1 files changed, 62 insertions, 0 deletions
diff --git a/testing/web-platform/tests/webidl/ecmascript-binding/class-string-interface.any.js b/testing/web-platform/tests/webidl/ecmascript-binding/class-string-interface.any.js
new file mode 100644
index 0000000000..ee792d5368
--- /dev/null
+++ b/testing/web-platform/tests/webidl/ecmascript-binding/class-string-interface.any.js
@@ -0,0 +1,62 @@
+"use strict";
+
+test(() => {
+  assert_own_property(Blob.prototype, Symbol.toStringTag);
+
+  const propDesc = Object.getOwnPropertyDescriptor(Blob.prototype, Symbol.toStringTag);
+  assert_equals(propDesc.value, "Blob", "value");
+  assert_equals(propDesc.configurable, true, "configurable");
+  assert_equals(propDesc.enumerable, false, "enumerable");
+  assert_equals(propDesc.writable, false, "writable");
+}, "@@toStringTag exists on the prototype with the appropriate descriptor");
+
+test(() => {
+  assert_not_own_property(new Blob(), Symbol.toStringTag);
+}, "@@toStringTag must not exist on the instance");
+
+test(() => {
+  assert_equals(Object.prototype.toString.call(Blob.prototype), "[object Blob]");
+}, "Object.prototype.toString applied to the prototype");
+
+test(() => {
+  assert_equals(Object.prototype.toString.call(new Blob()), "[object Blob]");
+}, "Object.prototype.toString applied to an instance");
+
+test(t => {
+  assert_own_property(Blob.prototype, Symbol.toStringTag, "Precondition for this test: @@toStringTag on the prototype");
+
+  t.add_cleanup(() => {
+    Object.defineProperty(Blob.prototype, Symbol.toStringTag, { value: "Blob" });
+  });
+
+  Object.defineProperty(Blob.prototype, Symbol.toStringTag, { value: "NotABlob" });
+  assert_equals(Object.prototype.toString.call(Blob.prototype), "[object NotABlob]", "prototype");
+  assert_equals(Object.prototype.toString.call(new Blob()), "[object NotABlob]", "instance");
+}, "Object.prototype.toString applied after modifying the prototype's @@toStringTag");
+
+test(t => {
+  const instance = new Blob();
+  assert_not_own_property(instance, Symbol.toStringTag, "Precondition for this test: no @@toStringTag on the instance");
+
+  Object.defineProperty(instance, Symbol.toStringTag, { value: "NotABlob" });
+  assert_equals(Object.prototype.toString.call(instance), "[object NotABlob]");
+}, "Object.prototype.toString applied to the instance after modifying the instance's @@toStringTag");
+
+// Chrome had a bug (https://bugs.chromium.org/p/chromium/issues/detail?id=793406) where if there
+// was no @@toStringTag in the prototype, it would fall back to a magic class string. This tests
+// that the bug is fixed.
+
+test(() => {
+  const instance = new Blob();
+  Object.setPrototypeOf(instance, null);
+
+  assert_equals(Object.prototype.toString.call(instance), "[object Object]");
+}, "Object.prototype.toString applied to a null-prototype instance");
+
+// This test must be last.
+test(() => {
+  delete Blob.prototype[Symbol.toStringTag];
+
+  assert_equals(Object.prototype.toString.call(Blob.prototype), "[object Object]", "prototype");
+  assert_equals(Object.prototype.toString.call(new Blob()), "[object Object]", "instance");
+}, "Object.prototype.toString applied after deleting @@toStringTag");