser should support SharedWorkers");
+    },
+    "Browser supports SharedWorkers");
+
+fetch_tests_from_worker(new SharedWorker("worker.js",
+                                         "My shared worker"));
+</script>
+<script type="text/json" id="expected">
+{
+  "summarized_status": {
+    "status_string": "TIMEOUT",
+    "message": null
+  },
+  "summarized_tests": [
+    {
+      "status_string": "PASS",
+      "name": "Browser supports SharedWorkers",
+      "properties": {},
+      "message": null
+    },
+    {
+      "message": null,
+      "name": "Worker async_test that completes successfully",
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "name": "Worker test that completes successfully",
+      "properties": {},
+      "status_string": "PASS"
+    },
+    {
+      "message": null,
+      "name": "Worker test that doesn't run ('NOT RUN')",
+      "properties": {},
+      "status_string": "NOTRUN"
+    },
+    {
+      "message": "assert_true: Failing test expected true got false",
+      "name": "Worker test that fails ('FAIL')",
+      "properties": {},
+      "status_string": "FAIL"
+    },
+    {
+      "message": "Test timed out",
+      "name": "Worker test that times out ('TIMEOUT')",
+      "properties": {},
+      "status_string": "TIMEOUT"
+    }
+  ],
+  "type": "complete"
+}
+</script>
+</body>
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-allow.js b/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-allow.js
new file mode 100644
index 0000000000..6925d59349
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-allow.js
@@ -0,0 +1,19 @@
+importScripts("/resources/testharness.js");
+
+setup({allow_uncaught_exception:true});
+
+async_test(function(t) {
+  onerror = function() {
+    // Further delay the test's completion to ensure that the worker's
+    // `onerror` handler does not influence results in the parent context.
+    setTimeout(function() {
+      t.done();
+    }, 0);
+  };
+
+  setTimeout(function() {
+    throw new Error("This error is expected.");
+  }, 0);
+}, 'onerror event is triggered');
+
+done();
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-single.js b/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-single.js
new file mode 100644
index 0000000000..c04542b2f5
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-single.js
@@ -0,0 +1,8 @@
+importScripts("/resources/testharness.js");
+
+setup({ single_test: true });
+
+// Because this script enables the `single_test` configuration option, it
+// should be interpreted as a single-page test, and the uncaught exception
+// should be reported as a test failure (harness status: OK).
+throw new Error("This failure is expected.");
diff --git a/testing/web-platform/tests/resources/test/tests/functional/worker.js b/testing/web-platform/tests/resources/test/tests/functional/worker.js
new file mode 100644
index 0000000000..a923bc2d89
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/worker.js
@@ -0,0 +1,34 @@
+importScripts("/resources/testharness.js");
+
+test(
+    function(test) {
+        assert_true(true, "True is true");
+    },
+    "Worker test that completes successfully");
+
+test(
+    function(test) {
+        assert_true(false, "Failing test");
+    },
+    "Worker test that fails ('FAIL')");
+
+async_test(
+    function(test) {
+        assert_true(true, "True is true");
+    },
+    "Worker test that times out ('TIMEOUT')");
+
+async_test("Worker test that doesn't run ('NOT RUN')");
+
+async_test(
+    function(test) {
+        self.setTimeout(
+            function() {
+                test.done();
+            },
+            0);
+    },
+    "Worker async_test that completes successfully");
+
+// An explicit done() is required for dedicated and shared web workers.
+done();
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlArray/is_json_type.html b/testing/web-platform/tests/resources/test/tests/unit/IdlArray/is_json_type.html
new file mode 100644
index 0000000000..18e83a8e89
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlArray/is_json_type.html
@@ -0,0 +1,192 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlArray.prototype.is_json_type()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("DOMString")));
+        assert_true(idl.is_json_type(typeFrom("ByteString")));
+        assert_true(idl.is_json_type(typeFrom("USVString")));
+        idl.add_untested_idls('enum BarEnum { "a", "b", "c" };');
+        assert_true(idl.is_json_type(typeFrom("BarEnum")));
+    }, 'should return true for all string types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("Error")));
+        assert_false(idl.is_json_type(typeFrom("DOMException")));
+    }, 'should return false for all exception types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("Int8Array")));
+        assert_false(idl.is_json_type(typeFrom("Int16Array")));
+        assert_false(idl.is_json_type(typeFrom("Int32Array")));
+        assert_false(idl.is_json_type(typeFrom("Uint8Array")));
+        assert_false(idl.is_json_type(typeFrom("Uint16Array")));
+        assert_false(idl.is_json_type(typeFrom("Uint32Array")));
+        assert_false(idl.is_json_type(typeFrom("Uint8ClampedArray")));
+        assert_false(idl.is_json_type(typeFrom("BigInt64Array")));
+        assert_false(idl.is_json_type(typeFrom("BigUint64Array")));
+        assert_false(idl.is_json_type(typeFrom("Float32Array")));
+        assert_false(idl.is_json_type(typeFrom("Float64Array")));
+        assert_false(idl.is_json_type(typeFrom("ArrayBuffer")));
+        assert_false(idl.is_json_type(typeFrom("DataView")));
+    }, 'should return false for all buffer source types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("boolean")));
+    }, 'should return true for boolean');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("byte")));
+        assert_true(idl.is_json_type(typeFrom("octet")));
+        assert_true(idl.is_json_type(typeFrom("short")));
+        assert_true(idl.is_json_type(typeFrom("unsigned short")));
+        assert_true(idl.is_json_type(typeFrom("long")));
+        assert_true(idl.is_json_type(typeFrom("unsigned long")));
+        assert_true(idl.is_json_type(typeFrom("long long")));
+        assert_true(idl.is_json_type(typeFrom("unsigned long long")));
+        assert_true(idl.is_json_type(typeFrom("float")));
+        assert_true(idl.is_json_type(typeFrom("unrestricted float")));
+        assert_true(idl.is_json_type(typeFrom("double")));
+        assert_true(idl.is_json_type(typeFrom("unrestricted double")));
+    }, 'should return true for all numeric types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("Promise<DOMString>")));
+    }, 'should return false for promises');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("sequence<DOMException>")));
+        assert_true(idl.is_json_type(typeFrom("sequence<DOMString>")));
+    }, 'should handle sequences according to their inner types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("FrozenArray<DOMException>")));
+        assert_true(idl.is_json_type(typeFrom("FrozenArray<DOMString>")));
+    }, 'should handle frozen arrays according to their inner types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("record<DOMString, DOMString>")));
+        assert_false(idl.is_json_type(typeFrom("record<DOMString, Error>")));
+    }, 'should handle records according to their inner types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("object")));
+    }, 'should return true for object type');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("any")));
+    }, 'should return false for any type');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('dictionary Foo { DOMString foo; }; dictionary Bar : Foo { DOMString bar; };');
+        assert_true(idl.is_json_type(typeFrom("Foo")));
+        assert_true(idl.is_json_type(typeFrom("Bar")));
+    }, 'should return true for dictionaries whose members are all JSON types');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('dictionary Foo { };');
+        assert_true(idl.is_json_type(typeFrom("Foo")));
+    }, 'should return true for dictionaries which have no members');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('dictionary FooBar { DOMString a; Error b; }; dictionary Baz : FooBar {};');
+        assert_false(idl.is_json_type(typeFrom("FooBar")));
+        assert_false(idl.is_json_type(typeFrom("Baz")));
+    }, 'should return false for dictionaries whose members are not all JSON types');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo { DOMString toJSON(); };');
+        assert_true(idl.is_json_type(typeFrom("Foo")));
+    }, 'should return true for interfaces which declare a toJSON operation');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo { DOMString toJSON(); }; interface Bar : Foo { };');
+        assert_true(idl.is_json_type(typeFrom("Bar")));
+    }, 'should return true for interfaces which inherit from an interface which declares a toJSON operation');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo { }; interface mixin Bar { DOMString toJSON(); }; Foo includes Bar;');
+        idl.merge_mixins();
+        assert_true(idl.is_json_type(typeFrom("Foo")));
+    }, 'should return true for interfaces which mixin an interface which declare a toJSON operation');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo { };');
+        assert_false(idl.is_json_type(typeFrom("Foo")));
+    }, 'should return false for interfaces which do not declare a toJSON operation');
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo { object toJSON(); };');
+        assert_true(idl.is_json_type(typeFrom("(Foo or DOMString)")));
+    }, 'should return true for union types whose member types are JSON types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typeFrom("(DataView or DOMString)")));
+    }, 'should return false for union types whose member types are not all JSON types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("DOMString?")));
+        assert_false(idl.is_json_type(typeFrom("DataView?")));
+    }, 'should consider the inner types of nullable types');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typeFrom("[XAttr] long")));
+        assert_false(idl.is_json_type(typeFrom("[XAttr] DataView")));
+    }, 'should consider the inner types of annotated types.');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_throws_js(Error, _ => idl.is_json_type(typeFrom("Foo")));
+    }, "should throw if it references a dictionary, enum or interface which wasn't added to the IdlArray");
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface Foo : Bar { };');
+        assert_throws_js(Error, _ => idl.is_json_type(typeFrom("Foo")));
+    }, "should throw for interfaces which inherit from another interface which wasn't added to the IdlArray");
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_true(idl.is_json_type(typedefFrom("typedef double DOMHighResTimeStamp;").idlType));
+    }, 'should return true for typedefs whose source type is a JSON type');
+
+    test(function() {
+        var idl = new IdlArray();
+        assert_false(idl.is_json_type(typedefFrom("typedef DataView DOMHighResTimeStamp;").idlType));
+    }, 'should return false for typedefs whose source type is not a JSON type');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/get_reverse_inheritance_stack.html b/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/get_reverse_inheritance_stack.html
new file mode 100644
index 0000000000..418bcdec92
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/get_reverse_inheritance_stack.html
@@ -0,0 +1,47 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlDictionary.prototype.get_reverse_inheritance_stack()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var stack = dictionaryFrom('dictionary A { };').get_reverse_inheritance_stack();
+        assert_array_equals(stack.map(d => d.name), ["A"]);
+    }, 'should return an array that includes itself.');
+
+    test(function() {
+        var d = dictionaryFrom('dictionary A : B { };');
+        assert_throws_js(Error, _ => d.get_reverse_inheritance_stack());
+    }, "should throw for dictionaries which inherit from another dictionary which wasn't added to the IdlArray");
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_idls('dictionary A : B { };');
+        idl.add_untested_idls('dictionary B : C { }; dictionary C { };');
+        var A = idl.members["A"];
+        assert_array_equals(A.get_reverse_inheritance_stack().map(d => d.name), ["C", "B", "A"]);
+    }, 'should return an array of dictionaries in order of inheritance, starting with the base dictionary');
+
+    test(function () {
+      let i = new IdlArray();
+      i.add_untested_idls('dictionary A : B {};');
+      i.assert_throws(new IdlHarnessError('A inherits B, but B is undefined.'), i => i.test());
+    }, 'A : B with B undeclared should throw IdlHarnessError');
+
+    test(function () {
+      let i = new IdlArray();
+      i.add_untested_idls('dictionary A : B {};');
+      i.add_untested_idls('interface B {};');
+      i.assert_throws(new IdlHarnessError('A inherits B, but A is not an interface.'), i => i.test());
+    }, 'dictionary A : B with B interface should throw IdlHarnessError');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/test_partial_dictionary.html b/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/test_partial_dictionary.html
new file mode 100644
index 0000000000..d6137f6895
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/test_partial_dictionary.html
@@ -0,0 +1,39 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <title>idlharness: partial dictionaries</title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+  <script src="../../../idl-helper.js"></script>
+</head>
+
+<body>
+<pre id='idl'>
+dictionary A {};
+partial dictionary A {
+  boolean B;
+};
+partial dictionary A {
+  boolean C;
+};
+</pre>
+
+<script>
+'use strict';
+
+test(() => {
+  let idlArray = new IdlArray();
+  idlArray.add_idls(document.getElementById('idl').textContent);
+  idlArray.test();
+
+  let members = idlArray.members["A"].members.map(m => m.name);
+  assert_array_equals(members, ["B", "C"], 'A should contain B, C');
+}, 'Partial dictionaries');
+</script>
+
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/constructors.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/constructors.html
new file mode 100644
index 0000000000..e9ee3f8680
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/constructors.html
@@ -0,0 +1,26 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.constructors()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+// [Constructor] extended attribute should not be supported:
+test(function() {
+    var i = interfaceFrom('[Constructor] interface A { };');
+    assert_equals(i.constructors().length, 0);
+}, 'Interface with Constructor extended attribute.');
+
+test(function() {
+    var i = interfaceFrom('interface A { constructor(); };');
+    assert_equals(i.constructors().length, 1);
+}, 'Interface with constructor method');
+
+test(function() {
+    var i = interfaceFrom('interface A { constructor(); constructor(any value); };');
+    assert_equals(i.constructors().length, 2);
+}, 'Interface with constructor overloads');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/default_to_json_operation.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/default_to_json_operation.html
new file mode 100644
index 0000000000..5ade7d0d28
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/default_to_json_operation.html
@@ -0,0 +1,114 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlDictionary.prototype.default_to_json_operation()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var map = interfaceFrom('interface A { [Default] object toJSON(); };').default_to_json_operation();
+        assert_equals(map.size, 0);
+    }, 'should return an empty map when there are no attributes');
+
+    test(function() {
+        var r = interfaceFrom('interface A { };').default_to_json_operation();
+        assert_equals(r, null);
+    }, 'should return null when there is no toJSON method');
+
+    test(function() {
+        var r = interfaceFrom('interface A { DOMString toJSON(); };').default_to_json_operation();
+        assert_equals(r, null);
+    }, 'should return null when there is a toJSON method but it does not have the [Default] extended attribute');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface A : B { DOMString toJSON(); };");
+        context.add_idls("interface B { [Default] object toJSON(); };");
+        var r = context.members.A.default_to_json_operation();
+        assert_equals(r, null);
+    }, 'should return null when there is a toJSON method but it does not have the [Default] extended attribute even if this extended attribute exists on inherited interfaces');
+
+    test(function() {
+        var map = interfaceFrom('interface A { [Default] object toJSON(); static attribute DOMString foo; };').default_to_json_operation();
+        assert_equals(map.size, 0);
+    }, 'should not include static attributes');
+
+    test(function() {
+        var map = interfaceFrom('interface A { [Default] object toJSON(); attribute Promise<DOMString> bar; };').default_to_json_operation();
+        assert_equals(map.size, 0);
+    }, 'should not include attributes which are not JSON types');
+
+    test(function() {
+        var map = interfaceFrom('interface A { [Default] object toJSON(); DOMString bar(); };').default_to_json_operation();
+        assert_equals(map.size, 0);
+    }, 'should not include operations');
+
+    test(function() {
+        var map = interfaceFrom('interface A { [Default] object toJSON(); attribute DOMString bar; };').default_to_json_operation();
+        assert_equals(map.size, 1);
+        assert_true(map.has("bar"));
+        assert_equals(map.get("bar").idlType, "DOMString");
+    }, 'should return a map whose key/value pair represent the identifier and IDL type of valid attributes');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface A : B { [Default] object toJSON(); attribute DOMString a; };");
+        context.add_idls("interface B { [Default] object toJSON(); attribute long b; };");
+        var map = context.members.A.default_to_json_operation();
+        assert_array_equals([...map.keys()], ["b", "a"]);
+        assert_array_equals([...map.values()].map(v => v.idlType), ["long", "DOMString"]);
+    }, 'should return a properly ordered map that contains IDL types of valid attributes for inherited interfaces');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface A : B { attribute DOMString a; };");
+        context.add_idls("interface B { [Default] object toJSON(); attribute long b; };");
+        var map = context.members.A.default_to_json_operation();
+        assert_equals(map.size, 1);
+        assert_true(map.has("b"));
+        assert_equals(map.get("b").idlType, "long");
+        assert_array_equals([...map.keys()], ["b"]);
+    }, 'should not include attributes of the current interface when the [Default] toJSON method in inherited');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface A : B { [Default] object toJSON(); };");
+        context.add_idls("interface B : C { [Default] object toJSON(); attribute DOMString foo; };");
+        context.add_idls("interface C { [Default] object toJSON(); attribute long foo; };");
+        var map = context.members.A.default_to_json_operation();
+        assert_equals(map.size, 1);
+        assert_true(map.has("foo"));
+        assert_equals(map.get("foo").idlType, "DOMString");
+    }, 'attributes declared further away in the inheritance hierarchy should be masked by attributes declared closer');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface A { [Default] object toJSON(); attribute DOMString a; };");
+        context.add_idls("interface B : A { attribute any b; };");
+        context.add_idls("interface C : B { [Default] object toJSON(); attribute long c; };");
+        var map = context.members.C.default_to_json_operation();
+        assert_array_equals([...map.keys()], ["a", "c"]);
+        assert_array_equals([...map.values()].map(v => v.idlType), ["DOMString", "long"]);
+    }, 'should return an ordered map that ignores attributes of inherited interfaces which do not declare a [Default] toJSON operation.');
+
+    test(function() {
+        var context = new IdlArray();
+        context.add_idls("interface D { attribute DOMString d; };");
+        context.add_idls("interface mixin M { [Default] object toJSON(); attribute long m; };");
+        context.add_idls("D includes M;");
+        context.merge_mixins();
+        var map = context.members.D.default_to_json_operation();
+        assert_array_equals([...map.keys()], ["d", "m"]);
+        assert_array_equals([...map.values()].map(v => v.idlType), ["DOMString", "long"]);
+    }, 'should return a properly ordered map that accounts for mixed-in interfaces which declare a [Default] toJSON operation.');
+</script>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/do_member_unscopable_asserts.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/do_member_unscopable_asserts.html
new file mode 100644
index 0000000000..90142efe6b
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/do_member_unscopable_asserts.html
@@ -0,0 +1,56 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlDictionary.prototype.do_member_unscopable_asserts()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    'use strict';
+    function mock_interface_A(unscopables) {
+        self.A = function A() {};
+        A.prototype[Symbol.unscopables] = unscopables;
+    }
+
+    test(function() {
+        const i = interfaceFrom('interface A { [Unscopable] attribute any x; };');
+        const member = i.members[0];
+        assert_true(member.isUnscopable);
+        mock_interface_A({ x: true });
+        i.do_member_unscopable_asserts(member);
+    }, 'should not throw for [Unscopable] with property in @@unscopables');
+
+    test(function() {
+        const i = interfaceFrom('interface A { [Unscopable] attribute any x; };');
+        const member = i.members[0];
+        assert_true(member.isUnscopable);
+        mock_interface_A({});
+        // assert_throws_* can't be used because they rethrow AssertionErrors.
+        try {
+            i.do_member_unscopable_asserts(member);
+        } catch(e) {
+            assert_true(e.message.includes('Symbol.unscopables'));
+            return;
+        }
+        assert_unreached('did not throw');
+    }, 'should throw for [Unscopable] with property missing from @@unscopables');
+
+    // This test checks that for attributes/methods which aren't [Unscopable]
+    // in the IDL, we don't assert that @@unscopables is missing the property.
+    // This could miss implementation bugs, but [Unscopable] is so rarely used
+    // that it's fairly unlikely to ever happen.
+    test(function() {
+        const i = interfaceFrom('interface A { attribute any x; };');
+        const member = i.members[0];
+        assert_false(member.isUnscopable);
+        mock_interface_A({ x: true });
+        i.do_member_unscopable_asserts(member);
+    }, 'should not throw if [Unscopable] is used but property is in @@unscopables');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object.html
new file mode 100644
index 0000000000..a3d901a752
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object.html
@@ -0,0 +1,22 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.get_interface_object()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+test(function() {
+    window.A = {};
+    var i = interfaceFrom('interface A { };');
+    assert_equals(i.get_interface_object(), window.A);
+}, 'Interface does not have LegacyNamespace.');
+
+test(function() {
+    window.Foo = { A: {} };
+    var i = interfaceFrom('[LegacyNamespace=Foo] interface A { }; namespace Foo { };');
+    assert_equals(i.get_interface_object(), window.Foo.A);
+}, 'Interface has LegacyNamespace');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object_owner.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object_owner.html
new file mode 100644
index 0000000000..51ab2067bc
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object_owner.html
@@ -0,0 +1,21 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.get_interface_object_owner()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+test(function() {
+    var i = interfaceFrom('interface A { };');
+    assert_equals(i.get_interface_object_owner(), window);
+}, 'Interface does not have LegacyNamespace.');
+
+test(function() {
+    window.Foo = {};
+    var i = interfaceFrom('[LegacyNamespace=Foo] interface A { }; namespace Foo { };');
+    assert_equals(i.get_interface_object_owner(), window.Foo);
+}, 'Interface has LegacyNamespace');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_legacy_namespace.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_legacy_namespace.html
new file mode 100644
index 0000000000..e2d42bb09e
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_legacy_namespace.html
@@ -0,0 +1,20 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.get_legacy_namespace()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+test(function() {
+    var i = interfaceFrom('interface A { };');
+    assert_equals(i.get_legacy_namespace(), undefined);
+}, 'Interface does not have LegacyNamespace.');
+
+test(function() {
+    var i = interfaceFrom('[LegacyNamespace=Foo] interface A { }; namespace Foo { };');
+    assert_equals(i.get_legacy_namespace(), "Foo");
+}, 'Interface has LegacyNamespace');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_qualified_name.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_qualified_name.html
new file mode 100644
index 0000000000..677a31b5e7
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_qualified_name.html
@@ -0,0 +1,20 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.get_qualified_name()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+test(function() {
+    var i = interfaceFrom('interface A { };');
+    assert_equals(i.get_qualified_name(), "A");
+}, 'Interface does not have LegacyNamespace.');
+
+test(function() {
+    var i = interfaceFrom('[LegacyNamespace=Foo] interface A { }; namespace Foo { };');
+    assert_equals(i.get_qualified_name(), "Foo.A");
+}, 'Interface has LegacyNamespace');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_reverse_inheritance_stack.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_reverse_inheritance_stack.html
new file mode 100644
index 0000000000..0c066baabb
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_reverse_inheritance_stack.html
@@ -0,0 +1,49 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlInterface.prototype.get_reverse_inheritance_stack()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var stack = interfaceFrom('interface A { };').get_reverse_inheritance_stack();
+        assert_array_equals(stack.map(i => i.name), ["A"]);
+    }, 'should return an array that includes itself.');
+
+    test(function() {
+        var i = interfaceFrom('interface A : B { };');
+        assert_throws_js(Error, _ => i.get_reverse_inheritance_stack());
+    }, "should throw for interfaces which inherit from another interface which wasn't added to the IdlArray");
+
+    test(function() {
+        var idl = new IdlArray();
+        idl.add_idls('interface A : B { };');
+        idl.add_untested_idls('interface B : C { }; interface C { };');
+        var A = idl.members["A"];
+        assert_array_equals(A.get_reverse_inheritance_stack().map(i => i.name), ["C", "B", "A"]);
+    }, 'should return an array of interfaces in order of inheritance, starting with the base interface');
+
+    test(function () {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface A : B { };');
+        idl.add_untested_idls('interface B : A { };');
+        idl.assert_throws('A has a circular dependency: A,B,A', i => i.test());
+    }, 'should throw when inheritance is circular');
+
+    test(function () {
+        var idl = new IdlArray();
+        idl.add_untested_idls('interface A : B { };');
+        idl.assert_throws(
+            'Duplicate identifier A',
+            i => i.add_untested_idls('interface A : C { };'));
+    }, 'should throw when multiple inheritances defined');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_default_to_json_regular_operation.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_default_to_json_regular_operation.html
new file mode 100644
index 0000000000..b47262b72b
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_default_to_json_regular_operation.html
@@ -0,0 +1,47 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlInterface.prototype.has_default_to_json_regular_operation()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var i = interfaceFrom('interface A { };');
+        assert_false(i.has_default_to_json_regular_operation());
+    }, 'should return false when the interface declares no toJSON operation.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { static object toJSON(); };');
+        assert_false(i.has_default_to_json_regular_operation());
+    }, 'should return false when the interface declares a static toJSON operation.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { object toJSON(); };');
+        assert_false(i.has_default_to_json_regular_operation());
+    }, 'should return false when the interface declares a regular toJSON operation with no extended attribute.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { [x] object toJSON(); };');
+        assert_false(i.has_default_to_json_regular_operation());
+    }, 'should return false when the interface declares a regular toJSON operation with another extented attribute.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { [Default] object toJSON(); };');
+        assert_true(i.has_default_to_json_regular_operation());
+    }, 'should return true when the interface declares a regular toJSON operation with the [Default] extented attribute.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { [Attr, AnotherAttr, Default] object toJSON(); };');
+        assert_true(i.has_default_to_json_regular_operation());
+    }, 'should return true when the interface declares a regular toJSON operation with multiple extended attributes, including [Default].');
+</script>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_to_json_regular_operation.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_to_json_regular_operation.html
new file mode 100644
index 0000000000..a1a641bd97
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_to_json_regular_operation.html
@@ -0,0 +1,31 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlInterface.prototype.has_to_json_regular_operation()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var i = interfaceFrom('interface A { };');
+        assert_false(i.has_to_json_regular_operation());
+    }, 'should return false when the interface declares no toJSON operation.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { static object toJSON(); };');
+        assert_false(i.has_to_json_regular_operation());
+    }, 'should return false when the interface declares a static toJSON operation.');
+
+    test(function() {
+        var i = interfaceFrom('interface A { object toJSON(); };');
+        assert_true(i.has_to_json_regular_operation());
+    }, 'should return true when the interface declares a regular toJSON operation.');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/should_have_interface_object.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/should_have_interface_object.html
new file mode 100644
index 0000000000..3ce945751d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/should_have_interface_object.html
@@ -0,0 +1,30 @@
+<!DOCTYPE HTML>
+<title>IdlInterface.prototype.should_have_interface_object()</title>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+test(function() {
+    var i = interfaceFrom("callback interface A { const unsigned short B = 0; };");
+    assert_true(i.should_have_interface_object());
+}, "callback interface with a constant");
+
+test(function() {
+    var i = interfaceFrom("callback interface A { undefined b(); sequence<any> c(); };");
+    assert_false(i.should_have_interface_object());
+}, "callback interface without a constant");
+
+test(function() {
+    var i = interfaceFrom("[LegacyNoInterfaceObject] interface A { };");
+    assert_false(i.should_have_interface_object());
+}, "non-callback interface with [LegacyNoInterfaceObject]");
+
+test(function() {
+    var i = interfaceFrom("interface A { };");
+    assert_true(i.should_have_interface_object());
+}, "non-callback interface without [LegacyNoInterfaceObject]");
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/test_primary_interface_of_undefined.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/test_primary_interface_of_undefined.html
new file mode 100644
index 0000000000..0031558ad4
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterface/test_primary_interface_of_undefined.html
@@ -0,0 +1,29 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <title>idlharness test_primary_interface_of_undefined</title>
+</head>
+
+<body>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/WebIDLParser.js"></script>
+  <script src="/resources/idlharness.js"></script>
+  <script>
+    'use strict';
+    test(function () {
+      let i = new IdlArray();
+      i.add_untested_idls('interface A : B {};');
+      i.assert_throws(new IdlHarnessError('A inherits B, but B is undefined.'), i => i.test());
+    }, 'A : B with B undeclared should throw IdlHarnessError');
+
+    test(function () {
+      let i = new IdlArray();
+      i.add_untested_idls('interface A : B {};');
+      i.add_untested_idls('dictionary B {};');
+      i.assert_throws(new IdlHarnessError('A inherits B, but B is not an interface.'), i => i.test());
+    }, 'interface A : B with B dictionary should throw IdlHarnessError');
+  </script>
+</body>
+
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/is_to_json_regular_operation.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/is_to_json_regular_operation.html
new file mode 100644
index 0000000000..b3f402dd08
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/is_to_json_regular_operation.html
@@ -0,0 +1,42 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlInterfaceMember.prototype.is_to_json_regular_operation()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        var m = memberFrom("readonly attribute DOMString foo");
+        assert_false(m.is_to_json_regular_operation());
+    }, 'should return false when member is an attribute.');
+
+    test(function() {
+        var m = memberFrom("static undefined foo()");
+        assert_false(m.is_to_json_regular_operation());
+    }, 'should return false when member is a static operation.');
+
+    test(function() {
+        var m = memberFrom("static object toJSON()");
+        assert_false(m.is_to_json_regular_operation());
+    }, 'should return false when member is a static toJSON operation.');
+
+    test(function() {
+        var m = memberFrom("object toJSON()");
+        assert_true(m.is_to_json_regular_operation());
+    }, 'should return true when member is a regular toJSON operation.');
+
+    test(function() {
+        var m = memberFrom("[Foo] object toJSON()");
+        assert_true(m.is_to_json_regular_operation());
+    }, 'should return true when member is a regular toJSON operation with extensible attributes.');
+</script>
+</body>
+</html>
+
diff --git a/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/toString.html b/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/toString.html
new file mode 100644
index 0000000000..054dbb1ccb
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/toString.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>IdlInterfaceMember.prototype.toString()</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script src="../../../idl-helper.js"></script>
+<script>
+"use strict";
+const tests = [
+    ["long x", "long"],
+    ["long? x", "long?"],
+    ["Promise<long> x", "Promise<long>"],
+    ["Promise<long?> x", "Promise<long?>"],
+    ["sequence<long> x", "sequence<long>"],
+    ["(long or DOMString) x", "(long or DOMString)"],
+    ["long x, boolean y", "long, boolean"],
+    ["long x, optional boolean y", "long, optional boolean"],
+    ["long... args", "long..."],
+    ["sequence<long>... args", "sequence<long>..."],
+    ["(long or DOMString)... args", "(long or DOMString)..."],
+];
+for (const [input, output] of tests) {
+    test(function() {
+        var m = memberFrom(`undefined foo(${input})`);
+        assert_equals(m.toString(), `foo(${output})`);
+    }, `toString for ${input}`);
+}
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/assert_implements.html b/testing/web-platform/tests/resources/test/tests/unit/assert_implements.html
new file mode 100644
index 0000000000..6e35f38502
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/assert_implements.html
@@ -0,0 +1,43 @@
+<!DOCTYPE HTML>
+<html lang="en">
+<meta charset="utf-8">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/test/tests/unit/helpers.js"></script>
+<title>assert_implements unittests</title>
+<script>
+'use strict';
+
+test(() => {
+  // All values in JS that are not falsy are truthy, so we just check some
+  // common cases here.
+  assert_implements(true, 'true is a truthy value');
+  assert_implements(5, 'positive integeter is a truthy value');
+  assert_implements(-5, 'negative integeter is a truthy value');
+  assert_implements('foo', 'non-empty string is a truthy value');
+}, 'truthy values');
+
+test_failure(() => {
+  assert_implements(false);
+}, 'false is a falsy value');
+
+test_failure(() => {
+  assert_implements(0);
+}, '0 is a falsy value');
+
+test_failure(() => {
+  assert_implements('');
+}, 'empty string is a falsy value');
+
+test_failure(() => {
+  assert_implements(null);
+}, 'null is a falsy value');
+
+test_failure(() => {
+  assert_implements(undefined);
+}, 'undefined is a falsy value');
+
+test_failure(() => {
+  assert_implements(NaN);
+}, 'NaN is a falsy value');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/assert_implements_optional.html b/testing/web-platform/tests/resources/test/tests/unit/assert_implements_optional.html
new file mode 100644
index 0000000000..4f23e203c5
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/assert_implements_optional.html
@@ -0,0 +1,43 @@
+<!DOCTYPE HTML>
+<html lang="en">
+<meta charset="utf-8">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/test/tests/unit/helpers.js"></script>
+<title>assert_implements_optional unittests</title>
+<script>
+'use strict';
+
+test(() => {
+  // All values in JS that are not falsy are truthy, so we just check some
+  // common cases here.
+  assert_implements_optional(true, 'true is a truthy value');
+  assert_implements_optional(5, 'positive integeter is a truthy value');
+  assert_implements_optional(-5, 'negative integeter is a truthy value');
+  assert_implements_optional('foo', 'non-empty string is a truthy value');
+}, 'truthy values');
+
+test_failure(() => {
+  assert_implements_optional(false);
+}, 'false is a falsy value');
+
+test_failure(() => {
+  assert_implements_optional(0);
+}, '0 is a falsy value');
+
+test_failure(() => {
+  assert_implements_optional('');
+}, 'empty string is a falsy value');
+
+test_failure(() => {
+  assert_implements_optional(null);
+}, 'null is a falsy value');
+
+test_failure(() => {
+  assert_implements_optional(undefined);
+}, 'undefined is a falsy value');
+
+test_failure(() => {
+  assert_implements_optional(NaN);
+}, 'NaN is a falsy value');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/assert_object_equals.html b/testing/web-platform/tests/resources/test/tests/unit/assert_object_equals.html
new file mode 100644
index 0000000000..313d77b977
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/assert_object_equals.html
@@ -0,0 +1,152 @@
+<!DOCTYPE HTML>
+<html lang="en">
+<meta charset="utf-8">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/test/tests/unit/helpers.js"></script>
+<title>Assertion functions</title>
+<script>
+'use strict';
+
+test(function() {
+  assert_object_equals({}, {});
+}, 'empty objects');
+
+test(function() {
+  var actual = {};
+  var expected = {};
+  actual.a = actual;
+  expected.a = actual;
+
+  assert_object_equals(actual, expected);
+}, 'tolerates cycles in actual value');
+
+test(function() {
+  var actual = {};
+  var expected = {};
+  actual.a = expected;
+  expected.a = expected;
+
+  assert_object_equals(actual, expected);
+}, 'tolerates cycles in expected value');
+
+test(function() {
+  assert_object_equals({2: 99, 0: 23, 1: 45}, [23, 45, 99]);
+}, 'recognizes equivalence of actual object and expected array');
+
+test(function() {
+  assert_object_equals([23, 45, 99], {2: 99, 0: 23, 1: 45});
+}, 'recognizes equivalence of actual array and expected object');
+
+test(function() {
+  var actual = {};
+  var expected = {};
+  Object.defineProperty(actual, 'a', { value: 1, enumerable: false });
+
+  assert_not_equals(actual.a, expected.a);
+  assert_object_equals(actual, expected);
+}, 'non-enumerable properties in actual value ignored');
+
+test(function() {
+  var actual = {};
+  var expected = {};
+  Object.defineProperty(expected, 'a', { value: 1, enumerable: false });
+
+  assert_not_equals(actual.a, expected.a);
+  assert_object_equals(actual, expected);
+}, 'non-enumerable properties in expected value ignored');
+
+test(function() {
+  assert_object_equals({c: 3, a: 1, b: 2}, {a: 1, b: 2, c: 3});
+}, 'equivalent objects - "flat" object');
+
+test(function() {
+  assert_object_equals(
+    {c: {e: 5, d: 4}, b: 2, a: 1},
+    {a: 1, b: 2, c: {d: 4, e: 5}}
+  );
+}, 'equivalent objects - nested object');
+
+test(function() {
+  assert_object_equals(
+    {c: [4, 5], b: 2, a: 1},
+    {a: 1, b: 2, c: [4, 5]}
+  );
+}, 'equivalent objects - nested array');
+
+test(function() {
+  assert_object_equals({a: NaN}, {a: NaN});
+}, 'equivalent objects - NaN value');
+
+test(function() {
+  assert_object_equals({a: -0}, {a: -0});
+}, 'equivalent objects - negative zero value');
+
+test_failure(function() {
+  assert_object_equals(undefined, {});
+}, 'invalid actual value: undefined');
+
+test_failure(function() {
+  assert_object_equals(null, {});
+}, 'invalid actual value: null');
+
+test_failure(function() {
+  assert_object_equals(34, {});
+}, 'invalid actual value: number');
+
+test_failure(function() {
+  assert_object_equals({c: 3, a: 1, b: 2}, {a: 1, b: 1, c: 3});
+}, 'unequal property value - "flat" object');
+
+test_failure(function() {
+  var actual = Object.create({a: undefined});
+  var expected = {};
+
+  assert_object_equals(actual, expected);
+}, 'non-own properties in actual value verified');
+
+test_failure(function() {
+  var actual = {};
+  var expected = Object.create({a: undefined});
+
+  assert_object_equals(actual, expected);
+}, 'non-own properties in expected value verified');
+
+test_failure(function() {
+  assert_object_equals(
+    {a: 1, b: 2, c: {d: 5, e: 5, f: 6}},
+    {a: 1, b: 2, c: {d: 5, e: 7, f: 6}}
+  );
+}, 'unequal property value - nested object');
+
+test_failure(function() {
+  assert_object_equals(
+    {a: 1, b: 2, c: [4, 5, 6]},
+    {a: 1, b: 2, c: [4, 7, 6]}
+  );
+}, 'unequal property value - nested array');
+
+test_failure(function() {
+  assert_object_equals({a: NaN}, {a: 0});
+}, 'equivalent objects - NaN actual value');
+
+test_failure(function() {
+  assert_object_equals({a: 0}, {a: NaN});
+}, 'equivalent objects - NaN expected value');
+
+test_failure(function() {
+  assert_object_equals({a: -0}, {a: 0});
+}, 'equivalent objects - negative zero actual value');
+
+test_failure(function() {
+  assert_object_equals({a: 0}, {a: -0});
+}, 'equivalent objects - negative zero expected value');
+
+test_failure(function() {
+  assert_object_equals({a: 1}, {});
+}, 'actual contains additional property');
+
+test_failure(function() {
+  assert_object_equals({}, {a: 1});
+}, 'expected contains additional property');
+</script>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/async-test-return-restrictions.html b/testing/web-platform/tests/resources/test/tests/unit/async-test-return-restrictions.html
new file mode 100644
index 0000000000..0fde2e2422
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/async-test-return-restrictions.html
@@ -0,0 +1,135 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="/resources/testharness.js"></script>
+  <title>Restrictions on return value from `async_test`</title>
+</head>
+<body>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: {
+        status: getEnumProp(status, status.status),
+        message: status.message
+      },
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        async_test((t) => {t.done(); return undefined;}, 'before');
+        async_test((t) => {t.done(); return null;}, 'null');
+        async_test((t) => {t.done(); return undefined;}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "null" passed a function to `async_test` that returned a value.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.null, 'PASS');
+      // This test did not get the chance to start.
+      assert_equals(tests.after, undefined);
+    });
+}, 'test returning `null`');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        async_test((t) => {t.done(); return undefined;}, 'before');
+        async_test((t) => {t.done(); return {};}, 'object');
+        async_test((t) => {t.done(); return undefined;}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "object" passed a function to `async_test` that returned a value.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.object, 'PASS');
+      // This test did not get the chance to start.
+      assert_equals(tests.after, undefined);
+    });
+}, 'test returning an ordinary object');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        async_test((t) => {t.done(); return undefined;}, 'before');
+        async_test((t) => {t.done(); return Promise.resolve(5);}, 'thenable');
+        async_test((t) => {t.done(); return undefined;}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "thenable" passed a function to `async_test` that returned a value. ' +
+        'Consider using `promise_test` instead when using Promises or async/await.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.thenable, 'PASS');
+      // This test did not get a chance to start.
+      assert_equals(tests.after, undefined);
+    });
+}, 'test returning a thenable object');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/basic.html b/testing/web-platform/tests/resources/test/tests/unit/basic.html
new file mode 100644
index 0000000000..d52082f2e0
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/basic.html
@@ -0,0 +1,48 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>idlharness basic</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="/resources/idlharness.js"></script>
+<script>
+    "use strict";
+    test(function() {
+        assert_true("IdlArray" in window);
+    }, 'IdlArray constructor should be a global object');
+    test(function() {
+        assert_true(new IdlArray() instanceof IdlArray);
+    }, 'IdlArray constructor should be constructible');
+    test(function() {
+        assert_true("WebIDL2" in window);
+    }, 'WebIDL2 namespace should be a global object');
+    test(function() {
+        assert_equals(typeof WebIDL2.parse, "function");
+    }, 'WebIDL2 namespace should have a parse method');
+    test(function() {
+        try {
+            WebIDL2.parse("I'm a syntax error");
+            throw new Error("Web IDL didn't throw");
+        } catch (e) {
+            assert_equals(e.name, "WebIDLParseError");
+        }
+    }, 'WebIDL2 parse method should bail on incorrect WebIDL');
+    test(function() {
+        assert_equals(typeof WebIDL2.parse("interface Foo {};"), "object");
+    }, 'WebIDL2 parse method should produce an AST for correct WebIDL');
+    test(function () {
+        try {
+            let i = new IdlArray();
+            i.add_untested_idls(`interface C {};`);
+            i.assert_throws('Anything', i => i.test());
+        } catch (e) {
+            assert_true(e instanceof IdlHarnessError);
+        }
+    }, `assert_throws should throw if no IdlHarnessError thrown`);
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases-timeouts.html b/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases-timeouts.html
new file mode 100644
index 0000000000..760ac7154f
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases-timeouts.html
@@ -0,0 +1,120 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="timeout" content="long">
+  <script src="/resources/testharness.js"></script>
+  <title>Exceptional cases - timeouts</title>
+</head>
+<body>
+<p>
+  The tests in this file are executed in parallel to avoid exceeding the "long"
+  timeout duration.
+</p>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: getEnumProp(status, status.status),
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+(() => {
+  window.asyncTestCleanupCount1 = 0;
+  const nestedTest = makeTest(
+    () => {
+      async_test((t) => {
+        t.add_cleanup(() => window.parent.asyncTestCleanupCount1 += 1);
+        setTimeout(() => {
+          throw new Error('this error is expected');
+        });
+      }, 'test');
+    }
+  );
+  promise_test(() => {
+    return nestedTest.then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.test, 'TIMEOUT');
+        assert_equals(window.asyncTestCleanupCount1, 1);
+      });
+  }, 'uncaught exception during async_test which times out');
+})();
+
+(() => {
+  window.promiseTestCleanupCount2 = 0;
+  const nestedTest = makeTest(
+    () => {
+      promise_test((t) => {
+        t.add_cleanup(() => window.parent.promiseTestCleanupCount2 += 1);
+        setTimeout(() => {
+          throw new Error('this error is expected');
+        });
+
+        return new Promise(() => {});
+      }, 'test');
+    }
+  );
+  promise_test(() => {
+    return nestedTest.then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.test, 'TIMEOUT');
+        assert_equals(window.promiseTestCleanupCount2, 1);
+      });
+  }, 'uncaught exception during promise_test which times out');
+})();
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases.html b/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases.html
new file mode 100644
index 0000000000..4054d0311d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/exceptional-cases.html
@@ -0,0 +1,392 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="timeout" content="long">
+  <script src="/resources/testharness.js"></script>
+  <title>Exceptional cases</title>
+</head>
+<body>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: getEnumProp(status, status.status),
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+promise_test(() => {
+  return makeTest(
+      () => { done(); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_array_equals(Object.keys(tests), []);
+    });
+}, 'completion signaled before testing begins');
+
+promise_test(() => {
+  return makeTest(
+      () => { assert_true(true); done(); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_array_equals(Object.keys(tests), []);
+    });
+}, 'passing assertion before testing begins');
+
+promise_test(() => {
+  return makeTest(
+      () => { assert_false(true); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_array_equals(Object.keys(tests), []);
+    });
+}, 'failing assertion before testing begins');
+
+promise_test(() => {
+  return makeTest(
+      () => { throw new Error('this error is expected'); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_array_equals(Object.keys(tests), []);
+    });
+}, 'uncaught exception before testing begins');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ allow_uncaught_exception: true });
+        throw new Error('this error is expected');
+      },
+      () => {
+        test(function() {}, 'a');
+        test(function() {}, 'b');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.a, 'PASS');
+      assert_equals(tests.b, 'PASS');
+    });
+}, 'uncaught exception with subsequent subtest');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        async_test((t) => {
+          setTimeout(() => {
+            setTimeout(() => t.done(), 0);
+            async_test((t) => { setTimeout(t.done.bind(t), 0); }, 'after');
+            throw new Error('this error is expected');
+          }, 0);
+        }, 'during');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.during, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'uncaught exception during async_test');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        promise_test(() => {
+          return new Promise((resolve) => {
+            setTimeout(() => {
+              resolve();
+              promise_test(() => Promise.resolve(), 'after');
+              throw new Error('this error is expected');
+            }, 0);
+          });
+        }, 'during');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.during, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'uncaught exception during promise_test');
+
+promise_test(() => {
+  return makeTest(
+      () => { test(() => {}, 'before'); },
+      () => { throw new Error('this error is expected'); },
+      () => { test(() => {}, 'after'); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'uncaught exception between tests');
+
+promise_test(() => {
+  return makeTest(
+      () => { promise_test(() => Promise.resolve(), 'before'); },
+      () => { throw new Error('this error is expected'); },
+      () => { promise_test(() => Promise.resolve(), 'after'); }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'uncaught exception between promise_tests');
+
+
+// This feature of testharness.js is only observable in browsers which
+// implement the `unhandledrejection` event.
+if ('onunhandledrejection' in window) {
+
+  promise_test(() => {
+    return makeTest(
+        () => { Promise.reject(new Error('this error is expected')); }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_array_equals(Object.keys(tests), []);
+      });
+  }, 'unhandled rejection before testing begins');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          async_test((t) => {
+            Promise.reject(new Error('this error is expected'));
+
+            window.addEventListener('unhandledrejection', () => {
+            setTimeout(() => t.done(), 0);
+              async_test((t) => { setTimeout(t.done.bind(t), 0); }, 'after');
+              t.done();
+            });
+          }, 'during');
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.during, 'PASS');
+        assert_equals(tests.after, 'PASS');
+      });
+  }, 'unhandled rejection during async_test');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          promise_test(() => {
+            return new Promise((resolve) => {
+              Promise.reject(new Error('this error is expected'));
+
+              window.addEventListener('unhandledrejection', () => {
+                resolve();
+                promise_test(() => Promise.resolve(), 'after');
+                throw new Error('this error is expected');
+              }, 0);
+            });
+          }, 'during');
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.during, 'PASS');
+        assert_equals(tests.after, 'PASS');
+      });
+  }, 'unhandled rejection during promise_test');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          setup({ explicit_done: true });
+          test(() => {}, 'before');
+          Promise.reject(new Error('this error is expected'));
+          window.addEventListener('unhandledrejection', () => {
+            test(() => {}, 'after');
+            done();
+          });
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.before, 'PASS');
+        assert_true('after' in tests);
+      });
+  }, 'unhandled rejection between tests');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          setup({ explicit_done: true });
+          async_test((t) => { setTimeout(t.done.bind(t), 0); }, 'before');
+          Promise.reject(new Error('this error is expected'));
+          window.addEventListener('unhandledrejection', () => {
+            async_test((t) => { setTimeout(t.done.bind(t), 0); }, 'after');
+            done();
+          });
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.before, 'PASS');
+        assert_equals(tests.after, 'PASS');
+      });
+  }, 'unhandled rejection between async_tests');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          setup({ explicit_done: true });
+          promise_test(() => Promise.resolve(), 'before');
+          Promise.reject(new Error('this error is expected'));
+          window.addEventListener('unhandledrejection', () => {
+            promise_test(() => Promise.resolve(), 'after');
+            done();
+          });
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.before, 'PASS');
+        assert_true('after' in tests);
+      });
+  }, 'unhandled rejection between promise_tests');
+
+  promise_test(() => {
+    return makeTest(
+        () => {
+          test((t) => {
+            t.add_cleanup(() => { throw new Error('this error is expected'); });
+          }, 'during');
+          test((t) => {}, 'after');
+        }
+      ).then(({harness, tests}) => {
+        assert_equals(harness, 'ERROR');
+        assert_equals(tests.during, 'PASS');
+        assert_equals(tests.after, 'NOTRUN');
+      });
+  }, 'exception in `add_cleanup` of a test');
+
+}
+
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({explicit_done: true});
+        window.addEventListener('DOMContentLoaded', () => {
+          async_test((t) => {
+            t.add_cleanup(() => {
+              setTimeout(() => {
+                async_test((t) => t.done(), 'after');
+                done();
+              }, 0);
+              throw new Error('this error is expected');
+            });
+            setTimeout(t.done.bind(t), 0);
+          }, 'during');
+        });
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.during, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'exception in `add_cleanup` of an async_test');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        promise_test((t) => {
+          t.add_cleanup(() => { throw new Error('this error is expected'); });
+          return Promise.resolve();
+        }, 'test');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.test, 'PASS');
+    });
+}, 'exception in `add_cleanup` of a promise_test');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        promise_test((t) => {
+          t.step(() => {
+            throw new Error('this error is expected');
+          });
+        }, 'test');
+        async_test((t) => t.done(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.test, 'FAIL');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'exception in `step` of an async_test');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        promise_test((t) => {
+          t.step(() => {
+            throw new Error('this error is expected');
+          });
+
+          return new Promise(() => {});
+        }, 'test');
+
+        // This following test should be run to completion despite the fact
+        // that the promise returned by the previous test never resolves.
+        promise_test((t) => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.test, 'FAIL');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'exception in `step` of a promise_test');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/format-value.html b/testing/web-platform/tests/resources/test/tests/unit/format-value.html
new file mode 100644
index 0000000000..13d01b81f3
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/format-value.html
@@ -0,0 +1,123 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>format_value utility function</title>
+  <meta charset="utf-8">
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+"use strict";
+
+test(function() {
+  assert_equals(format_value(null), "null");
+}, "null");
+
+test(function() {
+  assert_equals(format_value(undefined), "undefined");
+}, "undefined");
+
+test(function() {
+  assert_equals(format_value(true), "true");
+  assert_equals(format_value(false), "false");
+}, "boolean values");
+
+test(function() {
+  assert_equals(format_value(0.4), "0.4");
+  assert_equals(format_value(0), "0");
+  assert_equals(format_value(-0), "-0");
+}, "number values");
+
+test(function() {
+  assert_equals(format_value("a string"), "\"a string\"");
+  assert_equals(format_value("new\nline"), "\"new\\nline\"");
+}, "string values");
+
+test(function() {
+  var node = document.createElement("span");
+  node.setAttribute("data-foo", "bar");
+  assert_true(
+    /<span\b/i.test(format_value(node)), "element includes tag name"
+  );
+  assert_true(
+    /data-foo=["']?bar["']?/i.test(format_value(node)),
+    "element includes attributes"
+  );
+}, "node value: element node");
+
+test(function() {
+  var text = document.createTextNode("wpt");
+  assert_equals(format_value(text), "Text node \"wpt\"");
+}, "node value: text node");
+
+test(function() {
+  var node = document.createProcessingInstruction("wpt1", "wpt2");
+  assert_equals(
+    format_value(node),
+    "ProcessingInstruction node with target \"wpt1\" and data \"wpt2\""
+  );
+}, "node value: ProcessingInstruction node");
+
+test(function() {
+  var node = document.createComment("wpt");
+  assert_equals(format_value(node), "Comment node <!--wpt-->");
+}, "node value: comment node");
+
+test(function() {
+  var node = document.implementation.createDocument(
+    "application/xhtml+xml", "", null
+  );
+
+  assert_equals(format_value(node), "Document node with 0 children");
+
+  node.appendChild(document.createElement('html'));
+
+  assert_equals(format_value(node), "Document node with 1 child");
+}, "node value: document node");
+
+test(function() {
+  var node = document.implementation.createDocumentType("foo", "baz", "baz");
+
+  assert_equals(format_value(node), "DocumentType node");
+}, "node value: DocumentType node");
+
+test(function() {
+  var node = document.createDocumentFragment();
+
+  assert_equals(format_value(node), "DocumentFragment node with 0 children");
+
+  node.appendChild(document.createElement("span"));
+
+  assert_equals(format_value(node), "DocumentFragment node with 1 child");
+
+  node.appendChild(document.createElement("span"));
+
+  assert_equals(format_value(node), "DocumentFragment node with 2 children");
+}, "node value: DocumentFragment node");
+
+test(function() {
+  assert_equals(format_value(Symbol("wpt")), "symbol \"Symbol(wpt)\"");
+}, "symbol value");
+
+test(function() {
+ assert_equals(format_value([]), "[]");
+ assert_equals(format_value(["one"]), "[\"one\"]");
+ assert_equals(format_value(["one", "two"]), "[\"one\", \"two\"]");
+}, "array values");
+
+test(function() {
+  var obj = {
+    toString: function() {
+      throw "wpt";
+    }
+  };
+
+  assert_equals(
+    format_value(obj), "[stringifying object threw wpt with type string]"
+  );
+}, "object value with faulty `toString`");
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/helpers.js b/testing/web-platform/tests/resources/test/tests/unit/helpers.js
new file mode 100644
index 0000000000..ca378a27c9
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/helpers.js
@@ -0,0 +1,21 @@
+// Helper for testing assertion failure cases for a testharness.js API
+//
+// The `assert_throws_*` functions cannot be used for this purpose because they
+// always fail in response to AssertionError exceptions, even when this is
+// expressed as the expected error.
+function test_failure(fn, name) {
+  test(function() {
+    try {
+      fn();
+    } catch (err) {
+      if (err instanceof AssertionError) {
+        return;
+      }
+      throw new AssertionError('Expected an AssertionError, but' + err);
+    }
+    throw new AssertionError(
+      'Expected an AssertionError, but no error was thrown'
+    );
+  }, name);
+}
+
diff --git a/testing/web-platform/tests/resources/test/tests/unit/late-test.html b/testing/web-platform/tests/resources/test/tests/unit/late-test.html
new file mode 100644
index 0000000000..693d7e3c81
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/late-test.html
@@ -0,0 +1,54 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Test declared after harness completion</title>
+</head>
+<body>
+<div id="log"></div>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<p>This test simulates an automated test running scenario, where the test
+results emitted by testharness.js may be interpreted after some delay. It is
+intended to demonstrate that in such cases, any additional tests which are
+executed during that delay are <em>not</em> included in the dataset.</p>
+
+<p>Although these "late" tests are likely an indication of a mistake in test
+design, they cannot be detected deterministically, so in the interest of
+stability, they should be silently tolerated.</p>
+<script>
+async_test(function(t) {
+    var source = [
+        "<div id='log'></div>",
+        "<script src='/resources/testharness.js'></" + "script>",
+        "<script src='/resources/testharnessreport.js'></" + "script>",
+        "<script>",
+        "parent.childReady(window);",
+        "setup({ explicit_done: true });",
+        "test(function() {}, 'acceptable test');",
+        "onload = function() {",
+        "  done();",
+        "  test(function() {}, 'this test is late and should be ignored');",
+        "};",
+        "</" + "script>"
+    ].join("\n");
+    var iframe = document.createElement("iframe");
+
+    document.body.appendChild(iframe);
+    window.childReady = t.step_func(function(childWindow) {
+        childWindow.add_completion_callback(t.step_func(function(tests, status) {
+            t.step_timeout(t.step_func(function() {
+                assert_equals(tests.length, 1);
+                assert_equals(tests[0].name, "acceptable test");
+                assert_equals(status.status, status.OK);
+                t.done();
+            }), 0);
+        }));
+    });
+
+    iframe.contentDocument.open();
+    iframe.contentDocument.write(source);
+    iframe.contentDocument.close();
+});
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/promise_setup-timeout.html b/testing/web-platform/tests/resources/test/tests/unit/promise_setup-timeout.html
new file mode 100644
index 0000000000..c4947feef4
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/promise_setup-timeout.html
@@ -0,0 +1,28 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="timeout" content="long">
+  <script src="/resources/testharness.js"></script>
+  <script src="../../nested-testharness.js"></script>
+  <title>promise_setup - timeout</title>
+</head>
+<body>
+<script>
+'use strict';
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => {}, 'before');
+        promise_setup(() => new Promise(() => {}));
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'TIMEOUT');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'timeout when returned promise does not settle');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/promise_setup.html b/testing/web-platform/tests/resources/test/tests/unit/promise_setup.html
new file mode 100644
index 0000000000..2abb10a476
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/promise_setup.html
@@ -0,0 +1,333 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="/resources/testharness.js"></script>
+  <script src="../../nested-testharness.js"></script>
+  <title>promise_setup</title>
+</head>
+<body>
+<script>
+'use strict';
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup({});
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, undefined);
+    });
+}, 'Error when no function provided');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => {}, 'before');
+        promise_setup(() => Promise.resolve(), {});
+        promise_test(() => Promise.resolve(), 'after');
+        throw new Error('this error is expected');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'Does not apply unspecified configuration properties');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        var properties = {
+          allow_uncaught_exception: true
+        };
+        test(() => {}, 'before');
+        promise_setup(() => Promise.resolve(), properties);
+        promise_test(() => Promise.resolve(), 'after');
+        throw new Error('this error is expected');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'Ignores configuration properties when some tests have already run');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        var properties = {
+          allow_uncaught_exception: true
+        };
+        promise_setup(() => Promise.resolve(), properties);
+        promise_test(() => {
+          return new Promise((resolve) => {
+            setTimeout(() => {
+              resolve();
+              throw new Error('this error is expected');
+            });
+          });
+        }, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'Honors configuration properties');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup(() => { throw new Error('this error is expected'); });
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for synchronous exceptions');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup(() => undefined);
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for missing return value');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        var noThen = Promise.resolve();
+        noThen.then = undefined;
+        promise_setup(() => noThen);
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for non-thenable return value');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        var poisonedThen = {
+          get then() {
+            throw new Error('this error is expected');
+          }
+        };
+        promise_setup(() => poisonedThen);
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for "poisoned" `then` property');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        var badThen = {
+          then() {
+            throw new Error('this error is expected');
+          }
+        };
+        promise_setup(() => badThen);
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for synchronous error from `then` method');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup(() => Promise.resolve());
+        test(() => {}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, undefined);
+    });
+}, 'Error for subsequent invocation of `test`');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup(() => Promise.resolve());
+        async_test((t) => t.done(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, undefined);
+    });
+}, 'Error for subsequent invocation of `async_test`');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        // Ensure that the harness error is the result of explicit error
+        // handling
+        setup({ allow_uncaught_exception: true });
+
+        test(() => {}, 'before');
+        promise_setup(() => Promise.reject());
+        promise_test(() => Promise.resolve(), 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'NOTRUN');
+    });
+}, 'Error for rejected promise');
+
+promise_test(() => {
+  var expected_sequence = [
+    'test body',
+    'promise_setup begin',
+    'promise_setup end',
+    'promise_test body'
+  ];
+  var actual_sequence = window.actual_sequence = [];
+
+  return makeTest(
+      () => {
+        test(() => { parent.actual_sequence.push('test body'); }, 'before');
+        promise_setup(() => {
+          parent.actual_sequence.push('promise_setup begin');
+
+          return Promise.resolve()
+            .then(() => new Promise((resolve) => setTimeout(resolve, 300)))
+            .then(() => parent.actual_sequence.push('promise_setup end'));
+        });
+        promise_test(() => {
+          parent.actual_sequence.push('promise_test body');
+          return Promise.resolve();
+        }, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+      assert_array_equals(actual_sequence, expected_sequence);
+    });
+}, 'Waits for promise to settle');
+
+promise_test(() => {
+  var expected_sequence = [
+    'promise_test 1 begin',
+    'promise_test 1 end',
+    'promise_setup begin',
+    'promise_setup end',
+    'promise_test 2 body'
+  ];
+  var actual_sequence = window.actual_sequence = [];
+
+  return makeTest(
+      () => {
+        promise_test((t) => {
+          parent.actual_sequence.push('promise_test 1 begin');
+
+          return Promise.resolve()
+            .then(() => new Promise((resolve) => t.step_timeout(resolve, 300)))
+            .then(() => parent.actual_sequence.push('promise_test 1 end'));
+        }, 'before');
+        promise_setup(() => {
+          parent.actual_sequence.push('promise_setup begin');
+
+          return Promise.resolve()
+            .then(() => new Promise((resolve) => setTimeout(resolve, 300)))
+            .then(() => parent.actual_sequence.push('promise_setup end'));
+        });
+        promise_test(() => {
+          parent.actual_sequence.push('promise_test 2 body');
+          return Promise.resolve();
+        }, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.after, 'PASS');
+      assert_array_equals(actual_sequence, expected_sequence);
+    });
+}, 'Waits for existing promise_test to complete');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        var properties = { allow_uncaught_exception: true };
+        promise_test(() => {
+          return new Promise((resolve) => {
+            setTimeout(() => {
+              resolve();
+              throw new Error('this error is expected');
+            });
+          });
+        }, 'before');
+        promise_setup(() => Promise.resolve(), properties);
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'ERROR');
+      assert_equals(tests.before, 'PASS');
+    });
+}, 'Defers application of setup properties');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/single_test.html b/testing/web-platform/tests/resources/test/tests/unit/single_test.html
new file mode 100644
index 0000000000..ff766e66ce
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/single_test.html
@@ -0,0 +1,94 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="timeout" content="long">
+  <script src="/resources/testharness.js"></script>
+  <script src="../../nested-testharness.js"></script>
+  <title>single_test</title>
+</head>
+<body>
+<script>
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        done();
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'PASS');
+    });
+}, 'Expected usage');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        throw new Error('this error is expected');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'FAIL');
+    });
+}, 'Uncaught exception');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        Promise.reject(new Error('this error is expected'));
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'FAIL');
+    });
+}, 'Unhandled rejection');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        test(function() {}, 'sync test');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'FAIL');
+      assert_equals(
+        Object.keys(tests).length, 1, 'no additional subtests created'
+      );
+    });
+}, 'Erroneous usage: subtest declaration (synchronous test)');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        async_test(function(t) { t.done(); }, 'async test');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'FAIL');
+      assert_equals(
+        Object.keys(tests).length, 1, 'no additional subtests created'
+      );
+    });
+}, 'Erroneous usage: subtest declaration (asynchronous test)');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        setup({ single_test: true });
+        promise_test(function() { return Promise.resolve(); }, 'promise test');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness, 'OK');
+      assert_equals(tests['Document title'], 'FAIL');
+      assert_equals(
+        Object.keys(tests).length, 1, 'no additional subtests created'
+      );
+    });
+}, 'Erroneous usage: subtest declaration (promise test)');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/test-return-restrictions.html b/testing/web-platform/tests/resources/test/tests/unit/test-return-restrictions.html
new file mode 100644
index 0000000000..0295c5214d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/test-return-restrictions.html
@@ -0,0 +1,156 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="/resources/testharness.js"></script>
+  <title>Restrictions on return value from `test`</title>
+</head>
+<body>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: {
+        status: getEnumProp(status, status.status),
+        message: status.message
+      },
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => undefined, 'before');
+        test(() => null, 'null');
+        test(() => undefined, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "null" passed a function to `test` that returned a value.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.null, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'test returning `null`');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => undefined, 'before');
+        test(() => ({}), 'object');
+        test(() => undefined, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "object" passed a function to `test` that returned a value.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.object, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'test returning an ordinary object');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => undefined, 'before');
+        test(() => Promise.resolve(5), 'thenable');
+        test(() => undefined, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "thenable" passed a function to `test` that returned a value. ' +
+        'Consider using `promise_test` instead when using Promises or async/await.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.thenable, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'test returning a thenable object');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => undefined, 'before');
+        test(() => {
+          const iframe = document.createElement('iframe');
+          iframe.setAttribute('sandbox', '');
+          document.body.appendChild(iframe);
+          return iframe.contentWindow;
+        }, 'restricted');
+        test(() => undefined, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'ERROR');
+      assert_equals(
+        harness.message,
+        'Test named "restricted" passed a function to `test` that returned a value.'
+      );
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests.restricted, 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'test returning a restricted object');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/throwing-assertions.html b/testing/web-platform/tests/resources/test/tests/unit/throwing-assertions.html
new file mode 100644
index 0000000000..a36a56043c
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/throwing-assertions.html
@@ -0,0 +1,268 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <meta name="timeout" content="long">
+  <script src="/resources/testharness.js"></script>
+  <title>Test the methods that make assertions about exceptions</title>
+</head>
+<body>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: getEnumProp(status, status.status),
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(TypeError, () => { throw new TypeError(); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_js on a TypeError');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(RangeError, () => { throw new RangeError(); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_js on a RangeError');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(TypeError, () => { throw new RangeError(); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_js on a TypeError when RangeError is thrown');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(Error, () => { throw new TypeError(); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_js on an Error when TypeError is thrown');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(Error,
+                       () => { throw new DOMException("hello", "Error"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_js on an Error when a DOMException is thrown');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_js(SyntaxError,
+                       () => { throw new DOMException("hey", "SyntaxError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_js on a SyntaxError when a DOMException is thrown');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom("SyntaxError",
+                        () => { throw new DOMException("x", "SyntaxError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_dom basic sanity');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom(12,
+                        () => { throw new DOMException("x", "SyntaxError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_dom with numeric code');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom("SYNTAX_ERR",
+                        () => { throw new DOMException("x", "SyntaxError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_dom with string name for code');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom("DataError",
+                        () => { throw new DOMException("x", "DataError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_dom for a code-less DOMException type');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom("NoSuchError",
+                        () => { throw new DOMException("x", "NoSuchError"); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_dom for a nonexistent DOMException type');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_dom("SyntaxError", () => { throw new SyntaxError(); });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_dom when a non-DOM exception is thrown');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_exactly(5, () => { throw 5; });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_exactly with number');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_exactly("foo", () => { throw "foo"; });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_exactly with string');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_exactly({}, () => { throw {}; });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_exactly with different objects');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      var obj = {};
+      assert_throws_exactly(obj, () => { throw obj; });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'PASS');
+  });
+}, 'assert_throws_exactly with same object');
+
+promise_test(() => {
+  return makeTest(() => {
+    test(() => {
+      assert_throws_exactly(TypeError, () => { throw new TypeError; });
+    });
+  }).then(({harness, tests}) => {
+    assert_equals(harness, 'OK');
+    assert_equals(tests['Document title'], 'FAIL');
+  });
+}, 'assert_throws_exactly with bogus TypeError bits ');
+
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tests/unit/unpaired-surrogates.html b/testing/web-platform/tests/resources/test/tests/unit/unpaired-surrogates.html
new file mode 100644
index 0000000000..b232111326
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/unpaired-surrogates.html
@@ -0,0 +1,143 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script src="/resources/testharness.js"></script>
+  <title>Restrictions on return value from `test`</title>
+</head>
+<body>
+<script>
+function makeTest(...bodies) {
+  const closeScript = '<' + '/script>';
+  let src = `
+<!DOCTYPE HTML>
+<html>
+<head>
+<title>Document title</title>
+<script src="/resources/testharness.js?${Math.random()}">${closeScript}
+</head>
+
+<body>
+<div id="log"></div>`;
+  bodies.forEach((body) => {
+    src += '<script>(' + body + ')();' + closeScript;
+  });
+
+  const iframe = document.createElement('iframe');
+
+  document.body.appendChild(iframe);
+  iframe.contentDocument.write(src);
+
+  return new Promise((resolve) => {
+    window.addEventListener('message', function onMessage(e) {
+      if (e.source !== iframe.contentWindow) {
+        return;
+      }
+      if (!e.data || e.data.type !=='complete') {
+        return;
+      }
+      window.removeEventListener('message', onMessage);
+      resolve(e.data);
+    });
+
+    iframe.contentDocument.close();
+  }).then(({ tests, status }) => {
+    const summary = {
+      harness: {
+        status: getEnumProp(status, status.status),
+        message: status.message
+      },
+      tests: {}
+    };
+
+    tests.forEach((test) => {
+      summary.tests[test.name] = getEnumProp(test, test.status);
+    });
+
+    return summary;
+  });
+}
+
+function getEnumProp(object, value) {
+  for (let property in object) {
+    if (!/^[A-Z]+$/.test(property)) {
+      continue;
+    }
+
+    if (object[property] === value) {
+      return property;
+    }
+  }
+}
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => {}, 'before');
+        test(() => {}, 'U+d7ff is not modified: \ud7ff');
+        test(() => {}, 'U+e000 is not modified: \ue000');
+        test(() => {}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'OK');
+      assert_equals(harness.message, null);
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests['U+d7ff is not modified: \ud7ff'], 'PASS');
+      assert_equals(tests['U+e000 is not modified: \ue000'], 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'sub-test names which include valid code units');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => {}, 'before');
+        test(() => {}, 'U+d800U+dfff is not modified: \ud800\udfff');
+        test(() => {}, 'U+dbffU+dc00 is not modified: \udbff\udc00');
+        test(() => {}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'OK');
+      assert_equals(harness.message, null);
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests['U+d800U+dfff is not modified: \ud800\udfff'], 'PASS');
+      assert_equals(tests['U+dbffU+dc00 is not modified: \udbff\udc00'], 'PASS');
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'sub-test names which include paired surrogates');
+
+promise_test(() => {
+  return makeTest(
+      () => {
+        test(() => {}, 'before');
+        test(() => {}, 'U+d800 must be sanitized: \ud800');
+        test(() => {}, 'U+d800U+d801 must be sanitized: \ud800\ud801');
+        test(() => {}, 'U+dfff must be sanitized: \udfff');
+        test(() => {}, 'U+dc00U+d800U+dc00U+d800 must be sanitized: \udc00\ud800\udc00\ud800');
+        test(() => {}, 'U+dbffU+dfffU+dfff must be sanitized: \udbff\udfff\udfff');
+        test(() => {}, 'after');
+      }
+    ).then(({harness, tests}) => {
+      assert_equals(harness.status, 'OK');
+      assert_equals(harness.message, null);
+      assert_equals(tests.before, 'PASS');
+      assert_equals(tests['U+d800 must be sanitized: U+d800'], 'PASS');
+      assert_equals(tests['U+dfff must be sanitized: U+dfff'], 'PASS');
+      assert_equals(
+        tests['U+d800U+d801 must be sanitized: U+d800U+d801'],
+        'PASS'
+      );
+      assert_equals(
+        tests['U+dc00U+d800U+dc00U+d800 must be sanitized: U+dc00\ud800\udc00U+d800'],
+        'PASS'
+      );
+      assert_equals(
+        tests['U+dbffU+dfffU+dfff must be sanitized: \udbff\udfffU+dfff'],
+        'PASS'
+      );
+      assert_equals(tests.after, 'PASS');
+    });
+}, 'sub-test names which include unpaired surrogates');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/resources/test/tox.ini b/testing/web-platform/tests/resources/test/tox.ini
new file mode 100644
index 0000000000..4fbeb67fb5
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tox.ini
@@ -0,0 +1,13 @@
+[tox]
+envlist = py37,py38,py39,py310
+skipsdist=True
+
+[testenv]
+passenv=DISPLAY # Necessary for the spawned GeckoDriver process to connect to
+                # the appropriate display.
+
+deps =
+  -r{toxinidir}/../../tools/requirements_pytest.txt
+  -r{toxinidir}/requirements.txt
+
+commands = pytest -vv {posargs}
diff --git a/testing/web-platform/tests/resources/test/wptserver.py b/testing/web-platform/tests/resources/test/wptserver.py
new file mode 100644
index 0000000000..1f913dd96d
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/wptserver.py
@@ -0,0 +1,58 @@
+import logging
+import os
+import subprocess
+import time
+import sys
+import urllib
+
+
+class WPTServer(object):
+    def __init__(self, wpt_root):
+        self.logger = logging.getLogger()
+        self.wpt_root = wpt_root
+
+        # This is a terrible hack to get the default config of wptserve.
+        sys.path.insert(0, os.path.join(wpt_root, "tools"))
+        from serve.serve import build_config
+        with build_config(self.logger) as config:
+            self.host = config["browser_host"]
+            self.http_port = config["ports"]["http"][0]
+            self.https_port = config["ports"]["https"][0]
+
+        self.base_url = 'http://%s:%s' % (self.host, self.http_port)
+        self.https_base_url = 'https://%s:%s' % (self.host, self.https_port)
+
+    def start(self, ssl_context):
+        self.devnull = open(os.devnull, 'w')
+        wptserve_cmd = [os.path.join(self.wpt_root, 'wpt'), 'serve']
+        if sys.executable:
+            wptserve_cmd[0:0] = [sys.executable]
+        self.logger.info('Executing %s' % ' '.join(wptserve_cmd))
+        self.proc = subprocess.Popen(
+            wptserve_cmd,
+            stderr=self.devnull,
+            cwd=self.wpt_root)
+
+        for retry in range(5):
+            # Exponential backoff.
+            time.sleep(2 ** retry)
+            exit_code = self.proc.poll()
+            if exit_code != None:
+                logging.warning('Command "%s" exited with %s', ' '.join(wptserve_cmd), exit_code)
+                break
+            try:
+                urllib.request.urlopen(self.base_url, timeout=1)
+                urllib.request.urlopen(self.https_base_url, timeout=1, context=ssl_context)
+                return
+            except urllib.error.URLError:
+                pass
+
+        raise Exception('Could not start wptserve on %s' % self.base_url)
+
+    def stop(self):
+        self.proc.terminate()
+        self.proc.wait()
+        self.devnull.close()
+
+    def url(self, abs_path):
+        return self.https_base_url + '/' + os.path.relpath(abs_path, self.wpt_root)
diff --git a/testing/web-platform/tests/resources/testdriver-actions.js b/testing/web-platform/tests/resources/testdriver-actions.js
new file mode 100644
index 0000000000..3e5ba74b4c
--- /dev/null
+++ b/testing/web-platform/tests/resources/testdriver-actions.js
@@ -0,0 +1,599 @@
+(function() {
+  let sourceNameIdx = 0;
+
+  /**
+   * @class
+   * Builder for creating a sequence of actions
+   *
+   *
+   * The actions are dispatched once
+   * :js:func:`test_driver.Actions.send` is called. This returns a
+   * promise which resolves once the actions are complete.
+   *
+   * The other methods on :js:class:`test_driver.Actions` object are
+   * used to build the sequence of actions that will be sent. These
+   * return the `Actions` object itself, so the actions sequence can
+   * be constructed by chaining method calls.
+   *
+   * Internally :js:func:`test_driver.Actions.send` invokes
+   * :js:func:`test_driver.action_sequence`.
+   *
+   * @example
+   * let text_box = document.getElementById("text");
+   *
+   * let actions = new test_driver.Actions()
+   *    .pointerMove(0, 0, {origin: text_box})
+   *    .pointerDown()
+   *    .pointerUp()
+   *    .addTick()
+   *    .keyDown("p")
+   *    .keyUp("p");
+   *
+   * await actions.send();
+   *
+   * @param {number} [defaultTickDuration] - The default duration of a
+   * tick. Be default this is set ot 16ms, which is one frame time
+   * based on 60Hz display.
+   */
+  function Actions(defaultTickDuration=16) {
+    this.sourceTypes = new Map([["key", KeySource],
+                                ["pointer", PointerSource],
+                                ["wheel", WheelSource],
+                                ["none", GeneralSource]]);
+    this.sources = new Map();
+    this.sourceOrder = [];
+    for (let sourceType of this.sourceTypes.keys()) {
+      this.sources.set(sourceType, new Map());
+    }
+    this.currentSources = new Map();
+    for (let sourceType of this.sourceTypes.keys()) {
+      this.currentSources.set(sourceType, null);
+    }
+    this.createSource("none");
+    this.tickIdx = 0;
+    this.defaultTickDuration = defaultTickDuration;
+    this.context = null;
+  }
+
+  Actions.prototype = {
+    ButtonType: {
+      LEFT: 0,
+      MIDDLE: 1,
+      RIGHT: 2,
+      BACK: 3,
+      FORWARD: 4,
+    },
+
+    /**
+     * Generate the action sequence suitable for passing to
+     * test_driver.action_sequence
+     *
+     * @returns {Array} Array of WebDriver-compatible actions sequences
+     */
+    serialize: function() {
+      let actions = [];
+      for (let [sourceType, sourceName] of this.sourceOrder) {
+        let source = this.sources.get(sourceType).get(sourceName);
+        let serialized = source.serialize(this.tickIdx + 1, this.defaultTickDuration);
+        if (serialized) {
+          serialized.id = sourceName;
+          actions.push(serialized);
+        }
+      }
+      return actions;
+    },
+
+    /**
+     * Generate and send the action sequence
+     *
+     * @returns {Promise} fulfilled after the sequence is executed,
+     *                    rejected if any actions fail.
+     */
+    send: function() {
+      let actions;
+      try {
+        actions = this.serialize();
+      } catch(e) {
+        return Promise.reject(e);
+      }
+      return test_driver.action_sequence(actions, this.context);
+    },
+
+    /**
+     * Set the context for the actions
+     *
+     * @param {WindowProxy} context - Context in which to run the action sequence
+     */
+    setContext: function(context) {
+      this.context = context;
+      return this;
+    },
+
+    /**
+     * Get the action source with a particular source type and name.
+     * If no name is passed, a new source with the given type is
+     * created.
+     *
+     * @param {String} type - Source type ('none', 'key', 'pointer', or 'wheel')
+     * @param {String?} name - Name of the source
+     * @returns {Source} Source object for that source.
+     */
+    getSource: function(type, name) {
+      if (!this.sources.has(type)) {
+        throw new Error(`${type} is not a valid action type`);
+      }
+      if (name === null || name === undefined) {
+        name = this.currentSources.get(type);
+      }
+      if (name === null || name === undefined) {
+        return this.createSource(type, null);
+      }
+      return this.sources.get(type).get(name);
+    },
+
+    setSource: function(type, name) {
+      if (!this.sources.has(type)) {
+        throw new Error(`${type} is not a valid action type`);
+      }
+      if (!this.sources.get(type).has(name)) {
+        throw new Error(`${name} is not a valid source for ${type}`);
+      }
+      this.currentSources.set(type, name);
+      return this;
+    },
+
+    /**
+     * Add a new key input source with the given name
+     *
+     * @param {String} name - Name of the key source
+     * @param {Bool} set - Set source as the default key source
+     * @returns {Actions}
+     */
+    addKeyboard: function(name, set=true) {
+      this.createSource("key", name);
+      if (set) {
+        this.setKeyboard(name);
+      }
+      return this;
+    },
+
+    /**
+     * Set the current default key source
+     *
+     * @param {String} name - Name of the key source
+     * @returns {Actions}
+     */
+    setKeyboard: function(name) {
+      this.setSource("key", name);
+      return this;
+    },
+
+    /**
+     * Add a new pointer input source with the given name
+     *
+     * @param {String} type - Name of the pointer source
+     * @param {String} pointerType - Type of pointing device
+     * @param {Bool} set - Set source as the default pointer source
+     * @returns {Actions}
+     */
+    addPointer: function(name, pointerType="mouse", set=true) {
+      this.createSource("pointer", name, {pointerType: pointerType});
+      if (set) {
+        this.setPointer(name);
+      }
+      return this;
+    },
+
+    /**
+     * Set the current default pointer source
+     *
+     * @param {String} name - Name of the pointer source
+     * @returns {Actions}
+     */
+    setPointer: function(name) {
+      this.setSource("pointer", name);
+      return this;
+    },
+
+    /**
+     * Add a new wheel input source with the given name
+     *
+     * @param {String} type - Name of the wheel source
+     * @param {Bool} set - Set source as the default wheel source
+     * @returns {Actions}
+     */
+    addWheel: function(name, set=true) {
+      this.createSource("wheel", name);
+      if (set) {
+        this.setWheel(name);
+      }
+      return this;
+    },
+
+    /**
+     * Set the current default wheel source
+     *
+     * @param {String} name - Name of the wheel source
+     * @returns {Actions}
+     */
+    setWheel: function(name) {
+      this.setSource("wheel", name);
+      return this;
+    },
+
+    createSource: function(type, name, parameters={}) {
+      if (!this.sources.has(type)) {
+        throw new Error(`${type} is not a valid action type`);
+      }
+      let sourceNames = new Set();
+      for (let [_, name] of this.sourceOrder) {
+        sourceNames.add(name);
+      }
+      if (!name) {
+        do {
+          name = "" + sourceNameIdx++;
+        } while (sourceNames.has(name))
+      } else {
+        if (sourceNames.has(name)) {
+          throw new Error(`Alreay have a source of type ${type} named ${name}.`);
+        }
+      }
+      this.sources.get(type).set(name, new (this.sourceTypes.get(type))(parameters));
+      this.currentSources.set(type, name);
+      this.sourceOrder.push([type, name]);
+      return this.sources.get(type).get(name);
+    },
+
+    /**
+     * Insert a new actions tick
+     *
+     * @param {Number?} duration - Minimum length of the tick in ms.
+     * @returns {Actions}
+     */
+    addTick: function(duration) {
+      this.tickIdx += 1;
+      if (duration) {
+        this.pause(duration);
+      }
+      return this;
+    },
+
+    /**
+     * Add a pause to the current tick
+     *
+     * @param {Number?} duration - Minimum length of the tick in ms.
+     * @param {String} sourceType - source type
+     * @param {String?} sourceName - Named key, pointer or wheel source to use
+     *                               or null for the default key, pointer or
+     *                               wheel source
+     * @returns {Actions}
+     */
+    pause: function(duration=0, sourceType="none", {sourceName=null}={}) {
+      if (sourceType=="none")
+        this.getSource("none").addPause(this, duration);
+      else
+        this.getSource(sourceType, sourceName).addPause(this, duration);
+      return this;
+    },
+
+    /**
+     * Create a keyDown event for the current default key source
+     *
+     * @param {String} key - Key to press
+     * @param {String?} sourceName - Named key source to use or null for the default key source
+     * @returns {Actions}
+     */
+    keyDown: function(key, {sourceName=null}={}) {
+      let source = this.getSource("key", sourceName);
+      source.keyDown(this, key);
+      return this;
+    },
+
+    /**
+     * Create a keyDown event for the current default key source
+     *
+     * @param {String} key - Key to release
+     * @param {String?} sourceName - Named key source to use or null for the default key source
+     * @returns {Actions}
+     */
+    keyUp: function(key, {sourceName=null}={}) {
+      let source = this.getSource("key", sourceName);
+      source.keyUp(this, key);
+      return this;
+    },
+
+    /**
+     * Create a pointerDown event for the current default pointer source
+     *
+     * @param {String} button - Button to press
+     * @param {String?} sourceName - Named pointer source to use or null for the default
+     *                               pointer source
+     * @returns {Actions}
+     */
+    pointerDown: function({button=this.ButtonType.LEFT, sourceName=null,
+                           width, height, pressure, tangentialPressure,
+                           tiltX, tiltY, twist, altitudeAngle, azimuthAngle}={}) {
+      let source = this.getSource("pointer", sourceName);
+      source.pointerDown(this, button, width, height, pressure, tangentialPressure,
+                         tiltX, tiltY, twist, altitudeAngle, azimuthAngle);
+      return this;
+    },
+
+    /**
+     * Create a pointerUp event for the current default pointer source
+     *
+     * @param {String} button - Button to release
+     * @param {String?} sourceName - Named pointer source to use or null for the default pointer
+     *                               source
+     * @returns {Actions}
+     */
+    pointerUp: function({button=this.ButtonType.LEFT, sourceName=null}={}) {
+      let source = this.getSource("pointer", sourceName);
+      source.pointerUp(this, button);
+      return this;
+    },
+
+    /**
+     * Create a move event for the current default pointer source
+     *
+     * @param {Number} x - Destination x coordinate
+     * @param {Number} y - Destination y coordinate
+     * @param {String|Element} origin - Origin of the coordinate system.
+     *                                  Either "pointer", "viewport" or an Element
+     * @param {Number?} duration - Time in ms for the move
+     * @param {String?} sourceName - Named pointer source to use or null for the default pointer
+     *                               source
+     * @returns {Actions}
+     */
+    pointerMove: function(x, y,
+                          {origin="viewport", duration, sourceName=null,
+                           width, height, pressure, tangentialPressure,
+                           tiltX, tiltY, twist, altitudeAngle, azimuthAngle}={}) {
+      let source = this.getSource("pointer", sourceName);
+      source.pointerMove(this, x, y, duration, origin, width, height, pressure,
+                         tangentialPressure, tiltX, tiltY, twist, altitudeAngle,
+                         azimuthAngle);
+      return this;
+    },
+
+    /**
+     * Create a scroll event for the current default wheel source
+     *
+     * @param {Number} x - mouse cursor x coordinate
+     * @param {Number} y - mouse cursor y coordinate
+     * @param {Number} deltaX - scroll delta value along the x-axis in pixels
+     * @param {Number} deltaY - scroll delta value along the y-axis in pixels
+     * @param {String|Element} origin - Origin of the coordinate system.
+     *                                  Either "viewport" or an Element
+     * @param {Number?} duration - Time in ms for the scroll
+     * @param {String?} sourceName - Named wheel source to use or null for the
+     *                               default wheel source
+     * @returns {Actions}
+     */
+    scroll: function(x, y, deltaX, deltaY,
+                     {origin="viewport", duration, sourceName=null}={}) {
+      let source = this.getSource("wheel", sourceName);
+      source.scroll(this, x, y, deltaX, deltaY, duration, origin);
+      return this;
+    },
+  };
+
+  function GeneralSource() {
+    this.actions = new Map();
+  }
+
+  GeneralSource.prototype = {
+    serialize: function(tickCount, defaultTickDuration) {
+      let actions = [];
+      let data = {"type": "none", "actions": actions};
+      for (let i=0; i<tickCount; i++) {
+        if (this.actions.has(i)) {
+          actions.push(this.actions.get(i));
+        } else {
+          actions.push({"type": "pause", duration: defaultTickDuration});
+        }
+      }
+      return data;
+    },
+
+    addPause: function(actions, duration) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        throw new Error(`Already have a pause action for the current tick`);
+      }
+      this.actions.set(tick, {type: "pause", duration: duration});
+    },
+  };
+
+  function KeySource() {
+    this.actions = new Map();
+  }
+
+  KeySource.prototype = {
+    serialize: function(tickCount) {
+      if (!this.actions.size) {
+        return undefined;
+      }
+      let actions = [];
+      let data = {"type": "key", "actions": actions};
+      for (let i=0; i<tickCount; i++) {
+        if (this.actions.has(i)) {
+          actions.push(this.actions.get(i));
+        } else {
+          actions.push({"type": "pause"});
+        }
+      }
+      return data;
+    },
+
+    keyDown: function(actions, key) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "keyDown", value: key});
+    },
+
+    keyUp: function(actions, key) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "keyUp", value: key});
+    },
+
+    addPause: function(actions, duration) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "pause", duration: duration});
+    },
+  };
+
+  function PointerSource(parameters={pointerType: "mouse"}) {
+    let pointerType = parameters.pointerType || "mouse";
+    if (!["mouse", "pen", "touch"].includes(pointerType)) {
+      throw new Error(`Invalid pointerType ${pointerType}`);
+    }
+    this.type = pointerType;
+    this.actions = new Map();
+  }
+
+  function setPointerProperties(action, width, height, pressure, tangentialPressure,
+                                tiltX, tiltY, twist, altitudeAngle, azimuthAngle) {
+    if (width) {
+      action.width = width;
+    }
+    if (height) {
+      action.height = height;
+    }
+    if (pressure) {
+      action.pressure = pressure;
+    }
+    if (tangentialPressure) {
+      action.tangentialPressure = tangentialPressure;
+    }
+    if (tiltX) {
+      action.tiltX = tiltX;
+    }
+    if (tiltY) {
+      action.tiltY = tiltY;
+    }
+    if (twist) {
+      action.twist = twist;
+    }
+    if (altitudeAngle) {
+      action.altitudeAngle = altitudeAngle;
+    }
+    if (azimuthAngle) {
+      action.azimuthAngle = azimuthAngle;
+    }
+    return action;
+  }
+
+  PointerSource.prototype = {
+    serialize: function(tickCount) {
+      if (!this.actions.size) {
+        return undefined;
+      }
+      let actions = [];
+      let data = {"type": "pointer", "actions": actions, "parameters": {"pointerType": this.type}};
+      for (let i=0; i<tickCount; i++) {
+        if (this.actions.has(i)) {
+          actions.push(this.actions.get(i));
+        } else {
+          actions.push({"type": "pause"});
+        }
+      }
+      return data;
+    },
+
+    pointerDown: function(actions, button, width, height, pressure, tangentialPressure,
+                          tiltX, tiltY, twist, altitudeAngle, azimuthAngle) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      let actionProperties = setPointerProperties({type: "pointerDown", button}, width, height,
+                                                  pressure, tangentialPressure, tiltX, tiltY,
+                                                  twist, altitudeAngle, azimuthAngle);
+      this.actions.set(tick, actionProperties);
+    },
+
+    pointerUp: function(actions, button) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "pointerUp", button});
+    },
+
+    pointerMove: function(actions, x, y, duration, origin, width, height, pressure,
+                          tangentialPressure, tiltX, tiltY, twist, altitudeAngle, azimuthAngle) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      let moveAction = {type: "pointerMove", x, y, origin};
+      if (duration) {
+        moveAction.duration = duration;
+      }
+      let actionProperties = setPointerProperties(moveAction, width, height, pressure,
+                                                  tangentialPressure, tiltX, tiltY, twist,
+                                                  altitudeAngle, azimuthAngle);
+      this.actions.set(tick, actionProperties);
+    },
+
+    addPause: function(actions, duration) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "pause", duration: duration});
+    },
+  };
+
+  function WheelSource() {
+    this.actions = new Map();
+  }
+
+  WheelSource.prototype = {
+    serialize: function(tickCount) {
+      if (!this.actions.size) {
+        return undefined;
+      }
+      let actions = [];
+      let data = {"type": "wheel", "actions": actions};
+      for (let i=0; i<tickCount; i++) {
+        if (this.actions.has(i)) {
+          actions.push(this.actions.get(i));
+        } else {
+          actions.push({"type": "pause"});
+        }
+      }
+      return data;
+    },
+
+    scroll: function(actions, x, y, deltaX, deltaY, duration, origin) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "scroll", x, y, deltaX, deltaY, origin});
+      if (duration) {
+        this.actions.get(tick).duration = duration;
+      }
+    },
+
+    addPause: function(actions, duration) {
+      let tick = actions.tickIdx;
+      if (this.actions.has(tick)) {
+        tick = actions.addTick().tickIdx;
+      }
+      this.actions.set(tick, {type: "pause", duration: duration});
+    },
+  };
+
+  test_driver.Actions = Actions;
+})();
diff --git a/testing/web-platform/tests/resources/testdriver-vendor.js b/testing/web-platform/tests/resources/testdriver-vendor.js
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/testing/web-platform/tests/resources/testdriver-vendor.js
diff --git a/testing/web-platform/tests/resources/testdriver-vendor.js.headers b/testing/web-platform/tests/resources/testdriver-vendor.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/testdriver-vendor.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600
diff --git a/testing/web-platform/tests/resources/testdriver.js b/testing/web-platform/tests/resources/testdriver.js
new file mode 100644
index 0000000000..446b033b0a
--- /dev/null
+++ b/testing/web-platform/tests/resources/testdriver.js
@@ -0,0 +1,809 @@
+(function() {
+    "use strict";
+    var idCounter = 0;
+    let testharness_context = null;
+
+    function getInViewCenterPoint(rect) {
+        var left = Math.max(0, rect.left);
+        var right = Math.min(window.innerWidth, rect.right);
+        var top = Math.max(0, rect.top);
+        var bottom = Math.min(window.innerHeight, rect.bottom);
+
+        var x = 0.5 * (left + right);
+        var y = 0.5 * (top + bottom);
+
+        return [x, y];
+    }
+
+    function getPointerInteractablePaintTree(element) {
+        let elementDocument = element.ownerDocument;
+        if (!elementDocument.contains(element)) {
+            return [];
+        }
+
+        var rectangles = element.getClientRects();
+
+        if (rectangles.length === 0) {
+            return [];
+        }
+
+        var centerPoint = getInViewCenterPoint(rectangles[0]);
+
+        if ("elementsFromPoint" in elementDocument) {
+            return elementDocument.elementsFromPoint(centerPoint[0], centerPoint[1]);
+        } else if ("msElementsFromPoint" in elementDocument) {
+            var rv = elementDocument.msElementsFromPoint(centerPoint[0], centerPoint[1]);
+            return Array.prototype.slice.call(rv ? rv : []);
+        } else {
+            throw new Error("document.elementsFromPoint unsupported");
+        }
+    }
+
+    function inView(element) {
+        var pointerInteractablePaintTree = getPointerInteractablePaintTree(element);
+        return pointerInteractablePaintTree.indexOf(element) !== -1;
+    }
+
+
+    /**
+     * @namespace {test_driver}
+     */
+    window.test_driver = {
+        /**
+         * Set the context in which testharness.js is loaded
+         *
+         * @param {WindowProxy} context - the window containing testharness.js
+         **/
+        set_test_context: function(context) {
+          if (window.test_driver_internal.set_test_context) {
+            window.test_driver_internal.set_test_context(context);
+          }
+          testharness_context = context;
+        },
+
+        /**
+         * postMessage to the context containing testharness.js
+         *
+         * @param {Object} msg - the data to POST
+         **/
+        message_test: function(msg) {
+            let target = testharness_context;
+            if (testharness_context === null) {
+                target = window;
+            }
+            target.postMessage(msg, "*");
+        },
+
+        /**
+         * Trigger user interaction in order to grant additional privileges to
+         * a provided function.
+         *
+         * See `Tracking user activation
+         * <https://html.spec.whatwg.org/multipage/interaction.html#tracking-user-activation>`_.
+         *
+         * @example
+         * var mediaElement = document.createElement('video');
+         *
+         * test_driver.bless('initiate media playback', function () {
+         *   mediaElement.play();
+         * });
+         *
+         * @param {String} intent - a description of the action which must be
+         *                          triggered by user interaction
+         * @param {Function} action - code requiring escalated privileges
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled following user interaction and
+         *                    execution of the provided `action` function;
+         *                    rejected if interaction fails or the provided
+         *                    function throws an error
+         */
+        bless: function(intent, action, context=null) {
+            let contextDocument = context ? context.document : document;
+            var button = contextDocument.createElement("button");
+            button.innerHTML = "This test requires user interaction.<br />" +
+                "Please click here to allow " + intent + ".";
+            button.id = "wpt-test-driver-bless-" + (idCounter += 1);
+            const elem = contextDocument.body || contextDocument.documentElement;
+            elem.appendChild(button);
+
+            let wait_click = new Promise(resolve => button.addEventListener("click", resolve));
+
+            return test_driver.click(button)
+                .then(wait_click)
+                .then(function() {
+                    button.remove();
+
+                    if (typeof action === "function") {
+                        return action();
+                    }
+                    return null;
+                });
+        },
+
+        /**
+         * Triggers a user-initiated click
+         *
+         * If ``element`` isn't inside the
+         * viewport, it will be scrolled into view before the click
+         * occurs.
+         *
+         * If ``element`` is from a different browsing context, the
+         * command will be run in that context.
+         *
+         * Matches the behaviour of the `Element Click
+         * <https://w3c.github.io/webdriver/#element-click>`_
+         * WebDriver command.
+         *
+         * **Note:** If the element to be clicked does not have a
+         * unique ID, the document must not have any DOM mutations
+         * made between the function being called and the promise
+         * settling.
+         *
+         * @param {Element} element - element to be clicked
+         * @returns {Promise} fulfilled after click occurs, or rejected in
+         *                    the cases the WebDriver command errors
+         */
+        click: function(element) {
+            if (!inView(element)) {
+                element.scrollIntoView({behavior: "instant",
+                                        block: "end",
+                                        inline: "nearest"});
+            }
+
+            var pointerInteractablePaintTree = getPointerInteractablePaintTree(element);
+            if (pointerInteractablePaintTree.length === 0 ||
+                !element.contains(pointerInteractablePaintTree[0])) {
+                return Promise.reject(new Error("element click intercepted error"));
+            }
+
+            var rect = element.getClientRects()[0];
+            var centerPoint = getInViewCenterPoint(rect);
+            return window.test_driver_internal.click(element,
+                                                     {x: centerPoint[0],
+                                                      y: centerPoint[1]});
+        },
+
+        /**
+         * Deletes all cookies.
+         *
+         * Matches the behaviour of the `Delete All Cookies
+         * <https://w3c.github.io/webdriver/#delete-all-cookies>`_
+         * WebDriver command.
+         *
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after cookies are deleted, or rejected in
+         *                    the cases the WebDriver command errors
+         */
+        delete_all_cookies: function(context=null) {
+            return window.test_driver_internal.delete_all_cookies(context);
+        },
+
+        /**
+         * Get details for all cookies in the current context.
+         * See https://w3c.github.io/webdriver/#get-all-cookies
+         *
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} Returns an array of cookies objects as defined in the spec:
+         *                    https://w3c.github.io/webdriver/#cookies
+         */
+        get_all_cookies: function(context=null) {
+            return window.test_driver_internal.get_all_cookies(context);
+        },
+
+        /**
+         * Get details for a cookie in the current context by name if it exists.
+         * See https://w3c.github.io/webdriver/#get-named-cookie
+         *
+         * @param {String} name - The name of the cookie to get.
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} Returns the matching cookie as defined in the spec:
+         *                    https://w3c.github.io/webdriver/#cookies
+         *                    Rejected if no such cookie exists.
+         */
+         get_named_cookie: async function(name, context=null) {
+            let cookie = await window.test_driver_internal.get_named_cookie(name, context);
+            if (!cookie) {
+                throw new Error("no such cookie");
+            }
+            return cookie;
+        },
+
+        /**
+         * Get Computed Label for an element.
+         *
+         * This matches the behaviour of the
+         * `Get Computed Label
+         * <https://w3c.github.io/webdriver/#dfn-get-computed-label>`_
+         * WebDriver command.
+         *
+         * @param {Element} element
+         * @returns {Promise} fulfilled after the computed label is returned, or
+         *                    rejected in the cases the WebDriver command errors
+         */
+        get_computed_label: async function(element) {
+            let label = await window.test_driver_internal.get_computed_label(element);
+            return label;
+        },
+
+        /**
+         * Get Computed Role for an element.
+         *
+         * This matches the behaviour of the
+         * `Get Computed Label
+         * <https://w3c.github.io/webdriver/#dfn-get-computed-role>`_
+         * WebDriver command.
+         *
+         * @param {Element} element
+         * @returns {Promise} fulfilled after the computed role is returned, or
+         *                    rejected in the cases the WebDriver command errors
+         */
+        get_computed_role: async function(element) {
+            let role = await window.test_driver_internal.get_computed_role(element);
+            return role;
+        },
+
+        /**
+         * Send keys to an element.
+         *
+         * If ``element`` isn't inside the
+         * viewport, it will be scrolled into view before the click
+         * occurs.
+         *
+         * If ``element`` is from a different browsing context, the
+         * command will be run in that context.
+         *
+         * To send special keys, send the respective key's codepoint,
+         * as defined by `WebDriver
+         * <https://w3c.github.io/webdriver/#keyboard-actions>`_.  For
+         * example, the "tab" key is represented as "``\uE004``".
+         *
+         * **Note:** these special-key codepoints are not necessarily
+         * what you would expect. For example, <kbd>Esc</kbd> is the
+         * invalid Unicode character ``\uE00C``, not the ``\u001B`` Escape
+         * character from ASCII.
+         *
+         * This matches the behaviour of the
+         * `Send Keys
+         * <https://w3c.github.io/webdriver/#element-send-keys>`_
+         * WebDriver command.
+         *
+         * **Note:** If the element to be clicked does not have a
+         * unique ID, the document must not have any DOM mutations
+         * made between the function being called and the promise
+         * settling.
+         *
+         * @param {Element} element - element to send keys to
+         * @param {String} keys - keys to send to the element
+         * @returns {Promise} fulfilled after keys are sent, or rejected in
+         *                    the cases the WebDriver command errors
+         */
+        send_keys: function(element, keys) {
+            if (!inView(element)) {
+                element.scrollIntoView({behavior: "instant",
+                                        block: "end",
+                                        inline: "nearest"});
+            }
+
+            var pointerInteractablePaintTree = getPointerInteractablePaintTree(element);
+            if (pointerInteractablePaintTree.length === 0 ||
+                !element.contains(pointerInteractablePaintTree[0])) {
+                return Promise.reject(new Error("element send_keys intercepted error"));
+            }
+
+            return window.test_driver_internal.send_keys(element, keys);
+        },
+
+        /**
+         * Freeze the current page
+         *
+         * The freeze function transitions the page from the HIDDEN state to
+         * the FROZEN state as described in `Lifecycle API for Web Pages
+         * <https://github.com/WICG/page-lifecycle/blob/master/README.md>`_.
+         *
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the freeze request is sent, or rejected
+         *                    in case the WebDriver command errors
+         */
+        freeze: function(context=null) {
+            return window.test_driver_internal.freeze();
+        },
+
+        /**
+         * Minimizes the browser window.
+         *
+         * Matches the the behaviour of the `Minimize
+         * <https://www.w3.org/TR/webdriver/#minimize-window>`_
+         * WebDriver command
+         *
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled with the previous {@link
+         *                    https://www.w3.org/TR/webdriver/#dfn-windowrect-object|WindowRect}
+         *                      value, after the window is minimized.
+         */
+        minimize_window: function(context=null) {
+            return window.test_driver_internal.minimize_window(context);
+        },
+
+        /**
+         * Restore the window from minimized/maximized state to a given rect.
+         *
+         * Matches the behaviour of the `Set Window Rect
+         * <https://www.w3.org/TR/webdriver/#set-window-rect>`_
+         * WebDriver command
+         *
+         * @param {Object} rect - A {@link
+         *                           https://www.w3.org/TR/webdriver/#dfn-windowrect-object|WindowRect}
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the window is restored to the given rect.
+         */
+        set_window_rect: function(rect, context=null) {
+            return window.test_driver_internal.set_window_rect(rect, context);
+        },
+
+        /**
+         * Send a sequence of actions
+         *
+         * This function sends a sequence of actions to perform.
+         *
+         * Matches the behaviour of the `Actions
+         * <https://w3c.github.io/webdriver/#actions>`_ feature in
+         * WebDriver.
+         *
+         * Authors are encouraged to use the
+         * :js:class:`test_driver.Actions` builder rather than
+         * invoking this API directly.
+         *
+         * @param {Array} actions - an array of actions. The format is
+         *                          the same as the actions property
+         *                          of the `Perform Actions
+         *                          <https://w3c.github.io/webdriver/#perform-actions>`_
+         *                          WebDriver command. Each element is
+         *                          an object representing an input
+         *                          source and each input source
+         *                          itself has an actions property
+         *                          detailing the behaviour of that
+         *                          source at each timestep (or
+         *                          tick). Authors are not expected to
+         *                          construct the actions sequence by
+         *                          hand, but to use the builder api
+         *                          provided in testdriver-actions.js
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the actions are performed, or rejected in
+         *                    the cases the WebDriver command errors
+         */
+        action_sequence: function(actions, context=null) {
+            return window.test_driver_internal.action_sequence(actions, context);
+        },
+
+        /**
+         * Generates a test report on the current page
+         *
+         * The generate_test_report function generates a report (to be
+         * observed by ReportingObserver) for testing purposes.
+         *
+         * Matches the `Generate Test Report
+         * <https://w3c.github.io/reporting/#generate-test-report-command>`_
+         * WebDriver command.
+         *
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the report is generated, or
+         *                    rejected if the report generation fails
+         */
+        generate_test_report: function(message, context=null) {
+            return window.test_driver_internal.generate_test_report(message, context);
+        },
+
+        /**
+         * Sets the state of a permission
+         *
+         * This function simulates a user setting a permission into a
+         * particular state.
+         *
+         * Matches the `Set Permission
+         * <https://w3c.github.io/permissions/#set-permission-command>`_
+         * WebDriver command.
+         *
+         * @example
+         * await test_driver.set_permission({ name: "background-fetch" }, "denied");
+         * await test_driver.set_permission({ name: "push", userVisibleOnly: true }, "granted");
+         *
+         * @param {PermissionDescriptor} descriptor - a `PermissionDescriptor
+         *                              <https://w3c.github.io/permissions/#dom-permissiondescriptor>`_
+         *                              dictionary.
+         * @param {String} state - the state of the permission
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         * @returns {Promise} fulfilled after the permission is set, or rejected if setting the
+         *                    permission fails
+         */
+        set_permission: function(descriptor, state, context=null) {
+            let permission_params = {
+              descriptor,
+              state,
+            };
+            return window.test_driver_internal.set_permission(permission_params, context);
+        },
+
+        /**
+         * Creates a virtual authenticator
+         *
+         * This function creates a virtual authenticator for use with
+         * the U2F and WebAuthn APIs.
+         *
+         * Matches the `Add Virtual Authenticator
+         * <https://w3c.github.io/webauthn/#sctn-automation-add-virtual-authenticator>`_
+         * WebDriver command.
+         *
+         * @param {Object} config - an `Authenticator Configuration
+         *                          <https://w3c.github.io/webauthn/#authenticator-configuration>`_
+         *                          object
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the authenticator is added, or
+         *                    rejected in the cases the WebDriver command
+         *                    errors. Returns the ID of the authenticator
+         */
+        add_virtual_authenticator: function(config, context=null) {
+            return window.test_driver_internal.add_virtual_authenticator(config, context);
+        },
+
+        /**
+         * Removes a virtual authenticator
+         *
+         * This function removes a virtual authenticator that has been
+         * created by :js:func:`add_virtual_authenticator`.
+         *
+         * Matches the `Remove Virtual Authenticator
+         * <https://w3c.github.io/webauthn/#sctn-automation-remove-virtual-authenticator>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator to be
+         *                                    removed.
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the authenticator is removed, or
+         *                    rejected in the cases the WebDriver command
+         *                    errors
+         */
+        remove_virtual_authenticator: function(authenticator_id, context=null) {
+            return window.test_driver_internal.remove_virtual_authenticator(authenticator_id, context);
+        },
+
+        /**
+         * Adds a credential to a virtual authenticator
+         *
+         * Matches the `Add Credential
+         * <https://w3c.github.io/webauthn/#sctn-automation-add-credential>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator
+         * @param {Object} credential - A `Credential Parameters
+         *                              <https://w3c.github.io/webauthn/#credential-parameters>`_
+         *                              object
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the credential is added, or
+         *                    rejected in the cases the WebDriver command
+         *                    errors
+         */
+        add_credential: function(authenticator_id, credential, context=null) {
+            return window.test_driver_internal.add_credential(authenticator_id, credential, context);
+        },
+
+        /**
+         * Gets all the credentials stored in an authenticator
+         *
+         * This function retrieves all the credentials (added via the U2F API,
+         * WebAuthn, or the add_credential function) stored in a virtual
+         * authenticator
+         *
+         * Matches the `Get Credentials
+         * <https://w3c.github.io/webauthn/#sctn-automation-get-credentials>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the credentials are
+         *                    returned, or rejected in the cases the
+         *                    WebDriver command errors. Returns an
+         *                    array of `Credential Parameters
+         *                    <https://w3c.github.io/webauthn/#credential-parameters>`_
+         */
+        get_credentials: function(authenticator_id, context=null) {
+            return window.test_driver_internal.get_credentials(authenticator_id, context=null);
+        },
+
+        /**
+         * Remove a credential stored in an authenticator
+         *
+         * Matches the `Remove Credential
+         * <https://w3c.github.io/webauthn/#sctn-automation-remove-credential>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator
+         * @param {String} credential_id - the ID of the credential
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the credential is removed, or
+         *                    rejected in the cases the WebDriver command
+         *                    errors.
+         */
+        remove_credential: function(authenticator_id, credential_id, context=null) {
+            return window.test_driver_internal.remove_credential(authenticator_id, credential_id, context);
+        },
+
+        /**
+         * Removes all the credentials stored in a virtual authenticator
+         *
+         * Matches the `Remove All Credentials
+         * <https://w3c.github.io/webauthn/#sctn-automation-remove-all-credentials>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} fulfilled after the credentials are removed, or
+         *                    rejected in the cases the WebDriver command
+         *                    errors.
+         */
+        remove_all_credentials: function(authenticator_id, context=null) {
+            return window.test_driver_internal.remove_all_credentials(authenticator_id, context);
+        },
+
+        /**
+         * Sets the User Verified flag on an authenticator
+         *
+         * Sets whether requests requiring user verification will succeed or
+         * fail on a given virtual authenticator
+         *
+         * Matches the `Set User Verified
+         * <https://w3c.github.io/webauthn/#sctn-automation-set-user-verified>`_
+         * WebDriver command.
+         *
+         * @param {String} authenticator_id - the ID of the authenticator
+         * @param {boolean} uv - the User Verified flag
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         */
+        set_user_verified: function(authenticator_id, uv, context=null) {
+            return window.test_driver_internal.set_user_verified(authenticator_id, uv, context);
+        },
+
+        /**
+         * Sets the storage access rule for an origin when embedded
+         * in a third-party context.
+         *
+         * Matches the `Set Storage Access
+         * <https://privacycg.github.io/storage-access/#set-storage-access-command>`_
+         * WebDriver command.
+         *
+         * @param {String} origin - A third-party origin to block or allow.
+         *                          May be "*" to indicate all origins.
+         * @param {String} embedding_origin - an embedding (first-party) origin
+         *                                    on which {origin}'s access should
+         *                                    be blocked or allowed.
+         *                                    May be "*" to indicate all origins.
+         * @param {String} state - The storage access setting.
+         *                         Must be either "allowed" or "blocked".
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} Fulfilled after the storage access rule has been
+         *                    set, or rejected if setting the rule fails.
+         */
+        set_storage_access: function(origin, embedding_origin, state, context=null) {
+            if (state !== "allowed" && state !== "blocked") {
+                throw new Error("storage access status must be 'allowed' or 'blocked'");
+            }
+            const blocked = state === "blocked";
+            return window.test_driver_internal.set_storage_access(origin, embedding_origin, blocked, context);
+        },
+
+        /**
+         * Sets the current transaction automation mode for Secure Payment
+         * Confirmation.
+         *
+         * This function places `Secure Payment
+         * Confirmation <https://w3c.github.io/secure-payment-confirmation>`_ into
+         * an automated 'autoaccept' or 'autoreject' mode, to allow testing
+         * without user interaction with the transaction UX prompt.
+         *
+         * Matches the `Set SPC Transaction Mode
+         * <https://w3c.github.io/secure-payment-confirmation/#sctn-automation-set-spc-transaction-mode>`_
+         * WebDriver command.
+         *
+         * @example
+         * await test_driver.set_spc_transaction_mode("autoaccept");
+         * test.add_cleanup(() => {
+         *   return test_driver.set_spc_transaction_mode("none");
+         * });
+         *
+         * // Assumption: `request` is a PaymentRequest with a secure-payment-confirmation
+         * // payment method.
+         * const response = await request.show();
+         *
+         * @param {String} mode - The `transaction mode
+         *                        <https://w3c.github.io/secure-payment-confirmation/#enumdef-transactionautomationmode>`_
+         *                        to set. Must be one of "``none``",
+         *                        "``autoaccept``", or
+         *                        "``autoreject``".
+         * @param {WindowProxy} context - Browsing context in which
+         *                                to run the call, or null for the current
+         *                                browsing context.
+         *
+         * @returns {Promise} Fulfilled after the transaction mode has been set,
+         *                    or rejected if setting the mode fails.
+         */
+        set_spc_transaction_mode: function(mode, context=null) {
+          return window.test_driver_internal.set_spc_transaction_mode(mode, context);
+        },
+    };
+
+    window.test_driver_internal = {
+        /**
+         * This flag should be set to `true` by any code which implements the
+         * internal methods defined below for automation purposes. Doing so
+         * allows the library to signal failure immediately when an automated
+         * implementation of one of the methods is not available.
+         */
+        in_automation: false,
+
+        async click(element, coords) {
+            if (this.in_automation) {
+                throw new Error("click() is not implemented by testdriver-vendor.js");
+            }
+
+            return new Promise(function(resolve, reject) {
+                element.addEventListener("click", resolve);
+            });
+        },
+
+        async delete_all_cookies(context=null) {
+            throw new Error("delete_all_cookies() is not implemented by testdriver-vendor.js");
+        },
+
+        async get_all_cookies(context=null) {
+            throw new Error("get_all_cookies() is not implemented by testdriver-vendor.js");
+        },
+
+        async get_named_cookie(name, context=null) {
+            throw new Error("get_named_cookie() is not implemented by testdriver-vendor.js");
+        },
+
+        async send_keys(element, keys) {
+            if (this.in_automation) {
+                throw new Error("send_keys() is not implemented by testdriver-vendor.js");
+            }
+
+            return new Promise(function(resolve, reject) {
+                var seen = "";
+
+                function remove() {
+                    element.removeEventListener("keydown", onKeyDown);
+                }
+
+                function onKeyDown(event) {
+                    if (event.key.length > 1) {
+                        return;
+                    }
+
+                    seen += event.key;
+
+                    if (keys.indexOf(seen) !== 0) {
+                        reject(new Error("Unexpected key sequence: " + seen));
+                        remove();
+                    } else if (seen === keys) {
+                        resolve();
+                        remove();
+                    }
+                }
+
+                element.addEventListener("keydown", onKeyDown);
+            });
+        },
+
+        async freeze(context=null) {
+            throw new Error("freeze() is not implemented by testdriver-vendor.js");
+        },
+
+        async minimize_window(context=null) {
+            throw new Error("minimize_window() is not implemented by testdriver-vendor.js");
+        },
+
+        async set_window_rect(rect, context=null) {
+            throw new Error("set_window_rect() is not implemented by testdriver-vendor.js");
+        },
+
+        async action_sequence(actions, context=null) {
+            throw new Error("action_sequence() is not implemented by testdriver-vendor.js");
+        },
+
+        async generate_test_report(message, context=null) {
+            throw new Error("generate_test_report() is not implemented by testdriver-vendor.js");
+        },
+
+        async set_permission(permission_params, context=null) {
+            throw new Error("set_permission() is not implemented by testdriver-vendor.js");
+        },
+
+        async add_virtual_authenticator(config, context=null) {
+            throw new Error("add_virtual_authenticator() is not implemented by testdriver-vendor.js");
+        },
+
+        async remove_virtual_authenticator(authenticator_id, context=null) {
+            throw new Error("remove_virtual_authenticator() is not implemented by testdriver-vendor.js");
+        },
+
+        async add_credential(authenticator_id, credential, context=null) {
+            throw new Error("add_credential() is not implemented by testdriver-vendor.js");
+        },
+
+        async get_credentials(authenticator_id, context=null) {
+            throw new Error("get_credentials() is not implemented by testdriver-vendor.js");
+        },
+
+        async remove_credential(authenticator_id, credential_id, context=null) {
+            throw new Error("remove_credential() is not implemented by testdriver-vendor.js");
+        },
+
+        async remove_all_credentials(authenticator_id, context=null) {
+            throw new Error("remove_all_credentials() is not implemented by testdriver-vendor.js");
+        },
+
+        async set_user_verified(authenticator_id, uv, context=null) {
+            throw new Error("set_user_verified() is not implemented by testdriver-vendor.js");
+        },
+
+        async set_storage_access(origin, embedding_origin, blocked, context=null) {
+            throw new Error("set_storage_access() is not implemented by testdriver-vendor.js");
+        },
+
+        async set_spc_transaction_mode(mode, context=null) {
+            throw new Error("set_spc_transaction_mode() is not implemented by testdriver-vendor.js");
+        },
+
+    };
+})();
diff --git a/testing/web-platform/tests/resources/testdriver.js.headers b/testing/web-platform/tests/resources/testdriver.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/testdriver.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600
diff --git a/testing/web-platform/tests/resources/testharness.js b/testing/web-platform/tests/resources/testharness.js
new file mode 100644
index 0000000000..413993089b
--- /dev/null
+++ b/testing/web-platform/tests/resources/testharness.js
@@ -0,0 +1,4933 @@
+/*global self*/
+/*jshint latedef: nofunc*/
+
+/* Documentation: https://web-platform-tests.org/writing-tests/testharness-api.html
+ * (../docs/_writing-tests/testharness-api.md) */
+
+(function (global_scope)
+{
+    // default timeout is 10 seconds, test can override if needed
+    var settings = {
+        output:true,
+        harness_timeout:{
+            "normal":10000,
+            "long":60000
+        },
+        test_timeout:null,
+        message_events: ["start", "test_state", "result", "completion"],
+        debug: false,
+    };
+
+    var xhtml_ns = "http://www.w3.org/1999/xhtml";
+
+    /*
+     * TestEnvironment is an abstraction for the environment in which the test
+     * harness is used. Each implementation of a test environment has to provide
+     * the following interface:
+     *
+     * interface TestEnvironment {
+     *   // Invoked after the global 'tests' object has been created and it's
+     *   // safe to call add_*_callback() to register event handlers.
+     *   void on_tests_ready();
+     *
+     *   // Invoked after setup() has been called to notify the test environment
+     *   // of changes to the test harness properties.
+     *   void on_new_harness_properties(object properties);
+     *
+     *   // Should return a new unique default test name.
+     *   DOMString next_default_test_name();
+     *
+     *   // Should return the test harness timeout duration in milliseconds.
+     *   float test_timeout();
+     * };
+     */
+
+    /*
+     * A test environment with a DOM. The global object is 'window'. By default
+     * test results are displayed in a table. Any parent windows receive
+     * callbacks or messages via postMessage() when test events occur. See
+     * apisample11.html and apisample12.html.
+     */
+    function WindowTestEnvironment() {
+        this.name_counter = 0;
+        this.window_cache = null;
+        this.output_handler = null;
+        this.all_loaded = false;
+        var this_obj = this;
+        this.message_events = [];
+        this.dispatched_messages = [];
+
+        this.message_functions = {
+            start: [add_start_callback, remove_start_callback,
+                    function (properties) {
+                        this_obj._dispatch("start_callback", [properties],
+                                           {type: "start", properties: properties});
+                    }],
+
+            test_state: [add_test_state_callback, remove_test_state_callback,
+                         function(test) {
+                             this_obj._dispatch("test_state_callback", [test],
+                                                {type: "test_state",
+                                                 test: test.structured_clone()});
+                         }],
+            result: [add_result_callback, remove_result_callback,
+                     function (test) {
+                         this_obj.output_handler.show_status();
+                         this_obj._dispatch("result_callback", [test],
+                                            {type: "result",
+                                             test: test.structured_clone()});
+                     }],
+            completion: [add_completion_callback, remove_completion_callback,
+                         function (tests, harness_status, asserts) {
+                             var cloned_tests = map(tests, function(test) {
+                                 return test.structured_clone();
+                             });
+                             this_obj._dispatch("completion_callback", [tests, harness_status],
+                                                {type: "complete",
+                                                 tests: cloned_tests,
+                                                 status: harness_status.structured_clone(),
+                                                 asserts: asserts.map(assert => assert.structured_clone())});
+                         }]
+        }
+
+        on_event(window, 'load', function() {
+            this_obj.all_loaded = true;
+        });
+
+        on_event(window, 'message', function(event) {
+            if (event.data && event.data.type === "getmessages" && event.source) {
+                // A window can post "getmessages" to receive a duplicate of every
+                // message posted by this environment so far. This allows subscribers
+                // from fetch_tests_from_window to 'catch up' to the current state of
+                // this environment.
+                for (var i = 0; i < this_obj.dispatched_messages.length; ++i)
+                {
+                    event.source.postMessage(this_obj.dispatched_messages[i], "*");
+                }
+            }
+        });
+    }
+
+    WindowTestEnvironment.prototype._dispatch = function(selector, callback_args, message_arg) {
+        this.dispatched_messages.push(message_arg);
+        this._forEach_windows(
+                function(w, same_origin) {
+                    if (same_origin) {
+                        try {
+                            var has_selector = selector in w;
+                        } catch(e) {
+                            // If document.domain was set at some point same_origin can be
+                            // wrong and the above will fail.
+                            has_selector = false;
+                        }
+                        if (has_selector) {
+                            try {
+                                w[selector].apply(undefined, callback_args);
+                            } catch (e) {}
+                        }
+                    }
+                    if (w !== self) {
+                        w.postMessage(message_arg, "*");
+                    }
+                });
+    };
+
+    WindowTestEnvironment.prototype._forEach_windows = function(callback) {
+        // Iterate over the windows [self ... top, opener]. The callback is passed
+        // two objects, the first one is the window object itself, the second one
+        // is a boolean indicating whether or not it's on the same origin as the
+        // current window.
+        var cache = this.window_cache;
+        if (!cache) {
+            cache = [[self, true]];
+            var w = self;
+            var i = 0;
+            var so;
+            while (w != w.parent) {
+                w = w.parent;
+                so = is_same_origin(w);
+                cache.push([w, so]);
+                i++;
+            }
+            w = window.opener;
+            if (w) {
+                cache.push([w, is_same_origin(w)]);
+            }
+            this.window_cache = cache;
+        }
+
+        forEach(cache,
+                function(a) {
+                    callback.apply(null, a);
+                });
+    };
+
+    WindowTestEnvironment.prototype.on_tests_ready = function() {
+        var output = new Output();
+        this.output_handler = output;
+
+        var this_obj = this;
+
+        add_start_callback(function (properties) {
+            this_obj.output_handler.init(properties);
+        });
+
+        add_test_state_callback(function(test) {
+            this_obj.output_handler.show_status();
+        });
+
+        add_result_callback(function (test) {
+            this_obj.output_handler.show_status();
+        });
+
+        add_completion_callback(function (tests, harness_status, asserts_run) {
+            this_obj.output_handler.show_results(tests, harness_status, asserts_run);
+        });
+        this.setup_messages(settings.message_events);
+    };
+
+    WindowTestEnvironment.prototype.setup_messages = function(new_events) {
+        var this_obj = this;
+        forEach(settings.message_events, function(x) {
+            var current_dispatch = this_obj.message_events.indexOf(x) !== -1;
+            var new_dispatch = new_events.indexOf(x) !== -1;
+            if (!current_dispatch && new_dispatch) {
+                this_obj.message_functions[x][0](this_obj.message_functions[x][2]);
+            } else if (current_dispatch && !new_dispatch) {
+                this_obj.message_functions[x][1](this_obj.message_functions[x][2]);
+            }
+        });
+        this.message_events = new_events;
+    }
+
+    WindowTestEnvironment.prototype.next_default_test_name = function() {
+        var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
+        this.name_counter++;
+        return get_title() + suffix;
+    };
+
+    WindowTestEnvironment.prototype.on_new_harness_properties = function(properties) {
+        this.output_handler.setup(properties);
+        if (properties.hasOwnProperty("message_events")) {
+            this.setup_messages(properties.message_events);
+        }
+    };
+
+    WindowTestEnvironment.prototype.add_on_loaded_callback = function(callback) {
+        on_event(window, 'load', callback);
+    };
+
+    WindowTestEnvironment.prototype.test_timeout = function() {
+        var metas = document.getElementsByTagName("meta");
+        for (var i = 0; i < metas.length; i++) {
+            if (metas[i].name == "timeout") {
+                if (metas[i].content == "long") {
+                    return settings.harness_timeout.long;
+                }
+                break;
+            }
+        }
+        return settings.harness_timeout.normal;
+    };
+
+    /*
+     * Base TestEnvironment implementation for a generic web worker.
+     *
+     * Workers accumulate test results. One or more clients can connect and
+     * retrieve results from a worker at any time.
+     *
+     * WorkerTestEnvironment supports communicating with a client via a
+     * MessagePort.  The mechanism for determining the appropriate MessagePort
+     * for communicating with a client depends on the type of worker and is
+     * implemented by the various specializations of WorkerTestEnvironment
+     * below.
+     *
+     * A client document using testharness can use fetch_tests_from_worker() to
+     * retrieve results from a worker. See apisample16.html.
+     */
+    function WorkerTestEnvironment() {
+        this.name_counter = 0;
+        this.all_loaded = true;
+        this.message_list = [];
+        this.message_ports = [];
+    }
+
+    WorkerTestEnvironment.prototype._dispatch = function(message) {
+        this.message_list.push(message);
+        for (var i = 0; i < this.message_ports.length; ++i)
+        {
+            this.message_ports[i].postMessage(message);
+        }
+    };
+
+    // The only requirement is that port has a postMessage() method. It doesn't
+    // have to be an instance of a MessagePort, and often isn't.
+    WorkerTestEnvironment.prototype._add_message_port = function(port) {
+        this.message_ports.push(port);
+        for (var i = 0; i < this.message_list.length; ++i)
+        {
+            port.postMessage(this.message_list[i]);
+        }
+    };
+
+    WorkerTestEnvironment.prototype.next_default_test_name = function() {
+        var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
+        this.name_counter++;
+        return get_title() + suffix;
+    };
+
+    WorkerTestEnvironment.prototype.on_new_harness_properties = function() {};
+
+    WorkerTestEnvironment.prototype.on_tests_ready = function() {
+        var this_obj = this;
+        add_start_callback(
+                function(properties) {
+                    this_obj._dispatch({
+                        type: "start",
+                        properties: properties,
+                    });
+                });
+        add_test_state_callback(
+                function(test) {
+                    this_obj._dispatch({
+                        type: "test_state",
+                        test: test.structured_clone()
+                    });
+                });
+        add_result_callback(
+                function(test) {
+                    this_obj._dispatch({
+                        type: "result",
+                        test: test.structured_clone()
+                    });
+                });
+        add_completion_callback(
+                function(tests, harness_status, asserts) {
+                    this_obj._dispatch({
+                        type: "complete",
+                        tests: map(tests,
+                            function(test) {
+                                return test.structured_clone();
+                            }),
+                        status: harness_status.structured_clone(),
+                        asserts: asserts.map(assert => assert.structured_clone()),
+                    });
+                });
+    };
+
+    WorkerTestEnvironment.prototype.add_on_loaded_callback = function() {};
+
+    WorkerTestEnvironment.prototype.test_timeout = function() {
+        // Tests running in a worker don't have a default timeout. I.e. all
+        // worker tests behave as if settings.explicit_timeout is true.
+        return null;
+    };
+
+    /*
+     * Dedicated web workers.
+     * https://html.spec.whatwg.org/multipage/workers.html#dedicatedworkerglobalscope
+     *
+     * This class is used as the test_environment when testharness is running
+     * inside a dedicated worker.
+     */
+    function DedicatedWorkerTestEnvironment() {
+        WorkerTestEnvironment.call(this);
+        // self is an instance of DedicatedWorkerGlobalScope which exposes
+        // a postMessage() method for communicating via the message channel
+        // established when the worker is created.
+        this._add_message_port(self);
+    }
+    DedicatedWorkerTestEnvironment.prototype = Object.create(WorkerTestEnvironment.prototype);
+
+    DedicatedWorkerTestEnvironment.prototype.on_tests_ready = function() {
+        WorkerTestEnvironment.prototype.on_tests_ready.call(this);
+        // In the absence of an onload notification, we a require dedicated
+        // workers to explicitly signal when the tests are done.
+        tests.wait_for_finish = true;
+    };
+
+    /*
+     * Shared web workers.
+     * https://html.spec.whatwg.org/multipage/workers.html#sharedworkerglobalscope
+     *
+     * This class is used as the test_environment when testharness is running
+     * inside a shared web worker.
+     */
+    function SharedWorkerTestEnvironment() {
+        WorkerTestEnvironment.call(this);
+        var this_obj = this;
+        // Shared workers receive message ports via the 'onconnect' event for
+        // each connection.
+        self.addEventListener("connect",
+                function(message_event) {
+                    this_obj._add_message_port(message_event.source);
+                }, false);
+    }
+    SharedWorkerTestEnvironment.prototype = Object.create(WorkerTestEnvironment.prototype);
+
+    SharedWorkerTestEnvironment.prototype.on_tests_ready = function() {
+        WorkerTestEnvironment.prototype.on_tests_ready.call(this);
+        // In the absence of an onload notification, we a require shared
+        // workers to explicitly signal when the tests are done.
+        tests.wait_for_finish = true;
+    };
+
+    /*
+     * Service workers.
+     * http://www.w3.org/TR/service-workers/
+     *
+     * This class is used as the test_environment when testharness is running
+     * inside a service worker.
+     */
+    function ServiceWorkerTestEnvironment() {
+        WorkerTestEnvironment.call(this);
+        this.all_loaded = false;
+        this.on_loaded_callback = null;
+        var this_obj = this;
+        self.addEventListener("message",
+                function(event) {
+                    if (event.data && event.data.type && event.data.type === "connect") {
+                        this_obj._add_message_port(event.source);
+                    }
+                }, false);
+
+        // The oninstall event is received after the service worker script and
+        // all imported scripts have been fetched and executed. It's the
+        // equivalent of an onload event for a document. All tests should have
+        // been added by the time this event is received, thus it's not
+        // necessary to wait until the onactivate event. However, tests for
+        // installed service workers need another event which is equivalent to
+        // the onload event because oninstall is fired only on installation. The
+        // onmessage event is used for that purpose since tests using
+        // testharness.js should ask the result to its service worker by
+        // PostMessage. If the onmessage event is triggered on the service
+        // worker's context, that means the worker's script has been evaluated.
+        on_event(self, "install", on_all_loaded);
+        on_event(self, "message", on_all_loaded);
+        function on_all_loaded() {
+            if (this_obj.all_loaded)
+                return;
+            this_obj.all_loaded = true;
+            if (this_obj.on_loaded_callback) {
+              this_obj.on_loaded_callback();
+            }
+        }
+    }
+
+    ServiceWorkerTestEnvironment.prototype = Object.create(WorkerTestEnvironment.prototype);
+
+    ServiceWorkerTestEnvironment.prototype.add_on_loaded_callback = function(callback) {
+        if (this.all_loaded) {
+            callback();
+        } else {
+            this.on_loaded_callback = callback;
+        }
+    };
+
+    /*
+     * Shadow realms.
+     * https://github.com/tc39/proposal-shadowrealm
+     *
+     * This class is used as the test_environment when testharness is running
+     * inside a shadow realm.
+     */
+    function ShadowRealmTestEnvironment() {
+        WorkerTestEnvironment.call(this);
+        this.all_loaded = false;
+        this.on_loaded_callback = null;
+    }
+
+    ShadowRealmTestEnvironment.prototype = Object.create(WorkerTestEnvironment.prototype);
+
+    /**
+     * Signal to the test environment that the tests are ready and the on-loaded
+     * callback should be run.
+     *
+     * Shadow realms are not *really* a DOM context: they have no `onload` or similar
+     * event for us to use to set up the test environment; so, instead, this method
+     * is manually triggered from the incubating realm
+     *
+     * @param {Function} message_destination - a function that receives JSON-serializable
+     * data to send to the incubating realm, in the same format as used by RemoteContext
+     */
+    ShadowRealmTestEnvironment.prototype.begin = function(message_destination) {
+        if (this.all_loaded) {
+            throw new Error("Tried to start a shadow realm test environment after it has already started");
+        }
+        var fakeMessagePort = {};
+        fakeMessagePort.postMessage = message_destination;
+        this._add_message_port(fakeMessagePort);
+        this.all_loaded = true;
+        if (this.on_loaded_callback) {
+            this.on_loaded_callback();
+        }
+    };
+
+    ShadowRealmTestEnvironment.prototype.add_on_loaded_callback = function(callback) {
+        if (this.all_loaded) {
+            callback();
+        } else {
+            this.on_loaded_callback = callback;
+        }
+    };
+
+    /*
+     * JavaScript shells.
+     *
+     * This class is used as the test_environment when testharness is running
+     * inside a JavaScript shell.
+     */
+    function ShellTestEnvironment() {
+        this.name_counter = 0;
+        this.all_loaded = false;
+        this.on_loaded_callback = null;
+        Promise.resolve().then(function() {
+            this.all_loaded = true
+            if (this.on_loaded_callback) {
+                this.on_loaded_callback();
+            }
+        }.bind(this));
+        this.message_list = [];
+        this.message_ports = [];
+    }
+
+    ShellTestEnvironment.prototype.next_default_test_name = function() {
+        var suffix = this.name_counter > 0 ? " " + this.name_counter : "";
+        this.name_counter++;
+        return get_title() + suffix;
+    };
+
+    ShellTestEnvironment.prototype.on_new_harness_properties = function() {};
+
+    ShellTestEnvironment.prototype.on_tests_ready = function() {};
+
+    ShellTestEnvironment.prototype.add_on_loaded_callback = function(callback) {
+        if (this.all_loaded) {
+            callback();
+        } else {
+            this.on_loaded_callback = callback;
+        }
+    };
+
+    ShellTestEnvironment.prototype.test_timeout = function() {
+        // Tests running in a shell don't have a default timeout, so behave as
+        // if settings.explicit_timeout is true.
+        return null;
+    };
+
+    function create_test_environment() {
+        if ('document' in global_scope) {
+            return new WindowTestEnvironment();
+        }
+        if ('DedicatedWorkerGlobalScope' in global_scope &&
+            global_scope instanceof DedicatedWorkerGlobalScope) {
+            return new DedicatedWorkerTestEnvironment();
+        }
+        if ('SharedWorkerGlobalScope' in global_scope &&
+            global_scope instanceof SharedWorkerGlobalScope) {
+            return new SharedWorkerTestEnvironment();
+        }
+        if ('ServiceWorkerGlobalScope' in global_scope &&
+            global_scope instanceof ServiceWorkerGlobalScope) {
+            return new ServiceWorkerTestEnvironment();
+        }
+        if ('WorkerGlobalScope' in global_scope &&
+            global_scope instanceof WorkerGlobalScope) {
+            return new DedicatedWorkerTestEnvironment();
+        }
+        /* Shadow realm global objects are _ordinary_ objects (i.e. their prototype is
+         * Object) so we don't have a nice `instanceof` test to use; instead, we
+         * check if the there is a GLOBAL.isShadowRealm() property
+         * on the global object. that was set by the test harness when it
+         * created the ShadowRealm.
+         */
+        if (global_scope.GLOBAL && global_scope.GLOBAL.isShadowRealm()) {
+            return new ShadowRealmTestEnvironment();
+        }
+
+        return new ShellTestEnvironment();
+    }
+
+    var test_environment = create_test_environment();
+
+    function is_shared_worker(worker) {
+        return 'SharedWorker' in global_scope && worker instanceof SharedWorker;
+    }
+
+    function is_service_worker(worker) {
+        // The worker object may be from another execution context,
+        // so do not use instanceof here.
+        return 'ServiceWorker' in global_scope &&
+            Object.prototype.toString.call(worker) == '[object ServiceWorker]';
+    }
+
+    var seen_func_name = Object.create(null);
+
+    function get_test_name(func, name)
+    {
+        if (name) {
+            return name;
+        }
+
+        if (func) {
+            var func_code = func.toString();
+
+            // Try and match with brackets, but fallback to matching without
+            var arrow = func_code.match(/^\(\)\s*=>\s*(?:{(.*)}\s*|(.*))$/);
+
+            // Check for JS line separators
+            if (arrow !== null && !/[\u000A\u000D\u2028\u2029]/.test(func_code)) {
+                var trimmed = (arrow[1] !== undefined ? arrow[1] : arrow[2]).trim();
+                // drop trailing ; if there's no earlier ones
+                trimmed = trimmed.replace(/^([^;]*)(;\s*)+$/, "$1");
+
+                if (trimmed) {
+                    let name = trimmed;
+                    if (seen_func_name[trimmed]) {
+                        // This subtest name already exists, so add a suffix.
+                        name += " " + seen_func_name[trimmed];
+                    } else {
+                        seen_func_name[trimmed] = 0;
+                    }
+                    seen_func_name[trimmed] += 1;
+                    return name;
+                }
+            }
+        }
+
+        return test_environment.next_default_test_name();
+    }
+
+    /**
+     * @callback TestFunction
+     * @param {Test} test - The test currnetly being run.
+     * @param {Any[]} args - Additional args to pass to function.
+     *
+     */
+
+    /**
+     * Create a synchronous test
+     *
+     * @param {TestFunction} func - Test function. This is executed
+     * immediately. If it returns without error, the test status is
+     * set to ``PASS``. If it throws an :js:class:`AssertionError`, or
+     * any other exception, the test status is set to ``FAIL``
+     * (typically from an `assert` function).
+     * @param {String} name - Test name. This must be unique in a
+     * given file and must be invariant between runs.
+     */
+    function test(func, name, properties)
+    {
+        if (tests.promise_setup_called) {
+            tests.status.status = tests.status.ERROR;
+            tests.status.message = '`test` invoked after `promise_setup`';
+            tests.complete();
+        }
+        var test_name = get_test_name(func, name);
+        var test_obj = new Test(test_name, properties);
+        var value = test_obj.step(func, test_obj, test_obj);
+
+        if (value !== undefined) {
+            var msg = 'Test named "' + test_name +
+                '" passed a function to `test` that returned a value.';
+
+            try {
+                if (value && typeof value.then === 'function') {
+                    msg += ' Consider using `promise_test` instead when ' +
+                        'using Promises or async/await.';
+                }
+            } catch (err) {}
+
+            tests.status.status = tests.status.ERROR;
+            tests.status.message = msg;
+        }
+
+        if (test_obj.phase === test_obj.phases.STARTED) {
+            test_obj.done();
+        }
+    }
+
+    /**
+     * Create an asynchronous test
+     *
+     * @param {TestFunction|string} funcOrName - Initial step function
+     * to call immediately with the test name as an argument (if any),
+     * or name of the test.
+     * @param {String} name - Test name (if a test function was
+     * provided). This must be unique in a given file and must be
+     * invariant between runs.
+     * @returns {Test} An object representing the ongoing test.
+     */
+    function async_test(func, name, properties)
+    {
+        if (tests.promise_setup_called) {
+            tests.status.status = tests.status.ERROR;
+            tests.status.message = '`async_test` invoked after `promise_setup`';
+            tests.complete();
+        }
+        if (typeof func !== "function") {
+            properties = name;
+            name = func;
+            func = null;
+        }
+        var test_name = get_test_name(func, name);
+        var test_obj = new Test(test_name, properties);
+        if (func) {
+            var value = test_obj.step(func, test_obj, test_obj);
+
+            // Test authors sometimes return values to async_test, expecting us
+            // to handle the value somehow. Make doing so a harness error to be
+            // clear this is invalid, and point authors to promise_test if it
+            // may be appropriate.
+            //
+            // Note that we only perform this check on the initial function
+            // passed to async_test, not on any later steps - we haven't seen a
+            // consistent problem with those (and it's harder to check).
+            if (value !== undefined) {
+                var msg = 'Test named "' + test_name +
+                    '" passed a function to `async_test` that returned a value.';
+
+                try {
+                    if (value && typeof value.then === 'function') {
+                        msg += ' Consider using `promise_test` instead when ' +
+                            'using Promises or async/await.';
+                    }
+                } catch (err) {}
+
+                tests.set_status(tests.status.ERROR, msg);
+                tests.complete();
+            }
+        }
+        return test_obj;
+    }
+
+    /**
+     * Create a promise test.
+     *
+     * Promise tests are tests which are represented by a promise
+     * object. If the promise is fulfilled the test passes, if it's
+     * rejected the test fails, otherwise the test passes.
+     *
+     * @param {TestFunction} func - Test function. This must return a
+     * promise. The test is automatically marked as complete once the
+     * promise settles.
+     * @param {String} name - Test name. This must be unique in a
+     * given file and must be invariant between runs.
+     */
+    function promise_test(func, name, properties) {
+        if (typeof func !== "function") {
+            properties = name;
+            name = func;
+            func = null;
+        }
+        var test_name = get_test_name(func, name);
+        var test = new Test(test_name, properties);
+        test._is_promise_test = true;
+
+        // If there is no promise tests queue make one.
+        if (!tests.promise_tests) {
+            tests.promise_tests = Promise.resolve();
+        }
+        tests.promise_tests = tests.promise_tests.then(function() {
+            return new Promise(function(resolve) {
+                var promise = test.step(func, test, test);
+
+                test.step(function() {
+                    assert(!!promise, "promise_test", null,
+                           "test body must return a 'thenable' object (received ${value})",
+                           {value:promise});
+                    assert(typeof promise.then === "function", "promise_test", null,
+                           "test body must return a 'thenable' object (received an object with no `then` method)",
+                           null);
+                });
+
+                // Test authors may use the `step` method within a
+                // `promise_test` even though this reflects a mixture of
+                // asynchronous control flow paradigms. The "done" callback
+                // should be registered prior to the resolution of the
+                // user-provided Promise to avoid timeouts in cases where the
+                // Promise does not settle but a `step` function has thrown an
+                // error.
+                add_test_done_callback(test, resolve);
+
+                Promise.resolve(promise)
+                    .catch(test.step_func(
+                        function(value) {
+                            if (value instanceof AssertionError) {
+                                throw value;
+                            }
+                            assert(false, "promise_test", null,
+                                   "Unhandled rejection with value: ${value}", {value:value});
+                        }))
+                    .then(function() {
+                        test.done();
+                    });
+                });
+        });
+    }
+
+    /**
+     * Make a copy of a Promise in the current realm.
+     *
+     * @param {Promise} promise the given promise that may be from a different
+     *                          realm
+     * @returns {Promise}
+     *
+     * An arbitrary promise provided by the caller may have originated
+     * in another frame that have since navigated away, rendering the
+     * frame's document inactive. Such a promise cannot be used with
+     * `await` or Promise.resolve(), as microtasks associated with it
+     * may be prevented from being run. See `issue
+     * 5319<https://github.com/whatwg/html/issues/5319>`_ for a
+     * particular case.
+     *
+     * In functions we define here, there is an expectation from the caller
+     * that the promise is from the current realm, that can always be used with
+     * `await`, etc. We therefore create a new promise in this realm that
+     * inherit the value and status from the given promise.
+     */
+
+    function bring_promise_to_current_realm(promise) {
+        return new Promise(promise.then.bind(promise));
+    }
+
+    /**
+     * Assert that a Promise is rejected with the right ECMAScript exception.
+     *
+     * @param {Test} test - the `Test` to use for the assertion.
+     * @param {Function} constructor - The expected exception constructor.
+     * @param {Promise} promise - The promise that's expected to
+     * reject with the given exception.
+     * @param {string} [description] Error message to add to assert in case of
+     *                               failure.
+     */
+    function promise_rejects_js(test, constructor, promise, description) {
+        return bring_promise_to_current_realm(promise)
+            .then(test.unreached_func("Should have rejected: " + description))
+            .catch(function(e) {
+                assert_throws_js_impl(constructor, function() { throw e },
+                                      description, "promise_rejects_js");
+            });
+    }
+
+    /**
+     * Assert that a Promise is rejected with the right DOMException.
+     *
+     * For the remaining arguments, there are two ways of calling
+     * promise_rejects_dom:
+     *
+     * 1) If the DOMException is expected to come from the current global, the
+     * third argument should be the promise expected to reject, and a fourth,
+     * optional, argument is the assertion description.
+     *
+     * 2) If the DOMException is expected to come from some other global, the
+     * third argument should be the DOMException constructor from that global,
+     * the fourth argument the promise expected to reject, and the fifth,
+     * optional, argument the assertion description.
+     *
+     * @param {Test} test - the `Test` to use for the assertion.
+     * @param {number|string} type - See documentation for
+     * `assert_throws_dom <#assert_throws_dom>`_.
+     * @param {Function} promiseOrConstructor - Either the constructor
+     * for the expected exception (if the exception comes from another
+     * global), or the promise that's expected to reject (if the
+     * exception comes from the current global).
+     * @param {Function|string} descriptionOrPromise - Either the
+     * promise that's expected to reject (if the exception comes from
+     * another global), or the optional description of the condition
+     * being tested (if the exception comes from the current global).
+     * @param {string} [description] - Description of the condition
+     * being tested (if the exception comes from another global).
+     *
+     */
+    function promise_rejects_dom(test, type, promiseOrConstructor, descriptionOrPromise, maybeDescription) {
+        let constructor, promise, description;
+        if (typeof promiseOrConstructor === "function" &&
+            promiseOrConstructor.name === "DOMException") {
+            constructor = promiseOrConstructor;
+            promise = descriptionOrPromise;
+            description = maybeDescription;
+        } else {
+            constructor = self.DOMException;
+            promise = promiseOrConstructor;
+            description = descriptionOrPromise;
+            assert(maybeDescription === undefined,
+                   "Too many args pased to no-constructor version of promise_rejects_dom");
+        }
+        return bring_promise_to_current_realm(promise)
+            .then(test.unreached_func("Should have rejected: " + description))
+            .catch(function(e) {
+                assert_throws_dom_impl(type, function() { throw e }, description,
+                                       "promise_rejects_dom", constructor);
+            });
+    }
+
+    /**
+     * Assert that a Promise is rejected with the provided value.
+     *
+     * @param {Test} test - the `Test` to use for the assertion.
+     * @param {Any} exception - The expected value of the rejected promise.
+     * @param {Promise} promise - The promise that's expected to
+     * reject.
+     * @param {string} [description] Error message to add to assert in case of
+     *                               failure.
+     */
+    function promise_rejects_exactly(test, exception, promise, description) {
+        return bring_promise_to_current_realm(promise)
+            .then(test.unreached_func("Should have rejected: " + description))
+            .catch(function(e) {
+                assert_throws_exactly_impl(exception, function() { throw e },
+                                           description, "promise_rejects_exactly");
+            });
+    }
+
+    /**
+     * Allow DOM events to be handled using Promises.
+     *
+     * This can make it a lot easier to test a very specific series of events,
+     * including ensuring that unexpected events are not fired at any point.
+     *
+     * `EventWatcher` will assert if an event occurs while there is no `wait_for`
+     * created Promise waiting to be fulfilled, or if the event is of a different type
+     * to the type currently expected. This ensures that only the events that are
+     * expected occur, in the correct order, and with the correct timing.
+     *
+     * @constructor
+     * @param {Test} test - The `Test` to use for the assertion.
+     * @param {EventTarget} watchedNode - The target expected to receive the events.
+     * @param {string[]} eventTypes - List of events to watch for.
+     * @param {Promise} timeoutPromise - Promise that will cause the
+     * test to be set to `TIMEOUT` once fulfilled.
+     *
+     */
+    function EventWatcher(test, watchedNode, eventTypes, timeoutPromise)
+    {
+        if (typeof eventTypes == 'string') {
+            eventTypes = [eventTypes];
+        }
+
+        var waitingFor = null;
+
+        // This is null unless we are recording all events, in which case it
+        // will be an Array object.
+        var recordedEvents = null;
+
+        var eventHandler = test.step_func(function(evt) {
+            assert_true(!!waitingFor,
+                        'Not expecting event, but got ' + evt.type + ' event');
+            assert_equals(evt.type, waitingFor.types[0],
+                          'Expected ' + waitingFor.types[0] + ' event, but got ' +
+                          evt.type + ' event instead');
+
+            if (Array.isArray(recordedEvents)) {
+                recordedEvents.push(evt);
+            }
+
+            if (waitingFor.types.length > 1) {
+                // Pop first event from array
+                waitingFor.types.shift();
+                return;
+            }
+            // We need to null out waitingFor before calling the resolve function
+            // since the Promise's resolve handlers may call wait_for() which will
+            // need to set waitingFor.
+            var resolveFunc = waitingFor.resolve;
+            waitingFor = null;
+            // Likewise, we should reset the state of recordedEvents.
+            var result = recordedEvents || evt;
+            recordedEvents = null;
+            resolveFunc(result);
+        });
+
+        for (var i = 0; i < eventTypes.length; i++) {
+            watchedNode.addEventListener(eventTypes[i], eventHandler, false);
+        }
+
+        /**
+         * Returns a Promise that will resolve after the specified event or
+         * series of events has occurred.
+         *
+         * @param {Object} options An optional options object. If the 'record' property
+         *                 on this object has the value 'all', when the Promise
+         *                 returned by this function is resolved,  *all* Event
+         *                 objects that were waited for will be returned as an
+         *                 array.
+         *
+         * @example
+         * const watcher = new EventWatcher(t, div, [ 'animationstart',
+         *                                            'animationiteration',
+         *                                            'animationend' ]);
+         * return watcher.wait_for([ 'animationstart', 'animationend' ],
+         *                         { record: 'all' }).then(evts => {
+         *   assert_equals(evts[0].elapsedTime, 0.0);
+         *   assert_equals(evts[1].elapsedTime, 2.0);
+         * });
+         */
+        this.wait_for = function(types, options) {
+            if (waitingFor) {
+                return Promise.reject('Already waiting for an event or events');
+            }
+            if (typeof types == 'string') {
+                types = [types];
+            }
+            if (options && options.record && options.record === 'all') {
+                recordedEvents = [];
+            }
+            return new Promise(function(resolve, reject) {
+                var timeout = test.step_func(function() {
+                    // If the timeout fires after the events have been received
+                    // or during a subsequent call to wait_for, ignore it.
+                    if (!waitingFor || waitingFor.resolve !== resolve)
+                        return;
+
+                    // This should always fail, otherwise we should have
+                    // resolved the promise.
+                    assert_true(waitingFor.types.length == 0,
+                                'Timed out waiting for ' + waitingFor.types.join(', '));
+                    var result = recordedEvents;
+                    recordedEvents = null;
+                    var resolveFunc = waitingFor.resolve;
+                    waitingFor = null;
+                    resolveFunc(result);
+                });
+
+                if (timeoutPromise) {
+                    timeoutPromise().then(timeout);
+                }
+
+                waitingFor = {
+                    types: types,
+                    resolve: resolve,
+                    reject: reject
+                };
+            });
+        };
+
+        /**
+         * Stop listening for events
+         */
+        function stop_watching() {
+            for (var i = 0; i < eventTypes.length; i++) {
+                watchedNode.removeEventListener(eventTypes[i], eventHandler, false);
+            }
+        };
+
+        test._add_cleanup(stop_watching);
+
+        return this;
+    }
+    expose(EventWatcher, 'EventWatcher');
+
+    /**
+     * @typedef {Object} SettingsObject
+     * @property {bool} single_test - Use the single-page-test
+     * mode. In this mode the Document represents a single
+     * `async_test`. Asserts may be used directly without requiring
+     * `Test.step` or similar wrappers, and any exceptions set the
+     * status of the test rather than the status of the harness.
+     * @property {bool} allow_uncaught_exception - don't treat an
+     * uncaught exception as an error; needed when e.g. testing the
+     * `window.onerror` handler.
+     * @property {boolean} explicit_done - Wait for a call to `done()`
+     * before declaring all tests complete (this is always true for
+     * single-page tests).
+     * @property hide_test_state - hide the test state output while
+     * the test is running; This is helpful when the output of the test state
+     * may interfere the test results.
+     * @property {bool} explicit_timeout - disable file timeout; only
+     * stop waiting for results when the `timeout()` function is
+     * called This should typically only be set for manual tests, or
+     * by a test runner that providees its own timeout mechanism.
+     * @property {number} timeout_multiplier - Multiplier to apply to
+     * per-test timeouts. This should only be set by a test runner.
+     * @property {Document} output_document - The document to which
+     * results should be logged. By default this is the current
+     * document but could be an ancestor document in some cases e.g. a
+     * SVG test loaded in an HTML wrapper
+     *
+     */
+
+    /**
+     * Configure the harness
+     *
+     * @param {Function|SettingsObject} funcOrProperties - Either a
+     * setup function to run, or a set of properties. If this is a
+     * function that function is run synchronously. Any exception in
+     * the function will set the overall harness status to `ERROR`.
+     * @param {SettingsObject} maybeProperties - An object containing
+     * the settings to use, if the first argument is a function.
+     *
+     */
+    function setup(func_or_properties, maybe_properties)
+    {
+        var func = null;
+        var properties = {};
+        if (arguments.length === 2) {
+            func = func_or_properties;
+            properties = maybe_properties;
+        } else if (func_or_properties instanceof Function) {
+            func = func_or_properties;
+        } else {
+            properties = func_or_properties;
+        }
+        tests.setup(func, properties);
+        test_environment.on_new_harness_properties(properties);
+    }
+
+    /**
+     * Configure the harness, waiting for a promise to resolve
+     * before running any `promise_test` tests.
+     *
+     * @param {Function} func - Function returning a promise that's
+     * run synchronously. Promise tests are not run until after this
+     * function has resolved.
+     * @param {SettingsObject} [properties] - An object containing
+     * the harness settings to use.
+     *
+     */
+    function promise_setup(func, properties={})
+    {
+        if (typeof func !== "function") {
+            tests.set_status(tests.status.ERROR,
+                             "promise_test invoked without a function");
+            tests.complete();
+            return;
+        }
+        tests.promise_setup_called = true;
+
+        if (!tests.promise_tests) {
+            tests.promise_tests = Promise.resolve();
+        }
+
+        tests.promise_tests = tests.promise_tests
+            .then(function()
+                  {
+                      var result;
+
+                      tests.setup(null, properties);
+                      result = func();
+                      test_environment.on_new_harness_properties(properties);
+
+                      if (!result || typeof result.then !== "function") {
+                          throw "Non-thenable returned by function passed to `promise_setup`";
+                      }
+                      return result;
+                  })
+            .catch(function(e)
+                   {
+                       tests.set_status(tests.status.ERROR,
+                                        String(e),
+                                        e && e.stack);
+                       tests.complete();
+                   });
+    }
+
+    /**
+     * Mark test loading as complete.
+     *
+     * Typically this function is called implicitly on page load; it's
+     * only necessary for users to call this when either the
+     * ``explicit_done`` or ``single_page`` properties have been set
+     * via the :js:func:`setup` function.
+     *
+     * For single page tests this marks the test as complete and sets its status.
+     * For other tests, this marks test loading as complete, but doesn't affect ongoing tests.
+     */
+    function done() {
+        if (tests.tests.length === 0) {
+            // `done` is invoked after handling uncaught exceptions, so if the
+            // harness status is already set, the corresponding message is more
+            // descriptive than the generic message defined here.
+            if (tests.status.status === null) {
+                tests.status.status = tests.status.ERROR;
+                tests.status.message = "done() was called without first defining any tests";
+            }
+
+            tests.complete();
+            return;
+        }
+        if (tests.file_is_test) {
+            // file is test files never have asynchronous cleanup logic,
+            // meaning the fully-synchronous `done` function can be used here.
+            tests.tests[0].done();
+        }
+        tests.end_wait();
+    }
+
+    /**
+     * @deprecated generate a list of tests from a function and list of arguments
+     *
+     * This is deprecated because it runs all the tests outside of the test functions
+     * and as a result any test throwing an exception will result in no tests being
+     * run. In almost all cases, you should simply call test within the loop you would
+     * use to generate the parameter list array.
+     *
+     * @param {Function} func - The function that will be called for each generated tests.
+     * @param {Any[][]} args - An array of arrays. Each nested array
+     * has the structure `[testName, ...testArgs]`. For each of these nested arrays
+     * array, a test is generated with name `testName` and test function equivalent to
+     * `func(..testArgs)`.
+     */
+    function generate_tests(func, args, properties) {
+        forEach(args, function(x, i)
+                {
+                    var name = x[0];
+                    test(function()
+                         {
+                             func.apply(this, x.slice(1));
+                         },
+                         name,
+                         Array.isArray(properties) ? properties[i] : properties);
+                });
+    }
+
+    /**
+     * @deprecated
+     *
+     * Register a function as a DOM event listener to the
+     * given object for the event bubbling phase.
+     *
+     * @param {EventTarget} object - Event target
+     * @param {string} event - Event name
+     * @param {Function} callback - Event handler.
+     */
+    function on_event(object, event, callback)
+    {
+        object.addEventListener(event, callback, false);
+    }
+
+    /**
+     * Global version of :js:func:`Test.step_timeout` for use in single page tests.
+     *
+     * @param {Function} func - Function to run after the timeout
+     * @param {number} timeout - Time in ms to wait before running the
+     * test step. The actual wait time is ``timeout`` x
+     * ``timeout_multiplier``.
+     */
+    function step_timeout(func, timeout) {
+        var outer_this = this;
+        var args = Array.prototype.slice.call(arguments, 2);
+        return setTimeout(function() {
+            func.apply(outer_this, args);
+        }, timeout * tests.timeout_multiplier);
+    }
+
+    expose(test, 'test');
+    expose(async_test, 'async_test');
+    expose(promise_test, 'promise_test');
+    expose(promise_rejects_js, 'promise_rejects_js');
+    expose(promise_rejects_dom, 'promise_rejects_dom');
+    expose(promise_rejects_exactly, 'promise_rejects_exactly');
+    expose(generate_tests, 'generate_tests');
+    expose(setup, 'setup');
+    expose(promise_setup, 'promise_setup');
+    expose(done, 'done');
+    expose(on_event, 'on_event');
+    expose(step_timeout, 'step_timeout');
+
+    /*
+     * Return a string truncated to the given length, with ... added at the end
+     * if it was longer.
+     */
+    function truncate(s, len)
+    {
+        if (s.length > len) {
+            return s.substring(0, len - 3) + "...";
+        }
+        return s;
+    }
+
+    /*
+     * Return true if object is probably a Node object.
+     */
+    function is_node(object)
+    {
+        // I use duck-typing instead of instanceof, because
+        // instanceof doesn't work if the node is from another window (like an
+        // iframe's contentWindow):
+        // http://www.w3.org/Bugs/Public/show_bug.cgi?id=12295
+        try {
+            var has_node_properties = ("nodeType" in object &&
+                                       "nodeName" in object &&
+                                       "nodeValue" in object &&
+                                       "childNodes" in object);
+        } catch (e) {
+            // We're probably cross-origin, which means we aren't a node
+            return false;
+        }
+
+        if (has_node_properties) {
+            try {
+                object.nodeType;
+            } catch (e) {
+                // The object is probably Node.prototype or another prototype
+                // object that inherits from it, and not a Node instance.
+                return false;
+            }
+            return true;
+        }
+        return false;
+    }
+
+    var replacements = {
+        "0": "0",
+        "1": "x01",
+        "2": "x02",
+        "3": "x03",
+        "4": "x04",
+        "5": "x05",
+        "6": "x06",
+        "7": "x07",
+        "8": "b",
+        "9": "t",
+        "10": "n",
+        "11": "v",
+        "12": "f",
+        "13": "r",
+        "14": "x0e",
+        "15": "x0f",
+        "16": "x10",
+        "17": "x11",
+        "18": "x12",
+        "19": "x13",
+        "20": "x14",
+        "21": "x15",
+        "22": "x16",
+        "23": "x17",
+        "24": "x18",
+        "25": "x19",
+        "26": "x1a",
+        "27": "x1b",
+        "28": "x1c",
+        "29": "x1d",
+        "30": "x1e",
+        "31": "x1f",
+        "0xfffd": "ufffd",
+        "0xfffe": "ufffe",
+        "0xffff": "uffff",
+    };
+
+    /**
+     * Convert a value to a nice, human-readable string
+     *
+     * When many JavaScript Object values are coerced to a String, the
+     * resulting value will be ``"[object Object]"``. This obscures
+     * helpful information, making the coerced value unsuitable for
+     * use in assertion messages, test names, and debugging
+     * statements. `format_value` produces more distinctive string
+     * representations of many kinds of objects, including arrays and
+     * the more important DOM Node types. It also translates String
+     * values containing control characters to include human-readable
+     * representations.
+     *
+     * @example
+     * // "Document node with 2 children"
+     * format_value(document);
+     * @example
+     * // "\"foo\\uffffbar\""
+     * format_value("foo\uffffbar");
+     * @example
+     * // "[-0, Infinity]"
+     * format_value([-0, Infinity]);
+     * @param {Any} val - The value to convert to a string.
+     * @returns {string} - A string representation of ``val``, optimised for human readability.
+     */
+    function format_value(val, seen)
+    {
+        if (!seen) {
+            seen = [];
+        }
+        if (typeof val === "object" && val !== null) {
+            if (seen.indexOf(val) >= 0) {
+                return "[...]";
+            }
+            seen.push(val);
+        }
+        if (Array.isArray(val)) {
+            let output = "[";
+            if (val.beginEllipsis !== undefined) {
+                output += "…, ";
+            }
+            output += val.map(function(x) {return format_value(x, seen);}).join(", ");
+            if (val.endEllipsis !== undefined) {
+                output += ", …";
+            }
+            return output + "]";
+        }
+
+        switch (typeof val) {
+        case "string":
+            val = val.replace(/\\/g, "\\\\");
+            for (var p in replacements) {
+                var replace = "\\" + replacements[p];
+                val = val.replace(RegExp(String.fromCharCode(p), "g"), replace);
+            }
+            return '"' + val.replace(/"/g, '\\"') + '"';
+        case "boolean":
+        case "undefined":
+            return String(val);
+        case "number":
+            // In JavaScript, -0 === 0 and String(-0) == "0", so we have to
+            // special-case.
+            if (val === -0 && 1/val === -Infinity) {
+                return "-0";
+            }
+            return String(val);
+        case "object":
+            if (val === null) {
+                return "null";
+            }
+
+            // Special-case Node objects, since those come up a lot in my tests.  I
+            // ignore namespaces.
+            if (is_node(val)) {
+                switch (val.nodeType) {
+                case Node.ELEMENT_NODE:
+                    var ret = "<" + val.localName;
+                    for (var i = 0; i < val.attributes.length; i++) {
+                        ret += " " + val.attributes[i].name + '="' + val.attributes[i].value + '"';
+                    }
+                    ret += ">" + val.innerHTML + "</" + val.localName + ">";
+                    return "Element node " + truncate(ret, 60);
+                case Node.TEXT_NODE:
+                    return 'Text node "' + truncate(val.data, 60) + '"';
+                case Node.PROCESSING_INSTRUCTION_NODE:
+                    return "ProcessingInstruction node with target " + format_value(truncate(val.target, 60)) + " and data " + format_value(truncate(val.data, 60));
+                case Node.COMMENT_NODE:
+                    return "Comment node <!--" + truncate(val.data, 60) + "-->";
+                case Node.DOCUMENT_NODE:
+                    return "Document node with " + val.childNodes.length + (val.childNodes.length == 1 ? " child" : " children");
+                case Node.DOCUMENT_TYPE_NODE:
+                    return "DocumentType node";
+                case Node.DOCUMENT_FRAGMENT_NODE:
+                    return "DocumentFragment node with " + val.childNodes.length + (val.childNodes.length == 1 ? " child" : " children");
+                default:
+                    return "Node object of unknown type";
+                }
+            }
+
+        /* falls through */
+        default:
+            try {
+                return typeof val + ' "' + truncate(String(val), 1000) + '"';
+            } catch(e) {
+                return ("[stringifying object threw " + String(e) +
+                        " with type " + String(typeof e) + "]");
+            }
+        }
+    }
+    expose(format_value, "format_value");
+
+    /*
+     * Assertions
+     */
+
+    function expose_assert(f, name) {
+        function assert_wrapper(...args) {
+            let status = Test.statuses.TIMEOUT;
+            let stack = null;
+            let new_assert_index = null;
+            try {
+                if (settings.debug) {
+                    console.debug("ASSERT", name, tests.current_test && tests.current_test.name, args);
+                }
+                if (tests.output) {
+                    tests.set_assert(name, args);
+                    // Remember the newly pushed assert's index, because `apply`
+                    // below might push new asserts.
+                    new_assert_index = tests.asserts_run.length - 1;
+                }
+                const rv = f.apply(undefined, args);
+                status = Test.statuses.PASS;
+                return rv;
+            } catch(e) {
+                status = Test.statuses.FAIL;
+                stack = e.stack ? e.stack : null;
+                throw e;
+            } finally {
+                if (tests.output && !stack) {
+                    stack = get_stack();
+                }
+                if (tests.output) {
+                    tests.set_assert_status(new_assert_index, status, stack);
+                }
+            }
+        }
+        expose(assert_wrapper, name);
+    }
+
+    /**
+     * Assert that ``actual`` is strictly true
+     *
+     * @param {Any} actual - Value that is asserted to be true
+     * @param {string} [description] - Description of the condition being tested
+     */
+    function assert_true(actual, description)
+    {
+        assert(actual === true, "assert_true", description,
+                                "expected true got ${actual}", {actual:actual});
+    }
+    expose_assert(assert_true, "assert_true");
+
+    /**
+     * Assert that ``actual`` is strictly false
+     *
+     * @param {Any} actual - Value that is asserted to be false
+     * @param {string} [description] - Description of the condition being tested
+     */
+    function assert_false(actual, description)
+    {
+        assert(actual === false, "assert_false", description,
+                                 "expected false got ${actual}", {actual:actual});
+    }
+    expose_assert(assert_false, "assert_false");
+
+    function same_value(x, y) {
+        if (y !== y) {
+            //NaN case
+            return x !== x;
+        }
+        if (x === 0 && y === 0) {
+            //Distinguish +0 and -0
+            return 1/x === 1/y;
+        }
+        return x === y;
+    }
+
+    /**
+     * Assert that ``actual`` is the same value as ``expected``.
+     *
+     * For objects this compares by cobject identity; for primitives
+     * this distinguishes between 0 and -0, and has correct handling
+     * of NaN.
+     *
+     * @param {Any} actual - Test value.
+     * @param {Any} expected - Expected value.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_equals(actual, expected, description)
+    {
+         /*
+          * Test if two primitives are equal or two objects
+          * are the same object
+          */
+        if (typeof actual != typeof expected) {
+            assert(false, "assert_equals", description,
+                          "expected (" + typeof expected + ") ${expected} but got (" + typeof actual + ") ${actual}",
+                          {expected:expected, actual:actual});
+            return;
+        }
+        assert(same_value(actual, expected), "assert_equals", description,
+                                             "expected ${expected} but got ${actual}",
+                                             {expected:expected, actual:actual});
+    }
+    expose_assert(assert_equals, "assert_equals");
+
+    /**
+     * Assert that ``actual`` is not the same value as ``expected``.
+     *
+     * Comparison is as for :js:func:`assert_equals`.
+     *
+     * @param {Any} actual - Test value.
+     * @param {Any} expected - The value ``actual`` is expected to be different to.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_not_equals(actual, expected, description)
+    {
+        assert(!same_value(actual, expected), "assert_not_equals", description,
+                                              "got disallowed value ${actual}",
+                                              {actual:actual});
+    }
+    expose_assert(assert_not_equals, "assert_not_equals");
+
+    /**
+     * Assert that ``expected`` is an array and ``actual`` is one of the members.
+     * This is implemented using ``indexOf``, so doesn't handle NaN or ±0 correctly.
+     *
+     * @param {Any} actual - Test value.
+     * @param {Array} expected - An array that ``actual`` is expected to
+     * be a member of.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_in_array(actual, expected, description)
+    {
+        assert(expected.indexOf(actual) != -1, "assert_in_array", description,
+                                               "value ${actual} not in array ${expected}",
+                                               {actual:actual, expected:expected});
+    }
+    expose_assert(assert_in_array, "assert_in_array");
+
+    // This function was deprecated in July of 2015.
+    // See https://github.com/web-platform-tests/wpt/issues/2033
+    /**
+     * @deprecated
+     * Recursively compare two objects for equality.
+     *
+     * See `Issue 2033
+     * <https://github.com/web-platform-tests/wpt/issues/2033>`_ for
+     * more information.
+     *
+     * @param {Object} actual - Test value.
+     * @param {Object} expected - Expected value.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_object_equals(actual, expected, description)
+    {
+         assert(typeof actual === "object" && actual !== null, "assert_object_equals", description,
+                                                               "value is ${actual}, expected object",
+                                                               {actual: actual});
+         //This needs to be improved a great deal
+         function check_equal(actual, expected, stack)
+         {
+             stack.push(actual);
+
+             var p;
+             for (p in actual) {
+                 assert(expected.hasOwnProperty(p), "assert_object_equals", description,
+                                                    "unexpected property ${p}", {p:p});
+
+                 if (typeof actual[p] === "object" && actual[p] !== null) {
+                     if (stack.indexOf(actual[p]) === -1) {
+                         check_equal(actual[p], expected[p], stack);
+                     }
+                 } else {
+                     assert(same_value(actual[p], expected[p]), "assert_object_equals", description,
+                                                       "property ${p} expected ${expected} got ${actual}",
+                                                       {p:p, expected:expected[p], actual:actual[p]});
+                 }
+             }
+             for (p in expected) {
+                 assert(actual.hasOwnProperty(p),
+                        "assert_object_equals", description,
+                        "expected property ${p} missing", {p:p});
+             }
+             stack.pop();
+         }
+         check_equal(actual, expected, []);
+    }
+    expose_assert(assert_object_equals, "assert_object_equals");
+
+    /**
+     * Assert that ``actual`` and ``expected`` are both arrays, and that the array properties of
+     * ``actual`` and ``expected`` are all the same value (as for :js:func:`assert_equals`).
+     *
+     * @param {Array} actual - Test array.
+     * @param {Array} expected - Array that is expected to contain the same values as ``actual``.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_array_equals(actual, expected, description)
+    {
+        const max_array_length = 20;
+        function shorten_array(arr, offset = 0) {
+            // Make ", …" only show up when it would likely reduce the length, not accounting for
+            // fonts.
+            if (arr.length < max_array_length + 2) {
+                return arr;
+            }
+            // By default we want half the elements after the offset and half before
+            // But if that takes us past the end of the array, we have more before, and
+            // if it takes us before the start we have more after.
+            const length_after_offset = Math.floor(max_array_length / 2);
+            let upper_bound = Math.min(length_after_offset + offset, arr.length);
+            const lower_bound = Math.max(upper_bound - max_array_length, 0);
+
+            if (lower_bound === 0) {
+                upper_bound = max_array_length;
+            }
+
+            const output = arr.slice(lower_bound, upper_bound);
+            if (lower_bound > 0) {
+                output.beginEllipsis = true;
+            }
+            if (upper_bound < arr.length) {
+                output.endEllipsis = true;
+            }
+            return output;
+        }
+
+        assert(typeof actual === "object" && actual !== null && "length" in actual,
+               "assert_array_equals", description,
+               "value is ${actual}, expected array",
+               {actual:actual});
+        assert(actual.length === expected.length,
+               "assert_array_equals", description,
+               "lengths differ, expected array ${expected} length ${expectedLength}, got ${actual} length ${actualLength}",
+               {expected:shorten_array(expected, expected.length - 1), expectedLength:expected.length,
+                actual:shorten_array(actual, actual.length - 1), actualLength:actual.length
+               });
+
+        for (var i = 0; i < actual.length; i++) {
+            assert(actual.hasOwnProperty(i) === expected.hasOwnProperty(i),
+                   "assert_array_equals", description,
+                   "expected property ${i} to be ${expected} but was ${actual} (expected array ${arrayExpected} got ${arrayActual})",
+                   {i:i, expected:expected.hasOwnProperty(i) ? "present" : "missing",
+                    actual:actual.hasOwnProperty(i) ? "present" : "missing",
+                    arrayExpected:shorten_array(expected, i), arrayActual:shorten_array(actual, i)});
+            assert(same_value(expected[i], actual[i]),
+                   "assert_array_equals", description,
+                   "expected property ${i} to be ${expected} but got ${actual} (expected array ${arrayExpected} got ${arrayActual})",
+                   {i:i, expected:expected[i], actual:actual[i],
+                    arrayExpected:shorten_array(expected, i), arrayActual:shorten_array(actual, i)});
+        }
+    }
+    expose_assert(assert_array_equals, "assert_array_equals");
+
+    /**
+     * Assert that each array property in ``actual`` is a number within
+     * ± `epsilon` of the corresponding property in `expected`.
+     *
+     * @param {Array} actual - Array of test values.
+     * @param {Array} expected - Array of values expected to be close to the values in ``actual``.
+     * @param {number} epsilon - Magnitude of allowed difference
+     * between each value in ``actual`` and ``expected``.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_array_approx_equals(actual, expected, epsilon, description)
+    {
+        /*
+         * Test if two primitive arrays are equal within +/- epsilon
+         */
+        assert(actual.length === expected.length,
+               "assert_array_approx_equals", description,
+               "lengths differ, expected ${expected} got ${actual}",
+               {expected:expected.length, actual:actual.length});
+
+        for (var i = 0; i < actual.length; i++) {
+            assert(actual.hasOwnProperty(i) === expected.hasOwnProperty(i),
+                   "assert_array_approx_equals", description,
+                   "property ${i}, property expected to be ${expected} but was ${actual}",
+                   {i:i, expected:expected.hasOwnProperty(i) ? "present" : "missing",
+                    actual:actual.hasOwnProperty(i) ? "present" : "missing"});
+            assert(typeof actual[i] === "number",
+                   "assert_array_approx_equals", description,
+                   "property ${i}, expected a number but got a ${type_actual}",
+                   {i:i, type_actual:typeof actual[i]});
+            assert(Math.abs(actual[i] - expected[i]) <= epsilon,
+                   "assert_array_approx_equals", description,
+                   "property ${i}, expected ${expected} +/- ${epsilon}, expected ${expected} but got ${actual}",
+                   {i:i, expected:expected[i], actual:actual[i], epsilon:epsilon});
+        }
+    }
+    expose_assert(assert_array_approx_equals, "assert_array_approx_equals");
+
+    /**
+     * Assert that ``actual`` is within ± ``epsilon`` of ``expected``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} expected - Value number is expected to be close to.
+     * @param {number} epsilon - Magnitude of allowed difference between ``actual`` and ``expected``.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_approx_equals(actual, expected, epsilon, description)
+    {
+        /*
+         * Test if two primitive numbers are equal within +/- epsilon
+         */
+        assert(typeof actual === "number",
+               "assert_approx_equals", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        // The epsilon math below does not place nice with NaN and Infinity
+        // But in this case Infinity = Infinity and NaN = NaN
+        if (isFinite(actual) || isFinite(expected)) {
+            assert(Math.abs(actual - expected) <= epsilon,
+                   "assert_approx_equals", description,
+                   "expected ${expected} +/- ${epsilon} but got ${actual}",
+                   {expected:expected, actual:actual, epsilon:epsilon});
+        } else {
+            assert_equals(actual, expected);
+        }
+    }
+    expose_assert(assert_approx_equals, "assert_approx_equals");
+
+    /**
+     * Assert that ``actual`` is a number less than ``expected``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} expected - Number that ``actual`` must be less than.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_less_than(actual, expected, description)
+    {
+        /*
+         * Test if a primitive number is less than another
+         */
+        assert(typeof actual === "number",
+               "assert_less_than", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual < expected,
+               "assert_less_than", description,
+               "expected a number less than ${expected} but got ${actual}",
+               {expected:expected, actual:actual});
+    }
+    expose_assert(assert_less_than, "assert_less_than");
+
+    /**
+     * Assert that ``actual`` is a number greater than ``expected``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} expected - Number that ``actual`` must be greater than.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_greater_than(actual, expected, description)
+    {
+        /*
+         * Test if a primitive number is greater than another
+         */
+        assert(typeof actual === "number",
+               "assert_greater_than", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual > expected,
+               "assert_greater_than", description,
+               "expected a number greater than ${expected} but got ${actual}",
+               {expected:expected, actual:actual});
+    }
+    expose_assert(assert_greater_than, "assert_greater_than");
+
+    /**
+     * Assert that ``actual`` is a number greater than ``lower`` and less
+     * than ``upper`` but not equal to either.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} lower - Number that ``actual`` must be greater than.
+     * @param {number} upper - Number that ``actual`` must be less than.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_between_exclusive(actual, lower, upper, description)
+    {
+        /*
+         * Test if a primitive number is between two others
+         */
+        assert(typeof actual === "number",
+               "assert_between_exclusive", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual > lower && actual < upper,
+               "assert_between_exclusive", description,
+               "expected a number greater than ${lower} " +
+               "and less than ${upper} but got ${actual}",
+               {lower:lower, upper:upper, actual:actual});
+    }
+    expose_assert(assert_between_exclusive, "assert_between_exclusive");
+
+    /**
+     * Assert that ``actual`` is a number less than or equal to ``expected``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} expected - Number that ``actual`` must be less
+     * than or equal to.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_less_than_equal(actual, expected, description)
+    {
+        /*
+         * Test if a primitive number is less than or equal to another
+         */
+        assert(typeof actual === "number",
+               "assert_less_than_equal", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual <= expected,
+               "assert_less_than_equal", description,
+               "expected a number less than or equal to ${expected} but got ${actual}",
+               {expected:expected, actual:actual});
+    }
+    expose_assert(assert_less_than_equal, "assert_less_than_equal");
+
+    /**
+     * Assert that ``actual`` is a number greater than or equal to ``expected``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} expected - Number that ``actual`` must be greater
+     * than or equal to.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_greater_than_equal(actual, expected, description)
+    {
+        /*
+         * Test if a primitive number is greater than or equal to another
+         */
+        assert(typeof actual === "number",
+               "assert_greater_than_equal", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual >= expected,
+               "assert_greater_than_equal", description,
+               "expected a number greater than or equal to ${expected} but got ${actual}",
+               {expected:expected, actual:actual});
+    }
+    expose_assert(assert_greater_than_equal, "assert_greater_than_equal");
+
+    /**
+     * Assert that ``actual`` is a number greater than or equal to ``lower`` and less
+     * than or equal to ``upper``.
+     *
+     * @param {number} actual - Test value.
+     * @param {number} lower - Number that ``actual`` must be greater than or equal to.
+     * @param {number} upper - Number that ``actual`` must be less than or equal to.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_between_inclusive(actual, lower, upper, description)
+    {
+        /*
+         * Test if a primitive number is between to two others or equal to either of them
+         */
+        assert(typeof actual === "number",
+               "assert_between_inclusive", description,
+               "expected a number but got a ${type_actual}",
+               {type_actual:typeof actual});
+
+        assert(actual >= lower && actual <= upper,
+               "assert_between_inclusive", description,
+               "expected a number greater than or equal to ${lower} " +
+               "and less than or equal to ${upper} but got ${actual}",
+               {lower:lower, upper:upper, actual:actual});
+    }
+    expose_assert(assert_between_inclusive, "assert_between_inclusive");
+
+    /**
+     * Assert that ``actual`` matches the RegExp ``expected``.
+     *
+     * @param {String} actual - Test string.
+     * @param {RegExp} expected - RegExp ``actual`` must match.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_regexp_match(actual, expected, description) {
+        /*
+         * Test if a string (actual) matches a regexp (expected)
+         */
+        assert(expected.test(actual),
+               "assert_regexp_match", description,
+               "expected ${expected} but got ${actual}",
+               {expected:expected, actual:actual});
+    }
+    expose_assert(assert_regexp_match, "assert_regexp_match");
+
+    /**
+     * Assert that the class string of ``object`` as returned in
+     * ``Object.prototype.toString`` is equal to ``class_name``.
+     *
+     * @param {Object} object - Object to stringify.
+     * @param {string} class_string - Expected class string for ``object``.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_class_string(object, class_string, description) {
+        var actual = {}.toString.call(object);
+        var expected = "[object " + class_string + "]";
+        assert(same_value(actual, expected), "assert_class_string", description,
+                                             "expected ${expected} but got ${actual}",
+                                             {expected:expected, actual:actual});
+    }
+    expose_assert(assert_class_string, "assert_class_string");
+
+    /**
+     * Assert that ``object`` has an own property with name ``property_name``.
+     *
+     * @param {Object} object - Object that should have the given property.
+     * @param {string} property_name - Expected property name.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_own_property(object, property_name, description) {
+        assert(object.hasOwnProperty(property_name),
+               "assert_own_property", description,
+               "expected property ${p} missing", {p:property_name});
+    }
+    expose_assert(assert_own_property, "assert_own_property");
+
+    /**
+     * Assert that ``object`` does not have an own property with name ``property_name``.
+     *
+     * @param {Object} object - Object that should not have the given property.
+     * @param {string} property_name - Property name to test.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_not_own_property(object, property_name, description) {
+        assert(!object.hasOwnProperty(property_name),
+               "assert_not_own_property", description,
+               "unexpected property ${p} is found on object", {p:property_name});
+    }
+    expose_assert(assert_not_own_property, "assert_not_own_property");
+
+    function _assert_inherits(name) {
+        return function (object, property_name, description)
+        {
+            assert((typeof object === "object" && object !== null) ||
+                   typeof object === "function" ||
+                   // Or has [[IsHTMLDDA]] slot
+                   String(object) === "[object HTMLAllCollection]",
+                   name, description,
+                   "provided value is not an object");
+
+            assert("hasOwnProperty" in object,
+                   name, description,
+                   "provided value is an object but has no hasOwnProperty method");
+
+            assert(!object.hasOwnProperty(property_name),
+                   name, description,
+                   "property ${p} found on object expected in prototype chain",
+                   {p:property_name});
+
+            assert(property_name in object,
+                   name, description,
+                   "property ${p} not found in prototype chain",
+                   {p:property_name});
+        };
+    }
+
+    /**
+     * Assert that ``object`` does not have an own property with name
+     * ``property_name``, but inherits one through the prototype chain.
+     *
+     * @param {Object} object - Object that should have the given property in its prototype chain.
+     * @param {string} property_name - Expected property name.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_inherits(object, property_name, description) {
+        return _assert_inherits("assert_inherits")(object, property_name, description);
+    }
+    expose_assert(assert_inherits, "assert_inherits");
+
+    /**
+     * Alias for :js:func:`insert_inherits`.
+     *
+     * @param {Object} object - Object that should have the given property in its prototype chain.
+     * @param {string} property_name - Expected property name.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_idl_attribute(object, property_name, description) {
+        return _assert_inherits("assert_idl_attribute")(object, property_name, description);
+    }
+    expose_assert(assert_idl_attribute, "assert_idl_attribute");
+
+
+    /**
+     * Assert that ``object`` has a property named ``property_name`` and that the property is readonly.
+     *
+     * Note: The implementation tries to update the named property, so
+     * any side effects of updating will be triggered. Users are
+     * encouraged to instead inspect the property descriptor of ``property_name`` on ``object``.
+     *
+     * @param {Object} object - Object that should have the given property in its prototype chain.
+     * @param {string} property_name - Expected property name.
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_readonly(object, property_name, description)
+    {
+         var initial_value = object[property_name];
+         try {
+             //Note that this can have side effects in the case where
+             //the property has PutForwards
+             object[property_name] = initial_value + "a"; //XXX use some other value here?
+             assert(same_value(object[property_name], initial_value),
+                    "assert_readonly", description,
+                    "changing property ${p} succeeded",
+                    {p:property_name});
+         } finally {
+             object[property_name] = initial_value;
+         }
+    }
+    expose_assert(assert_readonly, "assert_readonly");
+
+    /**
+     * Assert a JS Error with the expected constructor is thrown.
+     *
+     * @param {object} constructor The expected exception constructor.
+     * @param {Function} func Function which should throw.
+     * @param {string} [description] Error description for the case that the error is not thrown.
+     */
+    function assert_throws_js(constructor, func, description)
+    {
+        assert_throws_js_impl(constructor, func, description,
+                              "assert_throws_js");
+    }
+    expose_assert(assert_throws_js, "assert_throws_js");
+
+    /**
+     * Like assert_throws_js but allows specifying the assertion type
+     * (assert_throws_js or promise_rejects_js, in practice).
+     */
+    function assert_throws_js_impl(constructor, func, description,
+                                   assertion_type)
+    {
+        try {
+            func.call(this);
+            assert(false, assertion_type, description,
+                   "${func} did not throw", {func:func});
+        } catch (e) {
+            if (e instanceof AssertionError) {
+                throw e;
+            }
+
+            // Basic sanity-checks on the thrown exception.
+            assert(typeof e === "object",
+                   assertion_type, description,
+                   "${func} threw ${e} with type ${type}, not an object",
+                   {func:func, e:e, type:typeof e});
+
+            assert(e !== null,
+                   assertion_type, description,
+                   "${func} threw null, not an object",
+                   {func:func});
+
+            // Basic sanity-check on the passed-in constructor
+            assert(typeof constructor == "function",
+                   assertion_type, description,
+                   "${constructor} is not a constructor",
+                   {constructor:constructor});
+            var obj = constructor;
+            while (obj) {
+                if (typeof obj === "function" &&
+                    obj.name === "Error") {
+                    break;
+                }
+                obj = Object.getPrototypeOf(obj);
+            }
+            assert(obj != null,
+                   assertion_type, description,
+                   "${constructor} is not an Error subtype",
+                   {constructor:constructor});
+
+            // And checking that our exception is reasonable
+            assert(e.constructor === constructor &&
+                   e.name === constructor.name,
+                   assertion_type, description,
+                   "${func} threw ${actual} (${actual_name}) expected instance of ${expected} (${expected_name})",
+                   {func:func, actual:e, actual_name:e.name,
+                    expected:constructor,
+                    expected_name:constructor.name});
+        }
+    }
+
+    // TODO: Figure out how to document the overloads better.
+    // sphinx-js doesn't seem to handle @variation correctly,
+    // and only expects a single JSDoc entry per function.
+    /**
+     * Assert a DOMException with the expected type is thrown.
+     *
+     * There are two ways of calling assert_throws_dom:
+     *
+     * 1) If the DOMException is expected to come from the current global, the
+     * second argument should be the function expected to throw and a third,
+     * optional, argument is the assertion description.
+     *
+     * 2) If the DOMException is expected to come from some other global, the
+     * second argument should be the DOMException constructor from that global,
+     * the third argument the function expected to throw, and the fourth, optional,
+     * argument the assertion description.
+     *
+     * @param {number|string} type - The expected exception name or
+     * code.  See the `table of names and codes
+     * <https://webidl.spec.whatwg.org/#dfn-error-names-table>`_. If a
+     * number is passed it should be one of the numeric code values in
+     * that table (e.g. 3, 4, etc).  If a string is passed it can
+     * either be an exception name (e.g. "HierarchyRequestError",
+     * "WrongDocumentError") or the name of the corresponding error
+     * code (e.g. "``HIERARCHY_REQUEST_ERR``", "``WRONG_DOCUMENT_ERR``").
+     * @param {Function} descriptionOrFunc - The function expected to
+     * throw (if the exception comes from another global), or the
+     * optional description of the condition being tested (if the
+     * exception comes from the current global).
+     * @param {string} [description] - Description of the condition
+     * being tested (if the exception comes from another global).
+     *
+     */
+    function assert_throws_dom(type, funcOrConstructor, descriptionOrFunc, maybeDescription)
+    {
+        let constructor, func, description;
+        if (funcOrConstructor.name === "DOMException") {
+            constructor = funcOrConstructor;
+            func = descriptionOrFunc;
+            description = maybeDescription;
+        } else {
+            constructor = self.DOMException;
+            func = funcOrConstructor;
+            description = descriptionOrFunc;
+            assert(maybeDescription === undefined,
+                   "Too many args pased to no-constructor version of assert_throws_dom");
+        }
+        assert_throws_dom_impl(type, func, description, "assert_throws_dom", constructor)
+    }
+    expose_assert(assert_throws_dom, "assert_throws_dom");
+
+    /**
+     * Similar to assert_throws_dom but allows specifying the assertion type
+     * (assert_throws_dom or promise_rejects_dom, in practice).  The
+     * "constructor" argument must be the DOMException constructor from the
+     * global we expect the exception to come from.
+     */
+    function assert_throws_dom_impl(type, func, description, assertion_type, constructor)
+    {
+        try {
+            func.call(this);
+            assert(false, assertion_type, description,
+                   "${func} did not throw", {func:func});
+        } catch (e) {
+            if (e instanceof AssertionError) {
+                throw e;
+            }
+
+            // Basic sanity-checks on the thrown exception.
+            assert(typeof e === "object",
+                   assertion_type, description,
+                   "${func} threw ${e} with type ${type}, not an object",
+                   {func:func, e:e, type:typeof e});
+
+            assert(e !== null,
+                   assertion_type, description,
+                   "${func} threw null, not an object",
+                   {func:func});
+
+            // Sanity-check our type
+            assert(typeof type == "number" ||
+                   typeof type == "string",
+                   assertion_type, description,
+                   "${type} is not a number or string",
+                   {type:type});
+
+            var codename_name_map = {
+                INDEX_SIZE_ERR: 'IndexSizeError',
+                HIERARCHY_REQUEST_ERR: 'HierarchyRequestError',
+                WRONG_DOCUMENT_ERR: 'WrongDocumentError',
+                INVALID_CHARACTER_ERR: 'InvalidCharacterError',
+                NO_MODIFICATION_ALLOWED_ERR: 'NoModificationAllowedError',
+                NOT_FOUND_ERR: 'NotFoundError',
+                NOT_SUPPORTED_ERR: 'NotSupportedError',
+                INUSE_ATTRIBUTE_ERR: 'InUseAttributeError',
+                INVALID_STATE_ERR: 'InvalidStateError',
+                SYNTAX_ERR: 'SyntaxError',
+                INVALID_MODIFICATION_ERR: 'InvalidModificationError',
+                NAMESPACE_ERR: 'NamespaceError',
+                INVALID_ACCESS_ERR: 'InvalidAccessError',
+                TYPE_MISMATCH_ERR: 'TypeMismatchError',
+                SECURITY_ERR: 'SecurityError',
+                NETWORK_ERR: 'NetworkError',
+                ABORT_ERR: 'AbortError',
+                URL_MISMATCH_ERR: 'URLMismatchError',
+                QUOTA_EXCEEDED_ERR: 'QuotaExceededError',
+                TIMEOUT_ERR: 'TimeoutError',
+                INVALID_NODE_TYPE_ERR: 'InvalidNodeTypeError',
+                DATA_CLONE_ERR: 'DataCloneError'
+            };
+
+            var name_code_map = {
+                IndexSizeError: 1,
+                HierarchyRequestError: 3,
+                WrongDocumentError: 4,
+                InvalidCharacterError: 5,
+                NoModificationAllowedError: 7,
+                NotFoundError: 8,
+                NotSupportedError: 9,
+                InUseAttributeError: 10,
+                InvalidStateError: 11,
+                SyntaxError: 12,
+                InvalidModificationError: 13,
+                NamespaceError: 14,
+                InvalidAccessError: 15,
+                TypeMismatchError: 17,
+                SecurityError: 18,
+                NetworkError: 19,
+                AbortError: 20,
+                URLMismatchError: 21,
+                QuotaExceededError: 22,
+                TimeoutError: 23,
+                InvalidNodeTypeError: 24,
+                DataCloneError: 25,
+
+                EncodingError: 0,
+                NotReadableError: 0,
+                UnknownError: 0,
+                ConstraintError: 0,
+                DataError: 0,
+                TransactionInactiveError: 0,
+                ReadOnlyError: 0,
+                VersionError: 0,
+                OperationError: 0,
+                NotAllowedError: 0,
+                OptOutError: 0
+            };
+
+            var code_name_map = {};
+            for (var key in name_code_map) {
+                if (name_code_map[key] > 0) {
+                    code_name_map[name_code_map[key]] = key;
+                }
+            }
+
+            var required_props = {};
+            var name;
+
+            if (typeof type === "number") {
+                if (type === 0) {
+                    throw new AssertionError('Test bug: ambiguous DOMException code 0 passed to assert_throws_dom()');
+                } else if (!(type in code_name_map)) {
+                    throw new AssertionError('Test bug: unrecognized DOMException code "' + type + '" passed to assert_throws_dom()');
+                }
+                name = code_name_map[type];
+                required_props.code = type;
+            } else if (typeof type === "string") {
+                name = type in codename_name_map ? codename_name_map[type] : type;
+                if (!(name in name_code_map)) {
+                    throw new AssertionError('Test bug: unrecognized DOMException code name or name "' + type + '" passed to assert_throws_dom()');
+                }
+
+                required_props.code = name_code_map[name];
+            }
+
+            if (required_props.code === 0 ||
+               ("name" in e &&
+                e.name !== e.name.toUpperCase() &&
+                e.name !== "DOMException")) {
+                // New style exception: also test the name property.
+                required_props.name = name;
+            }
+
+            for (var prop in required_props) {
+                assert(prop in e && e[prop] == required_props[prop],
+                       assertion_type, description,
+                       "${func} threw ${e} that is not a DOMException " + type + ": property ${prop} is equal to ${actual}, expected ${expected}",
+                       {func:func, e:e, prop:prop, actual:e[prop], expected:required_props[prop]});
+            }
+
+            // Check that the exception is from the right global.  This check is last
+            // so more specific, and more informative, checks on the properties can
+            // happen in case a totally incorrect exception is thrown.
+            assert(e.constructor === constructor,
+                   assertion_type, description,
+                   "${func} threw an exception from the wrong global",
+                   {func});
+
+        }
+    }
+
+    /**
+     * Assert the provided value is thrown.
+     *
+     * @param {value} exception The expected exception.
+     * @param {Function} func Function which should throw.
+     * @param {string} [description] Error description for the case that the error is not thrown.
+     */
+    function assert_throws_exactly(exception, func, description)
+    {
+        assert_throws_exactly_impl(exception, func, description,
+                                   "assert_throws_exactly");
+    }
+    expose_assert(assert_throws_exactly, "assert_throws_exactly");
+
+    /**
+     * Like assert_throws_exactly but allows specifying the assertion type
+     * (assert_throws_exactly or promise_rejects_exactly, in practice).
+     */
+    function assert_throws_exactly_impl(exception, func, description,
+                                        assertion_type)
+    {
+        try {
+            func.call(this);
+            assert(false, assertion_type, description,
+                   "${func} did not throw", {func:func});
+        } catch (e) {
+            if (e instanceof AssertionError) {
+                throw e;
+            }
+
+            assert(same_value(e, exception), assertion_type, description,
+                   "${func} threw ${e} but we expected it to throw ${exception}",
+                   {func:func, e:e, exception:exception});
+        }
+    }
+
+    /**
+     * Asserts if called. Used to ensure that a specific codepath is
+     * not taken e.g. that an error event isn't fired.
+     *
+     * @param {string} [description] - Description of the condition being tested.
+     */
+    function assert_unreached(description) {
+         assert(false, "assert_unreached", description,
+                "Reached unreachable code");
+    }
+    expose_assert(assert_unreached, "assert_unreached");
+
+    /**
+     * @callback AssertFunc
+     * @param {Any} actual
+     * @param {Any} expected
+     * @param {Any[]} args
+     */
+
+    /**
+     * Asserts that ``actual`` matches at least one value of ``expected``
+     * according to a comparison defined by ``assert_func``.
+     *
+     * Note that tests with multiple allowed pass conditions are bad
+     * practice unless the spec specifically allows multiple
+     * behaviours. Test authors should not use this method simply to
+     * hide UA bugs.
+     *
+     * @param {AssertFunc} assert_func - Function to compare actual
+     * and expected. It must throw when the comparison fails and
+     * return when the comparison passes.
+     * @param {Any} actual - Test value.
+     * @param {Array} expected_array - Array of possible expected values.
+     * @param {Any[]} args - Additional arguments to pass to ``assert_func``.
+     */
+    function assert_any(assert_func, actual, expected_array, ...args)
+    {
+        var errors = [];
+        var passed = false;
+        forEach(expected_array,
+                function(expected)
+                {
+                    try {
+                        assert_func.apply(this, [actual, expected].concat(args));
+                        passed = true;
+                    } catch (e) {
+                        errors.push(e.message);
+                    }
+                });
+        if (!passed) {
+            throw new AssertionError(errors.join("\n\n"));
+        }
+    }
+    // FIXME: assert_any cannot use expose_assert, because assert_wrapper does
+    // not support nested assert calls (e.g. to assert_func). We need to
+    // support bypassing assert_wrapper for the inner asserts here.
+    expose(assert_any, "assert_any");
+
+    /**
+     * Assert that a feature is implemented, based on a 'truthy' condition.
+     *
+     * This function should be used to early-exit from tests in which there is
+     * no point continuing without support for a non-optional spec or spec
+     * feature. For example:
+     *
+     *     assert_implements(window.Foo, 'Foo is not supported');
+     *
+     * @param {object} condition The truthy value to test
+     * @param {string} [description] Error description for the case that the condition is not truthy.
+     */
+    function assert_implements(condition, description) {
+        assert(!!condition, "assert_implements", description);
+    }
+    expose_assert(assert_implements, "assert_implements")
+
+    /**
+     * Assert that an optional feature is implemented, based on a 'truthy' condition.
+     *
+     * This function should be used to early-exit from tests in which there is
+     * no point continuing without support for an explicitly optional spec or
+     * spec feature. For example:
+     *
+     *     assert_implements_optional(video.canPlayType("video/webm"),
+     *                                "webm video playback not supported");
+     *
+     * @param {object} condition The truthy value to test
+     * @param {string} [description] Error description for the case that the condition is not truthy.
+     */
+    function assert_implements_optional(condition, description) {
+        if (!condition) {
+            throw new OptionalFeatureUnsupportedError(description);
+        }
+    }
+    expose_assert(assert_implements_optional, "assert_implements_optional");
+
+    /**
+     * @class
+     *
+     * A single subtest. A Test is not constructed directly but via the
+     * :js:func:`test`, :js:func:`async_test` or :js:func:`promise_test` functions.
+     *
+     * @param {string} name - This must be unique in a given file and must be
+     * invariant between runs.
+     *
+     */
+    function Test(name, properties)
+    {
+        if (tests.file_is_test && tests.tests.length) {
+            throw new Error("Tried to create a test with file_is_test");
+        }
+        /** The test name. */
+        this.name = name;
+
+        this.phase = (tests.is_aborted || tests.phase === tests.phases.COMPLETE) ?
+            this.phases.COMPLETE : this.phases.INITIAL;
+
+        /** The test status code.*/
+        this.status = this.NOTRUN;
+        this.timeout_id = null;
+        this.index = null;
+
+        this.properties = properties || {};
+        this.timeout_length = settings.test_timeout;
+        if (this.timeout_length !== null) {
+            this.timeout_length *= tests.timeout_multiplier;
+        }
+
+        /** A message indicating the reason for test failure. */
+        this.message = null;
+        /** Stack trace in case of failure. */
+        this.stack = null;
+
+        this.steps = [];
+        this._is_promise_test = false;
+
+        this.cleanup_callbacks = [];
+        this._user_defined_cleanup_count = 0;
+        this._done_callbacks = [];
+
+        if (typeof AbortController === "function") {
+            this._abortController = new AbortController();
+        }
+
+        // Tests declared following harness completion are likely an indication
+        // of a programming error, but they cannot be reported
+        // deterministically.
+        if (tests.phase === tests.phases.COMPLETE) {
+            return;
+        }
+
+        tests.push(this);
+    }
+
+    /**
+     * Enum of possible test statuses.
+     *
+     * :values:
+     *   - ``PASS``
+     *   - ``FAIL``
+     *   - ``TIMEOUT``
+     *   - ``NOTRUN``
+     *   - ``PRECONDITION_FAILED``
+     */
+    Test.statuses = {
+        PASS:0,
+        FAIL:1,
+        TIMEOUT:2,
+        NOTRUN:3,
+        PRECONDITION_FAILED:4
+    };
+
+    Test.prototype = merge({}, Test.statuses);
+
+    Test.prototype.phases = {
+        INITIAL:0,
+        STARTED:1,
+        HAS_RESULT:2,
+        CLEANING:3,
+        COMPLETE:4
+    };
+
+    Test.prototype.status_formats = {
+        0: "Pass",
+        1: "Fail",
+        2: "Timeout",
+        3: "Not Run",
+        4: "Optional Feature Unsupported",
+    }
+
+    Test.prototype.format_status = function() {
+        return this.status_formats[this.status];
+    }
+
+    Test.prototype.structured_clone = function()
+    {
+        if (!this._structured_clone) {
+            var msg = this.message;
+            msg = msg ? String(msg) : msg;
+            this._structured_clone = merge({
+                name:String(this.name),
+                properties:merge({}, this.properties),
+                phases:merge({}, this.phases)
+            }, Test.statuses);
+        }
+        this._structured_clone.status = this.status;
+        this._structured_clone.message = this.message;
+        this._structured_clone.stack = this.stack;
+        this._structured_clone.index = this.index;
+        this._structured_clone.phase = this.phase;
+        return this._structured_clone;
+    };
+
+    /**
+     * Run a single step of an ongoing test.
+     *
+     * @param {string} func - Callback function to run as a step. If
+     * this throws an :js:func:`AssertionError`, or any other
+     * exception, the :js:class:`Test` status is set to ``FAIL``.
+     * @param {Object} [this_obj] - The object to use as the this
+     * value when calling ``func``. Defaults to the  :js:class:`Test` object.
+     */
+    Test.prototype.step = function(func, this_obj)
+    {
+        if (this.phase > this.phases.STARTED) {
+            return;
+        }
+
+        if (settings.debug && this.phase !== this.phases.STARTED) {
+            console.log("TEST START", this.name);
+        }
+        this.phase = this.phases.STARTED;
+        //If we don't get a result before the harness times out that will be a test timeout
+        this.set_status(this.TIMEOUT, "Test timed out");
+
+        tests.started = true;
+        tests.current_test = this;
+        tests.notify_test_state(this);
+
+        if (this.timeout_id === null) {
+            this.set_timeout();
+        }
+
+        this.steps.push(func);
+
+        if (arguments.length === 1) {
+            this_obj = this;
+        }
+
+        if (settings.debug) {
+            console.debug("TEST STEP", this.name);
+        }
+
+        try {
+            return func.apply(this_obj, Array.prototype.slice.call(arguments, 2));
+        } catch (e) {
+            if (this.phase >= this.phases.HAS_RESULT) {
+                return;
+            }
+            var status = e instanceof OptionalFeatureUnsupportedError ? this.PRECONDITION_FAILED : this.FAIL;
+            var message = String((typeof e === "object" && e !== null) ? e.message : e);
+            var stack = e.stack ? e.stack : null;
+
+            this.set_status(status, message, stack);
+            this.phase = this.phases.HAS_RESULT;
+            this.done();
+        } finally {
+            this.current_test = null;
+        }
+    };
+
+    /**
+     * Wrap a function so that it runs as a step of the current test.
+     *
+     * This allows creating a callback function that will run as a
+     * test step.
+     *
+     * @example
+     * let t = async_test("Example");
+     * onload = t.step_func(e => {
+     *   assert_equals(e.name, "load");
+     *   // Mark the test as complete.
+     *   t.done();
+     * })
+     *
+     * @param {string} func - Function to run as a step. If this
+     * throws an :js:func:`AssertionError`, or any other exception,
+     * the :js:class:`Test` status is set to ``FAIL``.
+     * @param {Object} [this_obj] - The object to use as the this
+     * value when calling ``func``. Defaults to the :js:class:`Test` object.
+     */
+    Test.prototype.step_func = function(func, this_obj)
+    {
+        var test_this = this;
+
+        if (arguments.length === 1) {
+            this_obj = test_this;
+        }
+
+        return function()
+        {
+            return test_this.step.apply(test_this, [func, this_obj].concat(
+                Array.prototype.slice.call(arguments)));
+        };
+    };
+
+    /**
+     * Wrap a function so that it runs as a step of the current test,
+     * and automatically marks the test as complete if the function
+     * returns without error.
+     *
+     * @param {string} func - Function to run as a step. If this
+     * throws an :js:func:`AssertionError`, or any other exception,
+     * the :js:class:`Test` status is set to ``FAIL``. If it returns
+     * without error the status is set to ``PASS``.
+     * @param {Object} [this_obj] - The object to use as the this
+     * value when calling `func`. Defaults to the :js:class:`Test` object.
+     */
+    Test.prototype.step_func_done = function(func, this_obj)
+    {
+        var test_this = this;
+
+        if (arguments.length === 1) {
+            this_obj = test_this;
+        }
+
+        return function()
+        {
+            if (func) {
+                test_this.step.apply(test_this, [func, this_obj].concat(
+                    Array.prototype.slice.call(arguments)));
+            }
+            test_this.done();
+        };
+    };
+
+    /**
+     * Return a function that automatically sets the current test to
+     * ``FAIL`` if it's called.
+     *
+     * @param {string} [description] - Error message to add to assert
+     * in case of failure.
+     *
+     */
+    Test.prototype.unreached_func = function(description)
+    {
+        return this.step_func(function() {
+            assert_unreached(description);
+        });
+    };
+
+    /**
+     * Run a function as a step of the test after a given timeout.
+     *
+     * This multiplies the timeout by the global timeout multiplier to
+     * account for the expected execution speed of the current test
+     * environment. For example ``test.step_timeout(f, 2000)`` with a
+     * timeout multiplier of 2 will wait for 4000ms before calling ``f``.
+     *
+     * In general it's encouraged to use :js:func:`Test.step_wait` or
+     * :js:func:`step_wait_func` in preference to this function where possible,
+     * as they provide better test performance.
+     *
+     * @param {Function} func - Function to run as a test
+     * step.
+     * @param {number} timeout - Time in ms to wait before running the
+     * test step. The actual wait time is ``timeout`` x
+     * ``timeout_multiplier``.
+     *
+     */
+    Test.prototype.step_timeout = function(func, timeout) {
+        var test_this = this;
+        var args = Array.prototype.slice.call(arguments, 2);
+        return setTimeout(this.step_func(function() {
+            return func.apply(test_this, args);
+        }), timeout * tests.timeout_multiplier);
+    };
+
+    /**
+     * Poll for a function to return true, and call a callback
+     * function once it does, or assert if a timeout is
+     * reached. This is preferred over a simple step_timeout
+     * whenever possible since it allows the timeout to be longer
+     * to reduce intermittents without compromising test execution
+     * speed when the condition is quickly met.
+     *
+     * @param {Function} cond A function taking no arguments and
+     *                        returning a boolean. The callback is called
+     *                        when this function returns true.
+     * @param {Function} func A function taking no arguments to call once
+     *                        the condition is met.
+     * @param {string} [description] Error message to add to assert in case of
+     *                               failure.
+     * @param {number} timeout Timeout in ms. This is multiplied by the global
+     *                         timeout_multiplier
+     * @param {number} interval Polling interval in ms
+     *
+     */
+    Test.prototype.step_wait_func = function(cond, func, description,
+                                             timeout=3000, interval=100) {
+        var timeout_full = timeout * tests.timeout_multiplier;
+        var remaining = Math.ceil(timeout_full / interval);
+        var test_this = this;
+
+        var wait_for_inner = test_this.step_func(() => {
+            if (cond()) {
+                func();
+            } else {
+                if(remaining === 0) {
+                    assert(false, "step_wait_func", description,
+                           "Timed out waiting on condition");
+                }
+                remaining--;
+                setTimeout(wait_for_inner, interval);
+            }
+        });
+
+        wait_for_inner();
+    };
+
+    /**
+     * Poll for a function to return true, and invoke a callback
+     * followed by this.done() once it does, or assert if a timeout
+     * is reached. This is preferred over a simple step_timeout
+     * whenever possible since it allows the timeout to be longer
+     * to reduce intermittents without compromising test execution speed
+     * when the condition is quickly met.
+     *
+     * @example
+     * async_test(t => {
+     *  const popup = window.open("resources/coop-coep.py?coop=same-origin&coep=&navigate=about:blank");
+     *  t.add_cleanup(() => popup.close());
+     *  assert_equals(window, popup.opener);
+     *
+     *  popup.onload = t.step_func(() => {
+     *    assert_true(popup.location.href.endsWith("&navigate=about:blank"));
+     *    // Use step_wait_func_done as about:blank cannot message back.
+     *    t.step_wait_func_done(() => popup.location.href === "about:blank");
+     *  });
+     * }, "Navigating a popup to about:blank");
+     *
+     * @param {Function} cond A function taking no arguments and
+     *                        returning a boolean. The callback is called
+     *                        when this function returns true.
+     * @param {Function} func A function taking no arguments to call once
+     *                        the condition is met.
+     * @param {string} [description] Error message to add to assert in case of
+     *                               failure.
+     * @param {number} timeout Timeout in ms. This is multiplied by the global
+     *                         timeout_multiplier
+     * @param {number} interval Polling interval in ms
+     *
+     */
+    Test.prototype.step_wait_func_done = function(cond, func, description,
+                                                  timeout=3000, interval=100) {
+         this.step_wait_func(cond, () => {
+            if (func) {
+                func();
+            }
+            this.done();
+         }, description, timeout, interval);
+    };
+
+    /**
+     * Poll for a function to return true, and resolve a promise
+     * once it does, or assert if a timeout is reached. This is
+     * preferred over a simple step_timeout whenever possible
+     * since it allows the timeout to be longer to reduce
+     * intermittents without compromising test execution speed
+     * when the condition is quickly met.
+     *
+     * @example
+     * promise_test(async t => {
+     *  // …
+     * await t.step_wait(() => frame.contentDocument === null, "Frame navigated to a cross-origin document");
+     * // …
+     * }, "");
+     *
+     * @param {Function} cond A function taking no arguments and
+     *                        returning a boolean.
+     * @param {string} [description] Error message to add to assert in case of
+     *                              failure.
+     * @param {number} timeout Timeout in ms. This is multiplied by the global
+     *                         timeout_multiplier
+     * @param {number} interval Polling interval in ms
+     * @returns {Promise} Promise resolved once cond is met.
+     *
+     */
+    Test.prototype.step_wait = function(cond, description, timeout=3000, interval=100) {
+        return new Promise(resolve => {
+            this.step_wait_func(cond, resolve, description, timeout, interval);
+        });
+    }
+
+    /*
+     * Private method for registering cleanup functions. `testharness.js`
+     * internals should use this method instead of the public `add_cleanup`
+     * method in order to hide implementation details from the harness status
+     * message in the case errors.
+     */
+    Test.prototype._add_cleanup = function(callback) {
+        this.cleanup_callbacks.push(callback);
+    };
+
+    /**
+     * Schedule a function to be run after the test result is known, regardless
+     * of passing or failing state.
+     *
+     * The behavior of this function will not
+     * influence the result of the test, but if an exception is thrown, the
+     * test harness will report an error.
+     *
+     * @param {Function} callback - The cleanup function to run. This
+     * is called with no arguments.
+     */
+    Test.prototype.add_cleanup = function(callback) {
+        this._user_defined_cleanup_count += 1;
+        this._add_cleanup(callback);
+    };
+
+    Test.prototype.set_timeout = function()
+    {
+        if (this.timeout_length !== null) {
+            var this_obj = this;
+            this.timeout_id = setTimeout(function()
+                                         {
+                                             this_obj.timeout();
+                                         }, this.timeout_length);
+        }
+    };
+
+    Test.prototype.set_status = function(status, message, stack)
+    {
+        this.status = status;
+        this.message = message;
+        this.stack = stack ? stack : null;
+    };
+
+    /**
+     * Manually set the test status to ``TIMEOUT``.
+     */
+    Test.prototype.timeout = function()
+    {
+        this.timeout_id = null;
+        this.set_status(this.TIMEOUT, "Test timed out");
+        this.phase = this.phases.HAS_RESULT;
+        this.done();
+    };
+
+    /**
+     * Manually set the test status to ``TIMEOUT``.
+     *
+     * Alias for `Test.timeout <#Test.timeout>`_.
+     */
+    Test.prototype.force_timeout = function() {
+        return this.timeout();
+    };
+
+    /**
+     * Mark the test as complete.
+     *
+     * This sets the test status to ``PASS`` if no other status was
+     * already recorded. Any subsequent attempts to run additional
+     * test steps will be ignored.
+     *
+     * After setting the test status any test cleanup functions will
+     * be run.
+     */
+    Test.prototype.done = function()
+    {
+        if (this.phase >= this.phases.CLEANING) {
+            return;
+        }
+
+        if (this.phase <= this.phases.STARTED) {
+            this.set_status(this.PASS, null);
+        }
+
+        if (global_scope.clearTimeout) {
+            clearTimeout(this.timeout_id);
+        }
+
+        if (settings.debug) {
+            console.log("TEST DONE",
+                        this.status,
+                        this.name);
+        }
+
+        this.cleanup();
+    };
+
+    function add_test_done_callback(test, callback)
+    {
+        if (test.phase === test.phases.COMPLETE) {
+            callback();
+            return;
+        }
+
+        test._done_callbacks.push(callback);
+    }
+
+    /*
+     * Invoke all specified cleanup functions. If one or more produce an error,
+     * the context is in an unpredictable state, so all further testing should
+     * be cancelled.
+     */
+    Test.prototype.cleanup = function() {
+        var errors = [];
+        var bad_value_count = 0;
+        function on_error(e) {
+            errors.push(e);
+            // Abort tests immediately so that tests declared within subsequent
+            // cleanup functions are not run.
+            tests.abort();
+        }
+        var this_obj = this;
+        var results = [];
+
+        this.phase = this.phases.CLEANING;
+
+        if (this._abortController) {
+            this._abortController.abort("Test cleanup");
+        }
+
+        forEach(this.cleanup_callbacks,
+                function(cleanup_callback) {
+                    var result;
+
+                    try {
+                        result = cleanup_callback();
+                    } catch (e) {
+                        on_error(e);
+                        return;
+                    }
+
+                    if (!is_valid_cleanup_result(this_obj, result)) {
+                        bad_value_count += 1;
+                        // Abort tests immediately so that tests declared
+                        // within subsequent cleanup functions are not run.
+                        tests.abort();
+                    }
+
+                    results.push(result);
+                });
+
+        if (!this._is_promise_test) {
+            cleanup_done(this_obj, errors, bad_value_count);
+        } else {
+            all_async(results,
+                      function(result, done) {
+                          if (result && typeof result.then === "function") {
+                              result
+                                  .then(null, on_error)
+                                  .then(done);
+                          } else {
+                              done();
+                          }
+                      },
+                      function() {
+                          cleanup_done(this_obj, errors, bad_value_count);
+                      });
+        }
+    };
+
+    /*
+     * Determine if the return value of a cleanup function is valid for a given
+     * test. Any test may return the value `undefined`. Tests created with
+     * `promise_test` may alternatively return "thenable" object values.
+     */
+    function is_valid_cleanup_result(test, result) {
+        if (result === undefined) {
+            return true;
+        }
+
+        if (test._is_promise_test) {
+            return result && typeof result.then === "function";
+        }
+
+        return false;
+    }
+
+    function cleanup_done(test, errors, bad_value_count) {
+        if (errors.length || bad_value_count) {
+            var total = test._user_defined_cleanup_count;
+
+            tests.status.status = tests.status.ERROR;
+            tests.status.stack = null;
+            tests.status.message = "Test named '" + test.name +
+                "' specified " + total +
+                " 'cleanup' function" + (total > 1 ? "s" : "");
+
+            if (errors.length) {
+                tests.status.message += ", and " + errors.length + " failed";
+                tests.status.stack = ((typeof errors[0] === "object" &&
+                                       errors[0].hasOwnProperty("stack")) ?
+                                      errors[0].stack : null);
+            }
+
+            if (bad_value_count) {
+                var type = test._is_promise_test ?
+                   "non-thenable" : "non-undefined";
+                tests.status.message += ", and " + bad_value_count +
+                    " returned a " + type + " value";
+            }
+
+            tests.status.message += ".";
+        }
+
+        test.phase = test.phases.COMPLETE;
+        tests.result(test);
+        forEach(test._done_callbacks,
+                function(callback) {
+                    callback();
+                });
+        test._done_callbacks.length = 0;
+    }
+
+    /**
+     * Gives an AbortSignal that will be aborted when the test finishes.
+     */
+    Test.prototype.get_signal = function() {
+        if (!this._abortController) {
+            throw new Error("AbortController is not supported in this browser");
+        }
+        return this._abortController.signal;
+    }
+
+    /**
+     * A RemoteTest object mirrors a Test object on a remote worker. The
+     * associated RemoteWorker updates the RemoteTest object in response to
+     * received events. In turn, the RemoteTest object replicates these events
+     * on the local document. This allows listeners (test result reporting
+     * etc..) to transparently handle local and remote events.
+     */
+    function RemoteTest(clone) {
+        var this_obj = this;
+        Object.keys(clone).forEach(
+                function(key) {
+                    this_obj[key] = clone[key];
+                });
+        this.index = null;
+        this.phase = this.phases.INITIAL;
+        this.update_state_from(clone);
+        this._done_callbacks = [];
+        tests.push(this);
+    }
+
+    RemoteTest.prototype.structured_clone = function() {
+        var clone = {};
+        Object.keys(this).forEach(
+                (function(key) {
+                    var value = this[key];
+                    // `RemoteTest` instances are responsible for managing
+                    // their own "done" callback functions, so those functions
+                    // are not relevant in other execution contexts. Because of
+                    // this (and because Function values cannot be serialized
+                    // for cross-realm transmittance), the property should not
+                    // be considered when cloning instances.
+                    if (key === '_done_callbacks' ) {
+                        return;
+                    }
+
+                    if (typeof value === "object" && value !== null) {
+                        clone[key] = merge({}, value);
+                    } else {
+                        clone[key] = value;
+                    }
+                }).bind(this));
+        clone.phases = merge({}, this.phases);
+        return clone;
+    };
+
+    /**
+     * `RemoteTest` instances are objects which represent tests running in
+     * another realm. They do not define "cleanup" functions (if necessary,
+     * such functions are defined on the associated `Test` instance within the
+     * external realm). However, `RemoteTests` may have "done" callbacks (e.g.
+     * as attached by the `Tests` instance responsible for tracking the overall
+     * test status in the parent realm). The `cleanup` method delegates to
+     * `done` in order to ensure that such callbacks are invoked following the
+     * completion of the `RemoteTest`.
+     */
+    RemoteTest.prototype.cleanup = function() {
+        this.done();
+    };
+    RemoteTest.prototype.phases = Test.prototype.phases;
+    RemoteTest.prototype.update_state_from = function(clone) {
+        this.status = clone.status;
+        this.message = clone.message;
+        this.stack = clone.stack;
+        if (this.phase === this.phases.INITIAL) {
+            this.phase = this.phases.STARTED;
+        }
+    };
+    RemoteTest.prototype.done = function() {
+        this.phase = this.phases.COMPLETE;
+
+        forEach(this._done_callbacks,
+                function(callback) {
+                    callback();
+                });
+    }
+
+    RemoteTest.prototype.format_status = function() {
+        return Test.prototype.status_formats[this.status];
+    }
+
+    /*
+     * A RemoteContext listens for test events from a remote test context, such
+     * as another window or a worker. These events are then used to construct
+     * and maintain RemoteTest objects that mirror the tests running in the
+     * remote context.
+     *
+     * An optional third parameter can be used as a predicate to filter incoming
+     * MessageEvents.
+     */
+    function RemoteContext(remote, message_target, message_filter) {
+        this.running = true;
+        this.started = false;
+        this.tests = new Array();
+        this.early_exception = null;
+
+        var this_obj = this;
+        // If remote context is cross origin assigning to onerror is not
+        // possible, so silently catch those errors.
+        try {
+          remote.onerror = function(error) { this_obj.remote_error(error); };
+        } catch (e) {
+          // Ignore.
+        }
+
+        // Keeping a reference to the remote object and the message handler until
+        // remote_done() is seen prevents the remote object and its message channel
+        // from going away before all the messages are dispatched.
+        this.remote = remote;
+        this.message_target = message_target;
+        this.message_handler = function(message) {
+            var passesFilter = !message_filter || message_filter(message);
+            // The reference to the `running` property in the following
+            // condition is unnecessary because that value is only set to
+            // `false` after the `message_handler` function has been
+            // unsubscribed.
+            // TODO: Simplify the condition by removing the reference.
+            if (this_obj.running && message.data && passesFilter &&
+                (message.data.type in this_obj.message_handlers)) {
+                this_obj.message_handlers[message.data.type].call(this_obj, message.data);
+            }
+        };
+
+        if (self.Promise) {
+            this.done = new Promise(function(resolve) {
+                this_obj.doneResolve = resolve;
+            });
+        }
+
+        this.message_target.addEventListener("message", this.message_handler);
+    }
+
+    RemoteContext.prototype.remote_error = function(error) {
+        if (error.preventDefault) {
+            error.preventDefault();
+        }
+
+        // Defer interpretation of errors until the testing protocol has
+        // started and the remote test's `allow_uncaught_exception` property
+        // is available.
+        if (!this.started) {
+            this.early_exception = error;
+        } else if (!this.allow_uncaught_exception) {
+            this.report_uncaught(error);
+        }
+    };
+
+    RemoteContext.prototype.report_uncaught = function(error) {
+        var message = error.message || String(error);
+        var filename = (error.filename ? " " + error.filename: "");
+        // FIXME: Display remote error states separately from main document
+        // error state.
+        tests.set_status(tests.status.ERROR,
+                         "Error in remote" + filename + ": " + message,
+                         error.stack);
+    };
+
+    RemoteContext.prototype.start = function(data) {
+        this.started = true;
+        this.allow_uncaught_exception = data.properties.allow_uncaught_exception;
+
+        if (this.early_exception && !this.allow_uncaught_exception) {
+            this.report_uncaught(this.early_exception);
+        }
+    };
+
+    RemoteContext.prototype.test_state = function(data) {
+        var remote_test = this.tests[data.test.index];
+        if (!remote_test) {
+            remote_test = new RemoteTest(data.test);
+            this.tests[data.test.index] = remote_test;
+        }
+        remote_test.update_state_from(data.test);
+        tests.notify_test_state(remote_test);
+    };
+
+    RemoteContext.prototype.test_done = function(data) {
+        var remote_test = this.tests[data.test.index];
+        remote_test.update_state_from(data.test);
+        remote_test.done();
+        tests.result(remote_test);
+    };
+
+    RemoteContext.prototype.remote_done = function(data) {
+        if (tests.status.status === null &&
+            data.status.status !== data.status.OK) {
+            tests.set_status(data.status.status, data.status.message, data.status.stack);
+        }
+
+        for (let assert of data.asserts) {
+            var record = new AssertRecord();
+            record.assert_name = assert.assert_name;
+            record.args = assert.args;
+            record.test = assert.test != null ? this.tests[assert.test.index] : null;
+            record.status = assert.status;
+            record.stack = assert.stack;
+            tests.asserts_run.push(record);
+        }
+
+        this.message_target.removeEventListener("message", this.message_handler);
+        this.running = false;
+
+        // If remote context is cross origin assigning to onerror is not
+        // possible, so silently catch those errors.
+        try {
+          this.remote.onerror = null;
+        } catch (e) {
+          // Ignore.
+        }
+
+        this.remote = null;
+        this.message_target = null;
+        if (this.doneResolve) {
+            this.doneResolve();
+        }
+
+        if (tests.all_done()) {
+            tests.complete();
+        }
+    };
+
+    RemoteContext.prototype.message_handlers = {
+        start: RemoteContext.prototype.start,
+        test_state: RemoteContext.prototype.test_state,
+        result: RemoteContext.prototype.test_done,
+        complete: RemoteContext.prototype.remote_done
+    };
+
+    /**
+     * @class
+     * Status of the overall harness
+     */
+    function TestsStatus()
+    {
+        /** The status code */
+        this.status = null;
+        /** Message in case of failure */
+        this.message = null;
+        /** Stack trace in case of an exception. */
+        this.stack = null;
+    }
+
+    /**
+     * Enum of possible harness statuses.
+     *
+     * :values:
+     *   - ``OK``
+     *   - ``ERROR``
+     *   - ``TIMEOUT``
+     *   - ``PRECONDITION_FAILED``
+     */
+    TestsStatus.statuses = {
+        OK:0,
+        ERROR:1,
+        TIMEOUT:2,
+        PRECONDITION_FAILED:3
+    };
+
+    TestsStatus.prototype = merge({}, TestsStatus.statuses);
+
+    TestsStatus.prototype.formats = {
+        0: "OK",
+        1: "Error",
+        2: "Timeout",
+        3: "Optional Feature Unsupported"
+    };
+
+    TestsStatus.prototype.structured_clone = function()
+    {
+        if (!this._structured_clone) {
+            var msg = this.message;
+            msg = msg ? String(msg) : msg;
+            this._structured_clone = merge({
+                status:this.status,
+                message:msg,
+                stack:this.stack
+            }, TestsStatus.statuses);
+        }
+        return this._structured_clone;
+    };
+
+    TestsStatus.prototype.format_status = function() {
+        return this.formats[this.status];
+    };
+
+    /**
+     * @class
+     * Record of an assert that ran.
+     *
+     * @param {Test} test - The test which ran the assert.
+     * @param {string} assert_name - The function name of the assert.
+     * @param {Any} args - The arguments passed to the assert function.
+     */
+    function AssertRecord(test, assert_name, args = []) {
+        /** Name of the assert that ran */
+        this.assert_name = assert_name;
+        /** Test that ran the assert */
+        this.test = test;
+        // Avoid keeping complex objects alive
+        /** Stringification of the arguments that were passed to the assert function */
+        this.args = args.map(x => format_value(x).replace(/\n/g, " "));
+        /** Status of the assert */
+        this.status = null;
+    }
+
+    AssertRecord.prototype.structured_clone = function() {
+        return {
+            assert_name: this.assert_name,
+            test: this.test ? this.test.structured_clone() : null,
+            args: this.args,
+            status: this.status,
+        };
+    };
+
+    function Tests()
+    {
+        this.tests = [];
+        this.num_pending = 0;
+
+        this.phases = {
+            INITIAL:0,
+            SETUP:1,
+            HAVE_TESTS:2,
+            HAVE_RESULTS:3,
+            COMPLETE:4
+        };
+        this.phase = this.phases.INITIAL;
+
+        this.properties = {};
+
+        this.wait_for_finish = false;
+        this.processing_callbacks = false;
+
+        this.allow_uncaught_exception = false;
+
+        this.file_is_test = false;
+        // This value is lazily initialized in order to avoid introducing a
+        // dependency on ECMAScript 2015 Promises to all tests.
+        this.promise_tests = null;
+        this.promise_setup_called = false;
+
+        this.timeout_multiplier = 1;
+        this.timeout_length = test_environment.test_timeout();
+        this.timeout_id = null;
+
+        this.start_callbacks = [];
+        this.test_state_callbacks = [];
+        this.test_done_callbacks = [];
+        this.all_done_callbacks = [];
+
+        this.hide_test_state = false;
+        this.pending_remotes = [];
+
+        this.current_test = null;
+        this.asserts_run = [];
+
+        // Track whether output is enabled, and thus whether or not we should
+        // track asserts.
+        //
+        // On workers we don't get properties set from testharnessreport.js, so
+        // we don't know whether or not to track asserts. To avoid the
+        // resulting performance hit, we assume we are not meant to. This means
+        // that assert tracking does not function on workers.
+        this.output = settings.output && 'document' in global_scope;
+
+        this.status = new TestsStatus();
+
+        var this_obj = this;
+
+        test_environment.add_on_loaded_callback(function() {
+            if (this_obj.all_done()) {
+                this_obj.complete();
+            }
+        });
+
+        this.set_timeout();
+    }
+
+    Tests.prototype.setup = function(func, properties)
+    {
+        if (this.phase >= this.phases.HAVE_RESULTS) {
+            return;
+        }
+
+        if (this.phase < this.phases.SETUP) {
+            this.phase = this.phases.SETUP;
+        }
+
+        this.properties = properties;
+
+        for (var p in properties) {
+            if (properties.hasOwnProperty(p)) {
+                var value = properties[p];
+                if (p == "allow_uncaught_exception") {
+                    this.allow_uncaught_exception = value;
+                } else if (p == "explicit_done" && value) {
+                    this.wait_for_finish = true;
+                } else if (p == "explicit_timeout" && value) {
+                    this.timeout_length = null;
+                    if (this.timeout_id)
+                    {
+                        clearTimeout(this.timeout_id);
+                    }
+                } else if (p == "single_test" && value) {
+                    this.set_file_is_test();
+                } else if (p == "timeout_multiplier") {
+                    this.timeout_multiplier = value;
+                    if (this.timeout_length) {
+                         this.timeout_length *= this.timeout_multiplier;
+                    }
+                } else if (p == "hide_test_state") {
+                    this.hide_test_state = value;
+                } else if (p == "output") {
+                    this.output = value;
+                } else if (p === "debug") {
+                    settings.debug = value;
+                }
+            }
+        }
+
+        if (func) {
+            try {
+                func();
+            } catch (e) {
+                this.status.status = e instanceof OptionalFeatureUnsupportedError ? this.status.PRECONDITION_FAILED : this.status.ERROR;
+                this.status.message = String(e);
+                this.status.stack = e.stack ? e.stack : null;
+                this.complete();
+            }
+        }
+        this.set_timeout();
+    };
+
+    Tests.prototype.set_file_is_test = function() {
+        if (this.tests.length > 0) {
+            throw new Error("Tried to set file as test after creating a test");
+        }
+        this.wait_for_finish = true;
+        this.file_is_test = true;
+        // Create the test, which will add it to the list of tests
+        tests.current_test = async_test();
+    };
+
+    Tests.prototype.set_status = function(status, message, stack)
+    {
+        this.status.status = status;
+        this.status.message = message;
+        this.status.stack = stack ? stack : null;
+    };
+
+    Tests.prototype.set_timeout = function() {
+        if (global_scope.clearTimeout) {
+            var this_obj = this;
+            clearTimeout(this.timeout_id);
+            if (this.timeout_length !== null) {
+                this.timeout_id = setTimeout(function() {
+                                                 this_obj.timeout();
+                                             }, this.timeout_length);
+            }
+        }
+    };
+
+    Tests.prototype.timeout = function() {
+        var test_in_cleanup = null;
+
+        if (this.status.status === null) {
+            forEach(this.tests,
+                    function(test) {
+                        // No more than one test is expected to be in the
+                        // "CLEANUP" phase at any time
+                        if (test.phase === test.phases.CLEANING) {
+                            test_in_cleanup = test;
+                        }
+
+                        test.phase = test.phases.COMPLETE;
+                    });
+
+            // Timeouts that occur while a test is in the "cleanup" phase
+            // indicate that some global state was not properly reverted. This
+            // invalidates the overall test execution, so the timeout should be
+            // reported as an error and cancel the execution of any remaining
+            // tests.
+            if (test_in_cleanup) {
+                this.status.status = this.status.ERROR;
+                this.status.message = "Timeout while running cleanup for " +
+                    "test named \"" + test_in_cleanup.name + "\".";
+                tests.status.stack = null;
+            } else {
+                this.status.status = this.status.TIMEOUT;
+            }
+        }
+
+        this.complete();
+    };
+
+    Tests.prototype.end_wait = function()
+    {
+        this.wait_for_finish = false;
+        if (this.all_done()) {
+            this.complete();
+        }
+    };
+
+    Tests.prototype.push = function(test)
+    {
+        if (this.phase < this.phases.HAVE_TESTS) {
+            this.start();
+        }
+        this.num_pending++;
+        test.index = this.tests.push(test);
+        this.notify_test_state(test);
+    };
+
+    Tests.prototype.notify_test_state = function(test) {
+        var this_obj = this;
+        forEach(this.test_state_callbacks,
+                function(callback) {
+                    callback(test, this_obj);
+                });
+    };
+
+    Tests.prototype.all_done = function() {
+        return (this.tests.length > 0 || this.pending_remotes.length > 0) &&
+                test_environment.all_loaded &&
+                (this.num_pending === 0 || this.is_aborted) && !this.wait_for_finish &&
+                !this.processing_callbacks &&
+                !this.pending_remotes.some(function(w) { return w.running; });
+    };
+
+    Tests.prototype.start = function() {
+        this.phase = this.phases.HAVE_TESTS;
+        this.notify_start();
+    };
+
+    Tests.prototype.notify_start = function() {
+        var this_obj = this;
+        forEach (this.start_callbacks,
+                 function(callback)
+                 {
+                     callback(this_obj.properties);
+                 });
+    };
+
+    Tests.prototype.result = function(test)
+    {
+        // If the harness has already transitioned beyond the `HAVE_RESULTS`
+        // phase, subsequent tests should not cause it to revert.
+        if (this.phase <= this.phases.HAVE_RESULTS) {
+            this.phase = this.phases.HAVE_RESULTS;
+        }
+        this.num_pending--;
+        this.notify_result(test);
+    };
+
+    Tests.prototype.notify_result = function(test) {
+        var this_obj = this;
+        this.processing_callbacks = true;
+        forEach(this.test_done_callbacks,
+                function(callback)
+                {
+                    callback(test, this_obj);
+                });
+        this.processing_callbacks = false;
+        if (this_obj.all_done()) {
+            this_obj.complete();
+        }
+    };
+
+    Tests.prototype.complete = function() {
+        if (this.phase === this.phases.COMPLETE) {
+            return;
+        }
+        var this_obj = this;
+        var all_complete = function() {
+            this_obj.phase = this_obj.phases.COMPLETE;
+            this_obj.notify_complete();
+        };
+        var incomplete = filter(this.tests,
+                                function(test) {
+                                    return test.phase < test.phases.COMPLETE;
+                                });
+
+        /**
+         * To preserve legacy behavior, overall test completion must be
+         * signaled synchronously.
+         */
+        if (incomplete.length === 0) {
+            all_complete();
+            return;
+        }
+
+        all_async(incomplete,
+                  function(test, testDone)
+                  {
+                      if (test.phase === test.phases.INITIAL) {
+                          test.phase = test.phases.COMPLETE;
+                          testDone();
+                      } else {
+                          add_test_done_callback(test, testDone);
+                          test.cleanup();
+                      }
+                  },
+                  all_complete);
+    };
+
+    Tests.prototype.set_assert = function(assert_name, args) {
+        this.asserts_run.push(new AssertRecord(this.current_test, assert_name, args))
+    }
+
+    Tests.prototype.set_assert_status = function(index, status, stack) {
+        let assert_record = this.asserts_run[index];
+        assert_record.status = status;
+        assert_record.stack = stack;
+    }
+
+    /**
+     * Update the harness status to reflect an unrecoverable harness error that
+     * should cancel all further testing. Update all previously-defined tests
+     * which have not yet started to indicate that they will not be executed.
+     */
+    Tests.prototype.abort = function() {
+        this.status.status = this.status.ERROR;
+        this.is_aborted = true;
+
+        forEach(this.tests,
+                function(test) {
+                    if (test.phase === test.phases.INITIAL) {
+                        test.phase = test.phases.COMPLETE;
+                    }
+                });
+    };
+
+    /*
+     * Determine if any tests share the same `name` property. Return an array
+     * containing the names of any such duplicates.
+     */
+    Tests.prototype.find_duplicates = function() {
+        var names = Object.create(null);
+        var duplicates = [];
+
+        forEach (this.tests,
+                 function(test)
+                 {
+                     if (test.name in names && duplicates.indexOf(test.name) === -1) {
+                        duplicates.push(test.name);
+                     }
+                     names[test.name] = true;
+                 });
+
+        return duplicates;
+    };
+
+    function code_unit_str(char) {
+        return 'U+' + char.charCodeAt(0).toString(16);
+    }
+
+    function sanitize_unpaired_surrogates(str) {
+        return str.replace(
+            /([\ud800-\udbff]+)(?![\udc00-\udfff])|(^|[^\ud800-\udbff])([\udc00-\udfff]+)/g,
+            function(_, low, prefix, high) {
+                var output = prefix || "";  // prefix may be undefined
+                var string = low || high;  // only one of these alternates can match
+                for (var i = 0; i < string.length; i++) {
+                    output += code_unit_str(string[i]);
+                }
+                return output;
+            });
+    }
+
+    function sanitize_all_unpaired_surrogates(tests) {
+        forEach (tests,
+                 function (test)
+                 {
+                     var sanitized = sanitize_unpaired_surrogates(test.name);
+
+                     if (test.name !== sanitized) {
+                         test.name = sanitized;
+                         delete test._structured_clone;
+                     }
+                 });
+    }
+
+    Tests.prototype.notify_complete = function() {
+        var this_obj = this;
+        var duplicates;
+
+        if (this.status.status === null) {
+            duplicates = this.find_duplicates();
+
+            // Some transports adhere to UTF-8's restriction on unpaired
+            // surrogates. Sanitize the titles so that the results can be
+            // consistently sent via all transports.
+            sanitize_all_unpaired_surrogates(this.tests);
+
+            // Test names are presumed to be unique within test files--this
+            // allows consumers to use them for identification purposes.
+            // Duplicated names violate this expectation and should therefore
+            // be reported as an error.
+            if (duplicates.length) {
+                this.status.status = this.status.ERROR;
+                this.status.message =
+                   duplicates.length + ' duplicate test name' +
+                   (duplicates.length > 1 ? 's' : '') + ': "' +
+                   duplicates.join('", "') + '"';
+            } else {
+                this.status.status = this.status.OK;
+            }
+        }
+
+        forEach (this.all_done_callbacks,
+                 function(callback)
+                 {
+                     callback(this_obj.tests, this_obj.status, this_obj.asserts_run);
+                 });
+    };
+
+    /*
+     * Constructs a RemoteContext that tracks tests from a specific worker.
+     */
+    Tests.prototype.create_remote_worker = function(worker) {
+        var message_port;
+
+        if (is_service_worker(worker)) {
+            message_port = navigator.serviceWorker;
+            worker.postMessage({type: "connect"});
+        } else if (is_shared_worker(worker)) {
+            message_port = worker.port;
+            message_port.start();
+        } else {
+            message_port = worker;
+        }
+
+        return new RemoteContext(worker, message_port);
+    };
+
+    /*
+     * Constructs a RemoteContext that tracks tests from a specific window.
+     */
+    Tests.prototype.create_remote_window = function(remote) {
+        remote.postMessage({type: "getmessages"}, "*");
+        return new RemoteContext(
+            remote,
+            window,
+            function(msg) {
+                return msg.source === remote;
+            }
+        );
+    };
+
+    Tests.prototype.fetch_tests_from_worker = function(worker) {
+        if (this.phase >= this.phases.COMPLETE) {
+            return;
+        }
+
+        var remoteContext = this.create_remote_worker(worker);
+        this.pending_remotes.push(remoteContext);
+        return remoteContext.done;
+    };
+
+    /**
+     * Get test results from a worker and include them in the current test.
+     *
+     * @param {Worker|SharedWorker|ServiceWorker|MessagePort} port -
+     * Either a worker object or a port connected to a worker which is
+     * running tests..
+     * @returns {Promise} - A promise that's resolved once all the remote tests are complete.
+     */
+    function fetch_tests_from_worker(port) {
+        return tests.fetch_tests_from_worker(port);
+    }
+    expose(fetch_tests_from_worker, 'fetch_tests_from_worker');
+
+    Tests.prototype.fetch_tests_from_window = function(remote) {
+        if (this.phase >= this.phases.COMPLETE) {
+            return;
+        }
+
+        var remoteContext = this.create_remote_window(remote);
+        this.pending_remotes.push(remoteContext);
+        return remoteContext.done;
+    };
+
+    /**
+     * Aggregate tests from separate windows or iframes
+     * into the current document as if they were all part of the same test file.
+     *
+     * The document of the second window (or iframe) should include
+     * ``testharness.js``, but not ``testharnessreport.js``, and use
+     * :js:func:`test`, :js:func:`async_test`, and :js:func:`promise_test` in
+     * the usual manner.
+     *
+     * @param {Window} window - The window to fetch tests from.
+     */
+    function fetch_tests_from_window(window) {
+        return tests.fetch_tests_from_window(window);
+    }
+    expose(fetch_tests_from_window, 'fetch_tests_from_window');
+
+    /**
+     * Get test results from a shadow realm and include them in the current test.
+     *
+     * @param {ShadowRealm} realm - A shadow realm also running the test harness
+     * @returns {Promise} - A promise that's resolved once all the remote tests are complete.
+     */
+    function fetch_tests_from_shadow_realm(realm) {
+        var chan = new MessageChannel();
+        function receiveMessage(msg_json) {
+            chan.port1.postMessage(JSON.parse(msg_json));
+        }
+        var done = tests.fetch_tests_from_worker(chan.port2);
+        realm.evaluate("begin_shadow_realm_tests")(receiveMessage);
+        chan.port2.start();
+        return done;
+    }
+    expose(fetch_tests_from_shadow_realm, 'fetch_tests_from_shadow_realm');
+
+    /**
+     * Begin running tests in this shadow realm test harness.
+     *
+     * To be called after all tests have been loaded; it is an error to call
+     * this more than once or in a non-Shadow Realm environment
+     *
+     * @param {Function} postMessage - A function to send test updates to the
+     * incubating realm-- accepts JSON-encoded messages in the format used by
+     * RemoteContext
+     */
+    function begin_shadow_realm_tests(postMessage) {
+        if (!(test_environment instanceof ShadowRealmTestEnvironment)) {
+            throw new Error("begin_shadow_realm_tests called in non-Shadow Realm environment");
+        }
+
+        test_environment.begin(function (msg) {
+            postMessage(JSON.stringify(msg));
+        });
+    }
+    expose(begin_shadow_realm_tests, 'begin_shadow_realm_tests');
+
+    /**
+     * Timeout the tests.
+     *
+     * This only has an effect when ``explicit_timeout`` has been set
+     * in :js:func:`setup`. In other cases any call is a no-op.
+     *
+     */
+    function timeout() {
+        if (tests.timeout_length === null) {
+            tests.timeout();
+        }
+    }
+    expose(timeout, 'timeout');
+
+    /**
+     * Add a callback that's triggered when the first :js:class:`Test` is created.
+     *
+     * @param {Function} callback - Callback function. This is called
+     * without arguments.
+     */
+    function add_start_callback(callback) {
+        tests.start_callbacks.push(callback);
+    }
+
+    /**
+     * Add a callback that's triggered when a test state changes.
+     *
+     * @param {Function} callback - Callback function, called with the
+     * :js:class:`Test` as the only argument.
+     */
+    function add_test_state_callback(callback) {
+        tests.test_state_callbacks.push(callback);
+    }
+
+    /**
+     * Add a callback that's triggered when a test result is received.
+     *
+     * @param {Function} callback - Callback function, called with the
+     * :js:class:`Test` as the only argument.
+     */
+    function add_result_callback(callback) {
+        tests.test_done_callbacks.push(callback);
+    }
+
+    /**
+     * Add a callback that's triggered when all tests are complete.
+     *
+     * @param {Function} callback - Callback function, called with an
+     * array of :js:class:`Test` objects, a :js:class:`TestsStatus`
+     * object and an array of :js:class:`AssertRecord` objects. If the
+     * debug setting is ``false`` the final argument will be an empty
+     * array.
+     *
+     * For performance reasons asserts are only tracked when the debug
+     * setting is ``true``. In other cases the array of asserts will be
+     * empty.
+     */
+    function add_completion_callback(callback) {
+        tests.all_done_callbacks.push(callback);
+    }
+
+    expose(add_start_callback, 'add_start_callback');
+    expose(add_test_state_callback, 'add_test_state_callback');
+    expose(add_result_callback, 'add_result_callback');
+    expose(add_completion_callback, 'add_completion_callback');
+
+    function remove(array, item) {
+        var index = array.indexOf(item);
+        if (index > -1) {
+            array.splice(index, 1);
+        }
+    }
+
+    function remove_start_callback(callback) {
+        remove(tests.start_callbacks, callback);
+    }
+
+    function remove_test_state_callback(callback) {
+        remove(tests.test_state_callbacks, callback);
+    }
+
+    function remove_result_callback(callback) {
+        remove(tests.test_done_callbacks, callback);
+    }
+
+    function remove_completion_callback(callback) {
+       remove(tests.all_done_callbacks, callback);
+    }
+
+    /*
+     * Output listener
+    */
+
+    function Output() {
+        this.output_document = document;
+        this.output_node = null;
+        this.enabled = settings.output;
+        this.phase = this.INITIAL;
+    }
+
+    Output.prototype.INITIAL = 0;
+    Output.prototype.STARTED = 1;
+    Output.prototype.HAVE_RESULTS = 2;
+    Output.prototype.COMPLETE = 3;
+
+    Output.prototype.setup = function(properties) {
+        if (this.phase > this.INITIAL) {
+            return;
+        }
+
+        //If output is disabled in testharnessreport.js the test shouldn't be
+        //able to override that
+        this.enabled = this.enabled && (properties.hasOwnProperty("output") ?
+                                        properties.output : settings.output);
+    };
+
+    Output.prototype.init = function(properties) {
+        if (this.phase >= this.STARTED) {
+            return;
+        }
+        if (properties.output_document) {
+            this.output_document = properties.output_document;
+        } else {
+            this.output_document = document;
+        }
+        this.phase = this.STARTED;
+    };
+
+    Output.prototype.resolve_log = function() {
+        var output_document;
+        if (this.output_node) {
+            return;
+        }
+        if (typeof this.output_document === "function") {
+            output_document = this.output_document.apply(undefined);
+        } else {
+            output_document = this.output_document;
+        }
+        if (!output_document) {
+            return;
+        }
+        var node = output_document.getElementById("log");
+        if (!node) {
+            if (output_document.readyState === "loading") {
+                return;
+            }
+            node = output_document.createElementNS("http://www.w3.org/1999/xhtml", "div");
+            node.id = "log";
+            if (output_document.body) {
+                output_document.body.appendChild(node);
+            } else {
+                var root = output_document.documentElement;
+                var is_html = (root &&
+                               root.namespaceURI == "http://www.w3.org/1999/xhtml" &&
+                               root.localName == "html");
+                var is_svg = (output_document.defaultView &&
+                              "SVGSVGElement" in output_document.defaultView &&
+                              root instanceof output_document.defaultView.SVGSVGElement);
+                if (is_svg) {
+                    var foreignObject = output_document.createElementNS("http://www.w3.org/2000/svg", "foreignObject");
+                    foreignObject.setAttribute("width", "100%");
+                    foreignObject.setAttribute("height", "100%");
+                    root.appendChild(foreignObject);
+                    foreignObject.appendChild(node);
+                } else if (is_html) {
+                    root.appendChild(output_document.createElementNS("http://www.w3.org/1999/xhtml", "body"))
+                        .appendChild(node);
+                } else {
+                    root.appendChild(node);
+                }
+            }
+        }
+        this.output_document = output_document;
+        this.output_node = node;
+    };
+
+    Output.prototype.show_status = function() {
+        if (this.phase < this.STARTED) {
+            this.init({});
+        }
+        if (!this.enabled || this.phase === this.COMPLETE) {
+            return;
+        }
+        this.resolve_log();
+        if (this.phase < this.HAVE_RESULTS) {
+            this.phase = this.HAVE_RESULTS;
+        }
+        var done_count = tests.tests.length - tests.num_pending;
+        if (this.output_node && !tests.hide_test_state) {
+            if (done_count < 100 ||
+                (done_count < 1000 && done_count % 100 === 0) ||
+                done_count % 1000 === 0) {
+                this.output_node.textContent = "Running, " +
+                    done_count + " complete, " +
+                    tests.num_pending + " remain";
+            }
+        }
+    };
+
+    Output.prototype.show_results = function (tests, harness_status, asserts_run) {
+        if (this.phase >= this.COMPLETE) {
+            return;
+        }
+        if (!this.enabled) {
+            return;
+        }
+        if (!this.output_node) {
+            this.resolve_log();
+        }
+        this.phase = this.COMPLETE;
+
+        var log = this.output_node;
+        if (!log) {
+            return;
+        }
+        var output_document = this.output_document;
+
+        while (log.lastChild) {
+            log.removeChild(log.lastChild);
+        }
+
+        var stylesheet = output_document.createElementNS(xhtml_ns, "style");
+        stylesheet.textContent = stylesheetContent;
+        var heads = output_document.getElementsByTagName("head");
+        if (heads.length) {
+            heads[0].appendChild(stylesheet);
+        }
+
+        var status_number = {};
+        forEach(tests,
+                function(test) {
+                    var status = test.format_status();
+                    if (status_number.hasOwnProperty(status)) {
+                        status_number[status] += 1;
+                    } else {
+                        status_number[status] = 1;
+                    }
+                });
+
+        function status_class(status)
+        {
+            return status.replace(/\s/g, '').toLowerCase();
+        }
+
+        var summary_template = ["section", {"id":"summary"},
+                                ["h2", {}, "Summary"],
+                                function()
+                                {
+                                    var status = harness_status.format_status();
+                                    var rv = [["section", {},
+                                               ["p", {},
+                                                "Harness status: ",
+                                                ["span", {"class":status_class(status)},
+                                                 status
+                                                ],
+                                               ],
+                                               ["button",
+                                                {"onclick": "let evt = new Event('__test_restart'); " +
+                                                 "let canceled = !window.dispatchEvent(evt);" +
+                                                 "if (!canceled) { location.reload() }"},
+                                                "Rerun"]
+                                              ]];
+
+                                    if (harness_status.status === harness_status.ERROR) {
+                                        rv[0].push(["pre", {}, harness_status.message]);
+                                        if (harness_status.stack) {
+                                            rv[0].push(["pre", {}, harness_status.stack]);
+                                        }
+                                    }
+                                    return rv;
+                                },
+                                ["p", {}, "Found ${num_tests} tests"],
+                                function() {
+                                    var rv = [["div", {}]];
+                                    var i = 0;
+                                    while (Test.prototype.status_formats.hasOwnProperty(i)) {
+                                        if (status_number.hasOwnProperty(Test.prototype.status_formats[i])) {
+                                            var status = Test.prototype.status_formats[i];
+                                            rv[0].push(["div", {},
+                                                        ["label", {},
+                                                         ["input", {type:"checkbox", checked:"checked"}],
+                                                         status_number[status] + " ",
+                                                         ["span", {"class":status_class(status)}, status]]]);
+                                        }
+                                        i++;
+                                    }
+                                    return rv;
+                                },
+                               ];
+
+        log.appendChild(render(summary_template, {num_tests:tests.length}, output_document));
+
+        forEach(output_document.querySelectorAll("section#summary label"),
+                function(element)
+                {
+                    on_event(element, "click",
+                             function(e)
+                             {
+                                 if (output_document.getElementById("results") === null) {
+                                     e.preventDefault();
+                                     return;
+                                 }
+                                 var result_class = element.querySelector("span[class]").getAttribute("class");
+                                 var style_element = output_document.querySelector("style#hide-" + result_class);
+                                 var input_element = element.querySelector("input");
+                                 if (!style_element && !input_element.checked) {
+                                     style_element = output_document.createElementNS(xhtml_ns, "style");
+                                     style_element.id = "hide-" + result_class;
+                                     style_element.textContent = "table#results > tbody > tr.overall-"+result_class+"{display:none}";
+                                     output_document.body.appendChild(style_element);
+                                 } else if (style_element && input_element.checked) {
+                                     style_element.parentNode.removeChild(style_element);
+                                 }
+                             });
+                });
+
+        // This use of innerHTML plus manual escaping is not recommended in
+        // general, but is necessary here for performance.  Using textContent
+        // on each individual <td> adds tens of seconds of execution time for
+        // large test suites (tens of thousands of tests).
+        function escape_html(s)
+        {
+            return s.replace(/\&/g, "&amp;")
+                .replace(/</g, "&lt;")
+                .replace(/"/g, "&quot;")
+                .replace(/'/g, "&#39;");
+        }
+
+        function has_assertions()
+        {
+            for (var i = 0; i < tests.length; i++) {
+                if (tests[i].properties.hasOwnProperty("assert")) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        function get_assertion(test)
+        {
+            if (test.properties.hasOwnProperty("assert")) {
+                if (Array.isArray(test.properties.assert)) {
+                    return test.properties.assert.join(' ');
+                }
+                return test.properties.assert;
+            }
+            return '';
+        }
+
+        var asserts_run_by_test = new Map();
+        asserts_run.forEach(assert => {
+            if (!asserts_run_by_test.has(assert.test)) {
+                asserts_run_by_test.set(assert.test, []);
+            }
+            asserts_run_by_test.get(assert.test).push(assert);
+        });
+
+        function get_asserts_output(test) {
+            var asserts = asserts_run_by_test.get(test);
+            if (!asserts) {
+                return "No asserts ran";
+            }
+            rv = "<table>";
+            rv += asserts.map(assert => {
+                var output_fn = "<strong>" + escape_html(assert.assert_name) + "</strong>(";
+                var prefix_len = output_fn.length;
+                var output_args = assert.args;
+                var output_len = output_args.reduce((prev, current) => prev+current, prefix_len);
+                if (output_len[output_len.length - 1] > 50) {
+                    output_args = output_args.map((x, i) =>
+                    (i > 0 ? "  ".repeat(prefix_len) : "" )+ x + (i < output_args.length - 1 ? ",\n" : ""));
+                } else {
+                    output_args = output_args.map((x, i) => x + (i < output_args.length - 1 ? ", " : ""));
+                }
+                output_fn += escape_html(output_args.join(""));
+                output_fn += ')';
+                var output_location;
+                if (assert.stack) {
+                    output_location = assert.stack.split("\n", 1)[0].replace(/@?\w+:\/\/[^ "\/]+(?::\d+)?/g, " ");
+                }
+                return "<tr class='overall-" +
+                    status_class(Test.prototype.status_formats[assert.status]) + "'>" +
+                    "<td class='" +
+                    status_class(Test.prototype.status_formats[assert.status]) + "'>" +
+                    Test.prototype.status_formats[assert.status] + "</td>" +
+                    "<td><pre>" +
+                    output_fn +
+                    (output_location ? "\n" + escape_html(output_location) : "") +
+                    "</pre></td></tr>";
+            }
+            ).join("\n");
+            rv += "</table>";
+            return rv;
+        }
+
+        log.appendChild(document.createElementNS(xhtml_ns, "section"));
+        var assertions = has_assertions();
+        var html = "<h2>Details</h2><table id='results' " + (assertions ? "class='assertions'" : "" ) + ">" +
+            "<thead><tr><th>Result</th><th>Test Name</th>" +
+            (assertions ? "<th>Assertion</th>" : "") +
+            "<th>Message</th></tr></thead>" +
+            "<tbody>";
+        for (var i = 0; i < tests.length; i++) {
+            var test = tests[i];
+            html += '<tr class="overall-' +
+                status_class(test.format_status()) +
+                '">' +
+                '<td class="' +
+                status_class(test.format_status()) +
+                '">' +
+                test.format_status() +
+                "</td><td>" +
+                escape_html(test.name) +
+                "</td><td>" +
+                (assertions ? escape_html(get_assertion(test)) + "</td><td>" : "") +
+                escape_html(test.message ? tests[i].message : " ") +
+                (tests[i].stack ? "<pre>" +
+                 escape_html(tests[i].stack) +
+                 "</pre>": "");
+            if (!(test instanceof RemoteTest)) {
+                 html += "<details><summary>Asserts run</summary>" + get_asserts_output(test) + "</details>"
+            }
+            html += "</td></tr>";
+        }
+        html += "</tbody></table>";
+        try {
+            log.lastChild.innerHTML = html;
+        } catch (e) {
+            log.appendChild(document.createElementNS(xhtml_ns, "p"))
+               .textContent = "Setting innerHTML for the log threw an exception.";
+            log.appendChild(document.createElementNS(xhtml_ns, "pre"))
+               .textContent = html;
+        }
+    };
+
+    /*
+     * Template code
+     *
+     * A template is just a JavaScript structure. An element is represented as:
+     *
+     * [tag_name, {attr_name:attr_value}, child1, child2]
+     *
+     * the children can either be strings (which act like text nodes), other templates or
+     * functions (see below)
+     *
+     * A text node is represented as
+     *
+     * ["{text}", value]
+     *
+     * String values have a simple substitution syntax; ${foo} represents a variable foo.
+     *
+     * It is possible to embed logic in templates by using a function in a place where a
+     * node would usually go. The function must either return part of a template or null.
+     *
+     * In cases where a set of nodes are required as output rather than a single node
+     * with children it is possible to just use a list
+     * [node1, node2, node3]
+     *
+     * Usage:
+     *
+     * render(template, substitutions) - take a template and an object mapping
+     * variable names to parameters and return either a DOM node or a list of DOM nodes
+     *
+     * substitute(template, substitutions) - take a template and variable mapping object,
+     * make the variable substitutions and return the substituted template
+     *
+     */
+
+    function is_single_node(template)
+    {
+        return typeof template[0] === "string";
+    }
+
+    function substitute(template, substitutions)
+    {
+        if (typeof template === "function") {
+            var replacement = template(substitutions);
+            if (!replacement) {
+                return null;
+            }
+
+            return substitute(replacement, substitutions);
+        }
+
+        if (is_single_node(template)) {
+            return substitute_single(template, substitutions);
+        }
+
+        return filter(map(template, function(x) {
+                              return substitute(x, substitutions);
+                          }), function(x) {return x !== null;});
+    }
+
+    function substitute_single(template, substitutions)
+    {
+        var substitution_re = /\$\{([^ }]*)\}/g;
+
+        function do_substitution(input) {
+            var components = input.split(substitution_re);
+            var rv = [];
+            for (var i = 0; i < components.length; i += 2) {
+                rv.push(components[i]);
+                if (components[i + 1]) {
+                    rv.push(String(substitutions[components[i + 1]]));
+                }
+            }
+            return rv;
+        }
+
+        function substitute_attrs(attrs, rv)
+        {
+            rv[1] = {};
+            for (var name in template[1]) {
+                if (attrs.hasOwnProperty(name)) {
+                    var new_name = do_substitution(name).join("");
+                    var new_value = do_substitution(attrs[name]).join("");
+                    rv[1][new_name] = new_value;
+                }
+            }
+        }
+
+        function substitute_children(children, rv)
+        {
+            for (var i = 0; i < children.length; i++) {
+                if (children[i] instanceof Object) {
+                    var replacement = substitute(children[i], substitutions);
+                    if (replacement !== null) {
+                        if (is_single_node(replacement)) {
+                            rv.push(replacement);
+                        } else {
+                            extend(rv, replacement);
+                        }
+                    }
+                } else {
+                    extend(rv, do_substitution(String(children[i])));
+                }
+            }
+            return rv;
+        }
+
+        var rv = [];
+        rv.push(do_substitution(String(template[0])).join(""));
+
+        if (template[0] === "{text}") {
+            substitute_children(template.slice(1), rv);
+        } else {
+            substitute_attrs(template[1], rv);
+            substitute_children(template.slice(2), rv);
+        }
+
+        return rv;
+    }
+
+    function make_dom_single(template, doc)
+    {
+        var output_document = doc || document;
+        var element;
+        if (template[0] === "{text}") {
+            element = output_document.createTextNode("");
+            for (var i = 1; i < template.length; i++) {
+                element.data += template[i];
+            }
+        } else {
+            element = output_document.createElementNS(xhtml_ns, template[0]);
+            for (var name in template[1]) {
+                if (template[1].hasOwnProperty(name)) {
+                    element.setAttribute(name, template[1][name]);
+                }
+            }
+            for (var i = 2; i < template.length; i++) {
+                if (template[i] instanceof Object) {
+                    var sub_element = make_dom(template[i]);
+                    element.appendChild(sub_element);
+                } else {
+                    var text_node = output_document.createTextNode(template[i]);
+                    element.appendChild(text_node);
+                }
+            }
+        }
+
+        return element;
+    }
+
+    function make_dom(template, substitutions, output_document)
+    {
+        if (is_single_node(template)) {
+            return make_dom_single(template, output_document);
+        }
+
+        return map(template, function(x) {
+                       return make_dom_single(x, output_document);
+                   });
+    }
+
+    function render(template, substitutions, output_document)
+    {
+        return make_dom(substitute(template, substitutions), output_document);
+    }
+
+    /*
+     * Utility functions
+     */
+    function assert(expected_true, function_name, description, error, substitutions)
+    {
+        if (expected_true !== true) {
+            var msg = make_message(function_name, description,
+                                   error, substitutions);
+            throw new AssertionError(msg);
+        }
+    }
+
+    /**
+     * @class
+     * Exception type that represents a failing assert.
+     *
+     * @param {string} message - Error message.
+     */
+    function AssertionError(message)
+    {
+        if (typeof message == "string") {
+            message = sanitize_unpaired_surrogates(message);
+        }
+        this.message = message;
+        this.stack = get_stack();
+    }
+    expose(AssertionError, "AssertionError");
+
+    AssertionError.prototype = Object.create(Error.prototype);
+
+    const get_stack = function() {
+        var stack = new Error().stack;
+
+        // 'Error.stack' is not supported in all browsers/versions
+        if (!stack) {
+            return "(Stack trace unavailable)";
+        }
+
+        var lines = stack.split("\n");
+
+        // Create a pattern to match stack frames originating within testharness.js.  These include the
+        // script URL, followed by the line/col (e.g., '/resources/testharness.js:120:21').
+        // Escape the URL per http://stackoverflow.com/questions/3561493/is-there-a-regexp-escape-function-in-javascript
+        // in case it contains RegExp characters.
+        var script_url = get_script_url();
+        var re_text = script_url ? script_url.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&') : "\\btestharness.js";
+        var re = new RegExp(re_text + ":\\d+:\\d+");
+
+        // Some browsers include a preamble that specifies the type of the error object.  Skip this by
+        // advancing until we find the first stack frame originating from testharness.js.
+        var i = 0;
+        while (!re.test(lines[i]) && i < lines.length) {
+            i++;
+        }
+
+        // Then skip the top frames originating from testharness.js to begin the stack at the test code.
+        while (re.test(lines[i]) && i < lines.length) {
+            i++;
+        }
+
+        // Paranoid check that we didn't skip all frames.  If so, return the original stack unmodified.
+        if (i >= lines.length) {
+            return stack;
+        }
+
+        return lines.slice(i).join("\n");
+    }
+
+    function OptionalFeatureUnsupportedError(message)
+    {
+        AssertionError.call(this, message);
+    }
+    OptionalFeatureUnsupportedError.prototype = Object.create(AssertionError.prototype);
+    expose(OptionalFeatureUnsupportedError, "OptionalFeatureUnsupportedError");
+
+    function make_message(function_name, description, error, substitutions)
+    {
+        for (var p in substitutions) {
+            if (substitutions.hasOwnProperty(p)) {
+                substitutions[p] = format_value(substitutions[p]);
+            }
+        }
+        var node_form = substitute(["{text}", "${function_name}: ${description}" + error],
+                                   merge({function_name:function_name,
+                                          description:(description?description + " ":"")},
+                                          substitutions));
+        return node_form.slice(1).join("");
+    }
+
+    function filter(array, callable, thisObj) {
+        var rv = [];
+        for (var i = 0; i < array.length; i++) {
+            if (array.hasOwnProperty(i)) {
+                var pass = callable.call(thisObj, array[i], i, array);
+                if (pass) {
+                    rv.push(array[i]);
+                }
+            }
+        }
+        return rv;
+    }
+
+    function map(array, callable, thisObj)
+    {
+        var rv = [];
+        rv.length = array.length;
+        for (var i = 0; i < array.length; i++) {
+            if (array.hasOwnProperty(i)) {
+                rv[i] = callable.call(thisObj, array[i], i, array);
+            }
+        }
+        return rv;
+    }
+
+    function extend(array, items)
+    {
+        Array.prototype.push.apply(array, items);
+    }
+
+    function forEach(array, callback, thisObj)
+    {
+        for (var i = 0; i < array.length; i++) {
+            if (array.hasOwnProperty(i)) {
+                callback.call(thisObj, array[i], i, array);
+            }
+        }
+    }
+
+    /**
+     * Immediately invoke a "iteratee" function with a series of values in
+     * parallel and invoke a final "done" function when all of the "iteratee"
+     * invocations have signaled completion.
+     *
+     * If all callbacks complete synchronously (or if no callbacks are
+     * specified), the ``done_callback`` will be invoked synchronously. It is the
+     * responsibility of the caller to ensure asynchronicity in cases where
+     * that is desired.
+     *
+     * @param {array} value Zero or more values to use in the invocation of
+     *                      ``iter_callback``
+     * @param {function} iter_callback A function that will be invoked
+     *                                 once for each of the values min
+     *                                 ``value``. Two arguments will
+     *                                 be available in each
+     *                                 invocation: the value from
+     *                                 ``value`` and a function that
+     *                                 must be invoked to signal
+     *                                 completion
+     * @param {function} done_callback A function that will be invoked after
+     *                                 all operations initiated by the
+     *                                 ``iter_callback`` function have signaled
+     *                                 completion
+     */
+    function all_async(values, iter_callback, done_callback)
+    {
+        var remaining = values.length;
+
+        if (remaining === 0) {
+            done_callback();
+        }
+
+        forEach(values,
+                function(element) {
+                    var invoked = false;
+                    var elDone = function() {
+                        if (invoked) {
+                            return;
+                        }
+
+                        invoked = true;
+                        remaining -= 1;
+
+                        if (remaining === 0) {
+                            done_callback();
+                        }
+                    };
+
+                    iter_callback(element, elDone);
+                });
+    }
+
+    function merge(a,b)
+    {
+        var rv = {};
+        var p;
+        for (p in a) {
+            rv[p] = a[p];
+        }
+        for (p in b) {
+            rv[p] = b[p];
+        }
+        return rv;
+    }
+
+    function expose(object, name)
+    {
+        var components = name.split(".");
+        var target = global_scope;
+        for (var i = 0; i < components.length - 1; i++) {
+            if (!(components[i] in target)) {
+                target[components[i]] = {};
+            }
+            target = target[components[i]];
+        }
+        target[components[components.length - 1]] = object;
+    }
+
+    function is_same_origin(w) {
+        try {
+            'random_prop' in w;
+            return true;
+        } catch (e) {
+            return false;
+        }
+    }
+
+    /** Returns the 'src' URL of the first <script> tag in the page to include the file 'testharness.js'. */
+    function get_script_url()
+    {
+        if (!('document' in global_scope)) {
+            return undefined;
+        }
+
+        var scripts = document.getElementsByTagName("script");
+        for (var i = 0; i < scripts.length; i++) {
+            var src;
+            if (scripts[i].src) {
+                src = scripts[i].src;
+            } else if (scripts[i].href) {
+                //SVG case
+                src = scripts[i].href.baseVal;
+            }
+
+            var matches = src && src.match(/^(.*\/|)testharness\.js$/);
+            if (matches) {
+                return src;
+            }
+        }
+        return undefined;
+    }
+
+    /** Returns the <title> or filename or "Untitled" */
+    function get_title()
+    {
+        if ('document' in global_scope) {
+            //Don't use document.title to work around an Opera/Presto bug in XHTML documents
+            var title = document.getElementsByTagName("title")[0];
+            if (title && title.firstChild && title.firstChild.data) {
+                return title.firstChild.data;
+            }
+        }
+        if ('META_TITLE' in global_scope && META_TITLE) {
+            return META_TITLE;
+        }
+        if ('location' in global_scope && 'pathname' in location) {
+            return location.pathname.substring(location.pathname.lastIndexOf('/') + 1, location.pathname.indexOf('.'));
+        }
+        return "Untitled";
+    }
+
+    /**
+     * Setup globals
+     */
+
+    var tests = new Tests();
+
+    if (global_scope.addEventListener) {
+        var error_handler = function(error, message, stack) {
+            var optional_unsupported = error instanceof OptionalFeatureUnsupportedError;
+            if (tests.file_is_test) {
+                var test = tests.tests[0];
+                if (test.phase >= test.phases.HAS_RESULT) {
+                    return;
+                }
+                var status = optional_unsupported ? test.PRECONDITION_FAILED : test.FAIL;
+                test.set_status(status, message, stack);
+                test.phase = test.phases.HAS_RESULT;
+            } else if (!tests.allow_uncaught_exception) {
+                var status = optional_unsupported ? tests.status.PRECONDITION_FAILED : tests.status.ERROR;
+                tests.status.status = status;
+                tests.status.message = message;
+                tests.status.stack = stack;
+            }
+
+            // Do not transition to the "complete" phase if the test has been
+            // configured to allow uncaught exceptions. This gives the test an
+            // opportunity to define subtests based on the exception reporting
+            // behavior.
+            if (!tests.allow_uncaught_exception) {
+                done();
+            }
+        };
+
+        addEventListener("error", function(e) {
+            var message = e.message;
+            var stack;
+            if (e.error && e.error.stack) {
+                stack = e.error.stack;
+            } else {
+                stack = e.filename + ":" + e.lineno + ":" + e.colno;
+            }
+            error_handler(e.error, message, stack);
+        }, false);
+
+        addEventListener("unhandledrejection", function(e) {
+            var message;
+            if (e.reason && e.reason.message) {
+                message = "Unhandled rejection: " + e.reason.message;
+            } else {
+                message = "Unhandled rejection";
+            }
+            var stack;
+            if (e.reason && e.reason.stack) {
+                stack = e.reason.stack;
+            }
+            error_handler(e.reason, message, stack);
+        }, false);
+    }
+
+    test_environment.on_tests_ready();
+
+    /**
+     * Stylesheet
+     */
+     var stylesheetContent = "\
+html {\
+    font-family:DejaVu Sans, Bitstream Vera Sans, Arial, Sans;\
+}\
+\
+#log .warning,\
+#log .warning a {\
+  color: black;\
+  background: yellow;\
+}\
+\
+#log .error,\
+#log .error a {\
+  color: white;\
+  background: red;\
+}\
+\
+section#summary {\
+    margin-bottom:1em;\
+}\
+\
+table#results {\
+    border-collapse:collapse;\
+    table-layout:fixed;\
+    width:100%;\
+}\
+\
+table#results > thead > tr > th:first-child,\
+table#results > tbody > tr > td:first-child {\
+    width:8em;\
+}\
+\
+table#results > thead > tr > th:last-child,\
+table#results > thead > tr > td:last-child {\
+    width:50%;\
+}\
+\
+table#results.assertions > thead > tr > th:last-child,\
+table#results.assertions > tbody > tr > td:last-child {\
+    width:35%;\
+}\
+\
+table#results > thead > > tr > th {\
+    padding:0;\
+    padding-bottom:0.5em;\
+    border-bottom:medium solid black;\
+}\
+\
+table#results > tbody > tr> td {\
+    padding:1em;\
+    padding-bottom:0.5em;\
+    border-bottom:thin solid black;\
+}\
+\
+.pass {\
+    color:green;\
+}\
+\
+.fail {\
+    color:red;\
+}\
+\
+tr.timeout {\
+    color:red;\
+}\
+\
+tr.notrun {\
+    color:blue;\
+}\
+\
+tr.optionalunsupported {\
+    color:blue;\
+}\
+\
+.ok {\
+    color:green;\
+}\
+\
+.error {\
+    color:red;\
+}\
+\
+.pass, .fail, .timeout, .notrun, .optionalunsupported .ok, .timeout, .error {\
+    font-variant:small-caps;\
+}\
+\
+table#results span {\
+    display:block;\
+}\
+\
+table#results span.expected {\
+    font-family:DejaVu Sans Mono, Bitstream Vera Sans Mono, Monospace;\
+    white-space:pre;\
+}\
+\
+table#results span.actual {\
+    font-family:DejaVu Sans Mono, Bitstream Vera Sans Mono, Monospace;\
+    white-space:pre;\
+}\
+";
+
+})(self);
+// vim: set expandtab shiftwidth=4 tabstop=4:
diff --git a/testing/web-platform/tests/resources/testharness.js.headers b/testing/web-platform/tests/resources/testharness.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/testharness.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600
diff --git a/testing/web-platform/tests/resources/testharnessreport.js b/testing/web-platform/tests/resources/testharnessreport.js
new file mode 100644
index 0000000000..e5cb40fe0e
--- /dev/null
+++ b/testing/web-platform/tests/resources/testharnessreport.js
@@ -0,0 +1,57 @@
+/* global add_completion_callback */
+/* global setup */
+
+/*
+ * This file is intended for vendors to implement code needed to integrate
+ * testharness.js tests with their own test systems.
+ *
+ * Typically test system integration will attach callbacks when each test has
+ * run, using add_result_callback(callback(test)), or when the whole test file
+ * has completed, using
+ * add_completion_callback(callback(tests, harness_status)).
+ *
+ * For more documentation about the callback functions and the
+ * parameters they are called with see testharness.js
+ */
+
+function dump_test_results(tests, status) {
+    var results_element = document.createElement("script");
+    results_element.type = "text/json";
+    results_element.id = "__testharness__results__";
+    var test_results = tests.map(function(x) {
+        return {name:x.name, status:x.status, message:x.message, stack:x.stack}
+    });
+    var data = {test:window.location.href,
+                tests:test_results,
+                status: status.status,
+                message: status.message,
+                stack: status.stack};
+    results_element.textContent = JSON.stringify(data);
+
+    // To avoid a HierarchyRequestError with XML documents, ensure that 'results_element'
+    // is inserted at a location that results in a valid document.
+    var parent = document.body
+        ? document.body                 // <body> is required in XHTML documents
+        : document.documentElement;     // fallback for optional <body> in HTML5, SVG, etc.
+
+    parent.appendChild(results_element);
+}
+
+add_completion_callback(dump_test_results);
+
+/* If the parent window has a testharness_properties object,
+ * we use this to provide the test settings. This is used by the
+ * default in-browser runner to configure the timeout and the
+ * rendering of results
+ */
+try {
+    if (window.opener && "testharness_properties" in window.opener) {
+        /* If we pass the testharness_properties object as-is here without
+         * JSON stringifying and reparsing it, IE fails & emits the message
+         * "Could not complete the operation due to error 80700019".
+         */
+        setup(JSON.parse(JSON.stringify(window.opener.testharness_properties)));
+    }
+} catch (e) {
+}
+// vim: set expandtab shiftwidth=4 tabstop=4:
diff --git a/testing/web-platform/tests/resources/testharnessreport.js.headers b/testing/web-platform/tests/resources/testharnessreport.js.headers
new file mode 100644
index 0000000000..5e8f640c66
--- /dev/null
+++ b/testing/web-platform/tests/resources/testharnessreport.js.headers
@@ -0,0 +1,2 @@
+Content-Type: text/javascript; charset=utf-8
+Cache-Control: max-age=3600