1 files changed, 57 insertions, 0 deletions
diff --git a/testing/web-platform/tests/common/stringifiers.js b/testing/web-platform/tests/common/stringifiers.js
new file mode 100644
index 0000000000..8dadac1d49
--- /dev/null
+++ b/testing/web-platform/tests/common/stringifiers.js
@@ -0,0 +1,57 @@
+/**
+ * Runs tests for <https://webidl.spec.whatwg.org/#es-stringifier>.
+ * @param {Object} aObject - object to test
+ * @param {string} aAttribute - IDL attribute name that is annotated with `stringifier`
+ * @param {boolean} aIsUnforgeable - whether the IDL attribute is `[LegacyUnforgeable]`
+ */
+function test_stringifier_attribute(aObject, aAttribute, aIsUnforgeable) {
+  // Step 1.
+  test(function() {
+    [null, undefined].forEach(function(v) {
+      assert_throws_js(TypeError, function() {
+        aObject.toString.call(v);
+      });
+    });
+  });
+
+  // TODO Step 2: security check.
+
+  // Step 3.
+  test(function() {
+    assert_false("Window" in window && aObject instanceof window.Window);
+    [{}, window].forEach(function(v) {
+      assert_throws_js(TypeError, function() {
+        aObject.toString.call(v)
+      });
+    });
+  });
+
+  // Step 4-6.
+  var expected_value;
+  test(function() {
+    expected_value = aObject[aAttribute];
+    assert_equals(aObject[aAttribute], expected_value,
+                  "The attribute " + aAttribute + " should be pure.");
+  });
+
+  var test_error = { name: "test" };
+  test(function() {
+    if (!aIsUnforgeable) {
+      Object.defineProperty(aObject, aAttribute, {
+        configurable: true,
+        get: function() { throw test_error; }
+      });
+    }
+    assert_equals(aObject.toString(), expected_value);
+  });
+
+  test(function() {
+    if (!aIsUnforgeable) {
+      Object.defineProperty(aObject, aAttribute, {
+        configurable: true,
+        value: { toString: function() { throw test_error; } }
+      });
+    }
+    assert_equals(aObject.toString(), expected_value);
+  });
+}