From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Fri, 19 Apr 2024 02:47:55 +0200
Subject: Adding upstream version 124.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../web-platform/tests/resources/test/README.md    |  83 ++
 .../web-platform/tests/resources/test/conftest.py  | 269 ++++++
 .../web-platform/tests/resources/test/harness.html |  26 +
 .../tests/resources/test/idl-helper.js             |  24 +
 .../tests/resources/test/nested-testharness.js     |  80 ++
 .../tests/resources/test/requirements.txt          |   1 +
 .../test/tests/functional/abortsignal.html         |  49 +
 .../test/tests/functional/add_cleanup.html         |  91 ++
 .../test/tests/functional/add_cleanup_async.html   |  85 ++
 .../functional/add_cleanup_async_bad_return.html   |  50 ++
 .../functional/add_cleanup_async_rejection.html    |  94 ++
 .../add_cleanup_async_rejection_after_load.html    |  52 ++
 .../functional/add_cleanup_async_timeout.html      |  57 ++
 .../tests/functional/add_cleanup_bad_return.html   |  61 ++
 .../test/tests/functional/add_cleanup_count.html   |  39 +
 .../test/tests/functional/add_cleanup_err.html     |  45 +
 .../tests/functional/add_cleanup_err_multi.html    |  52 ++
 .../tests/functional/add_cleanup_sync_queue.html   |  55 ++
 .../test/tests/functional/api-tests-1.html         | 991 +++++++++++++++++++++
 .../test/tests/functional/api-tests-2.html         |  62 ++
 .../test/tests/functional/api-tests-3.html         |  34 +
 .../test/tests/functional/assert-array-equals.html | 162 ++++
 .../test/tests/functional/assert-throws-dom.html   |  55 ++
 .../test/tests/functional/force_timeout.html       |  60 ++
 .../test/tests/functional/generate-callback.html   | 153 ++++
 .../IdlDictionary/test_partial_interface_of.html   |  89 ++
 .../IdlInterface/test_exposed_wildcard.html        | 233 +++++
 .../IdlInterface/test_immutable_prototype.html     | 298 +++++++
 .../IdlInterface/test_interface_mixin.html         | 131 +++
 .../IdlInterface/test_partial_interface_of.html    | 187 ++++
 .../IdlInterface/test_primary_interface_of.html    | 116 +++
 .../IdlInterface/test_to_json_operation.html       | 177 ++++
 .../idlharness/IdlNamespace/test_attribute.html    | 100 +++
 .../idlharness/IdlNamespace/test_operation.html    | 242 +++++
 .../IdlNamespace/test_partial_namespace.html       | 125 +++
 .../test/tests/functional/iframe-callback.html     | 116 +++
 .../functional/iframe-consolidate-errors.html      |  50 ++
 .../tests/functional/iframe-consolidate-tests.html |  85 ++
 .../test/tests/functional/iframe-msg.html          |  84 ++
 .../test/tests/functional/log-insertion.html       |  46 +
 .../resources/test/tests/functional/no-title.html  | 146 +++
 .../resources/test/tests/functional/order.html     |  36 +
 .../test/tests/functional/promise-async.html       | 172 ++++
 .../test/tests/functional/promise-with-sync.html   |  79 ++
 .../resources/test/tests/functional/promise.html   | 219 +++++
 .../resources/test/tests/functional/queue.html     | 130 +++
 .../test/tests/functional/setup-function-worker.js |  14 +
 .../tests/functional/setup-worker-service.html     |  86 ++
 .../tests/functional/single-page-test-fail.html    |  28 +
 .../functional/single-page-test-no-assertions.html |  25 +
 .../tests/functional/single-page-test-no-body.html |  26 +
 .../tests/functional/single-page-test-pass.html    |  28 +
 .../resources/test/tests/functional/step_wait.html |  79 ++
 .../test/tests/functional/step_wait_func.html      |  49 +
 .../functional/task-scheduling-promise-test.html   | 241 +++++
 .../tests/functional/task-scheduling-test.html     | 141 +++
 .../functional/uncaught-exception-handle.html      |  33 +
 .../functional/uncaught-exception-ignore.html      |  35 +
 .../worker-dedicated-uncaught-allow.html           |  45 +
 .../worker-dedicated-uncaught-single.html          |  56 ++
 .../tests/functional/worker-dedicated.sub.html     |  88 ++
 .../test/tests/functional/worker-error.js          |   8 +
 .../test/tests/functional/worker-service.html      | 115 +++
 .../test/tests/functional/worker-shared.html       |  73 ++
 .../test/tests/functional/worker-uncaught-allow.js |  19 +
 .../tests/functional/worker-uncaught-single.js     |   8 +
 .../resources/test/tests/functional/worker.js      |  34 +
 .../test/tests/unit/IdlArray/is_json_type.html     | 192 ++++
 .../get_reverse_inheritance_stack.html             |  47 +
 .../IdlDictionary/test_partial_dictionary.html     |  39 +
 .../test/tests/unit/IdlInterface/constructors.html |  26 +
 .../IdlInterface/default_to_json_operation.html    | 114 +++
 .../IdlInterface/do_member_unscopable_asserts.html |  56 ++
 .../unit/IdlInterface/get_interface_object.html    |  22 +
 .../IdlInterface/get_interface_object_owner.html   |  21 +
 .../unit/IdlInterface/get_legacy_namespace.html    |  20 +
 .../unit/IdlInterface/get_qualified_name.html      |  20 +
 .../get_reverse_inheritance_stack.html             |  49 +
 .../has_default_to_json_regular_operation.html     |  47 +
 .../has_to_json_regular_operation.html             |  31 +
 .../IdlInterface/should_have_interface_object.html |  30 +
 .../test_primary_interface_of_undefined.html       |  29 +
 .../is_to_json_regular_operation.html              |  42 +
 .../tests/unit/IdlInterfaceMember/toString.html    |  36 +
 .../test/tests/unit/assert_implements.html         |  43 +
 .../tests/unit/assert_implements_optional.html     |  43 +
 .../test/tests/unit/assert_object_equals.html      | 152 ++++
 .../tests/unit/async-test-return-restrictions.html | 135 +++
 .../tests/resources/test/tests/unit/basic.html     |  48 +
 .../tests/unit/exceptional-cases-timeouts.html     | 120 +++
 .../test/tests/unit/exceptional-cases.html         | 392 ++++++++
 .../resources/test/tests/unit/format-value.html    | 123 +++
 .../tests/resources/test/tests/unit/helpers.js     |  21 +
 .../tests/resources/test/tests/unit/late-test.html |  56 ++
 .../test/tests/unit/promise_setup-timeout.html     |  28 +
 .../resources/test/tests/unit/promise_setup.html   | 333 +++++++
 .../resources/test/tests/unit/single_test.html     |  94 ++
 .../test/tests/unit/test-return-restrictions.html  | 156 ++++
 .../test/tests/unit/throwing-assertions.html       | 268 ++++++
 .../test/tests/unit/unpaired-surrogates.html       | 143 +++
 testing/web-platform/tests/resources/test/tox.ini  |  13 +
 .../web-platform/tests/resources/test/wptserver.py |  58 ++
 102 files changed, 9869 insertions(+)
 create mode 100644 testing/web-platform/tests/resources/test/README.md
 create mode 100644 testing/web-platform/tests/resources/test/conftest.py
 create mode 100644 testing/web-platform/tests/resources/test/harness.html
 create mode 100644 testing/web-platform/tests/resources/test/idl-helper.js
 create mode 100644 testing/web-platform/tests/resources/test/nested-testharness.js
 create mode 100644 testing/web-platform/tests/resources/test/requirements.txt
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/abortsignal.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_bad_return.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_rejection_after_load.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_async_timeout.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_bad_return.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_count.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_err_multi.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/add_cleanup_sync_queue.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/api-tests-1.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/api-tests-2.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/api-tests-3.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/assert-array-equals.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/assert-throws-dom.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/force_timeout.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/generate-callback.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlDictionary/test_partial_interface_of.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_exposed_wildcard.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_immutable_prototype.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_interface_mixin.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_partial_interface_of.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_primary_interface_of.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_to_json_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_attribute.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlNamespace/test_partial_namespace.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/iframe-callback.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-errors.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/iframe-consolidate-tests.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/iframe-msg.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/log-insertion.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/no-title.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/order.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/promise-async.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/promise-with-sync.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/promise.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/queue.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/setup-function-worker.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/setup-worker-service.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/single-page-test-fail.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-assertions.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/single-page-test-no-body.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/single-page-test-pass.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/step_wait.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/step_wait_func.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/task-scheduling-promise-test.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/task-scheduling-test.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-handle.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/uncaught-exception-ignore.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-allow.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-dedicated-uncaught-single.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-dedicated.sub.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-error.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-service.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-shared.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-allow.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker-uncaught-single.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/functional/worker.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlArray/is_json_type.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/get_reverse_inheritance_stack.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlDictionary/test_partial_dictionary.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/constructors.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/default_to_json_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/do_member_unscopable_asserts.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_interface_object_owner.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_legacy_namespace.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_qualified_name.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/get_reverse_inheritance_stack.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_default_to_json_regular_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/has_to_json_regular_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/should_have_interface_object.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterface/test_primary_interface_of_undefined.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/is_to_json_regular_operation.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/IdlInterfaceMember/toString.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/assert_implements.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/assert_implements_optional.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/assert_object_equals.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/async-test-return-restrictions.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/basic.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/exceptional-cases-timeouts.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/exceptional-cases.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/format-value.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/helpers.js
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/late-test.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/promise_setup-timeout.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/promise_setup.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/single_test.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/test-return-restrictions.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/throwing-assertions.html
 create mode 100644 testing/web-platform/tests/resources/test/tests/unit/unpaired-surrogates.html
 create mode 100644 testing/web-platform/tests/resources/test/tox.ini
 create mode 100644 testing/web-platform/tests/resources/test/wptserver.py

(limited to 'testing/web-platform/tests/resources/test')

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..f635768c69
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlDictionary/test_partial_interface_of.html
@@ -0,0 +1,89 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <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..7dd9e676af
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/idlharness/IdlInterface/test_partial_interface_of.html
@@ -0,0 +1,187 @@
+<!DOCTYPE HTML>
+<html>
+
+<head>
+  <meta charset="utf-8">
+  <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..8235d9d48a
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/functional/step_wait.html
@@ -0,0 +1,79 @@
+<!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");
+
+promise_test(async t => {
+  function wait(ms) {
+    return new Promise(resolve => step_timeout(resolve, ms));
+  }
+  let x = 1;
+  step_timeout(() => {
+    ++x;
+  }, 100);
+
+  await t.step_wait(async () => {
+    await wait(1);
+    return x === 2;
+  });
+  assert_equals(x, 2);
+}, "async step_wait()");
+</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"
+    },
+    {
+      "name": "async step_wait()",
+      "message": null,
+      "properties": {},
+      "status_string": "PASS"
+    }
+  ],
+  "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..c9f8ec61fe
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tests/unit/late-test.html
@@ -0,0 +1,56 @@
+<!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 included in the dataset.</p>
+
+<p>Although these "late tests" are likely an indication of a mistake in test
+design, they are also recorded. Previously, "late tests" were ignored.
+This test changed to assert "late tests" were no longer ignored after
+https://github.com/web-platform-tests/wpt/pull/38806 was introduced.</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() {}, 'test registered in onload handler');",
+        "};",
+        "</" + "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, 2);
+                assert_equals(tests[0].name, "acceptable test");
+                assert_equals(tests[1].name, "test registered in onload handler");
+                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..12013a1a70
--- /dev/null
+++ b/testing/web-platform/tests/resources/test/tox.ini
@@ -0,0 +1,13 @@
+[tox]
+envlist = py37,py38,py39,py310,py311
+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)
-- 
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