1 files changed, 53 insertions, 0 deletions
diff --git a/testing/web-platform/tests/streams/transform-streams/patched-global.any.js b/testing/web-platform/tests/streams/transform-streams/patched-global.any.js
new file mode 100644
index 0000000000..2d04e3b948
--- /dev/null
+++ b/testing/web-platform/tests/streams/transform-streams/patched-global.any.js
@@ -0,0 +1,53 @@
+// META: global=window,worker
+'use strict';
+
+// Tests which patch the global environment are kept separate to avoid
+// interfering with other tests.
+
+test(t => {
+  // eslint-disable-next-line no-extend-native, accessor-pairs
+  Object.defineProperty(Object.prototype, 'highWaterMark', {
+    set() { throw new Error('highWaterMark setter called'); },
+    configurable: true
+  });
+
+  // eslint-disable-next-line no-extend-native, accessor-pairs
+  Object.defineProperty(Object.prototype, 'size', {
+    set() { throw new Error('size setter called'); },
+    configurable: true
+  });
+
+  t.add_cleanup(() => {
+    delete Object.prototype.highWaterMark;
+    delete Object.prototype.size;
+  });
+
+  assert_not_equals(new TransformStream(), null, 'constructor should work');
+}, 'TransformStream constructor should not call setters for highWaterMark or size');
+
+test(t => {
+  const oldReadableStream = ReadableStream;
+  const oldWritableStream = WritableStream;
+  const getReader = ReadableStream.prototype.getReader;
+  const getWriter = WritableStream.prototype.getWriter;
+
+  // Replace ReadableStream and WritableStream with broken versions.
+  ReadableStream = function () {
+    throw new Error('Called the global ReadableStream constructor');
+  };
+  WritableStream = function () {
+    throw new Error('Called the global WritableStream constructor');
+  };
+  t.add_cleanup(() => {
+    ReadableStream = oldReadableStream;
+    WritableStream = oldWritableStream;
+  });
+
+  const ts = new TransformStream();
+
+  // Just to be sure, ensure the readable and writable pass brand checks.
+  assert_not_equals(getReader.call(ts.readable), undefined,
+                    'getReader should work when called on ts.readable');
+  assert_not_equals(getWriter.call(ts.writable), undefined,
+                    'getWriter should work when called on ts.writable');
+}, 'TransformStream should use the original value of ReadableStream and WritableStream');