1 files changed, 51 insertions, 0 deletions
diff --git a/js/src/tests/test262/language/expressions/await/await-monkey-patched-promise.js b/js/src/tests/test262/language/expressions/await/await-monkey-patched-promise.js
new file mode 100644
index 0000000000..0ac7415bf5
--- /dev/null
+++ b/js/src/tests/test262/language/expressions/await/await-monkey-patched-promise.js
@@ -0,0 +1,51 @@
+// |reftest| async
+// Copyright 2018 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+author: Maya Lekova <mslekova@chromium.org>
+esid: await
+description: >
+  This test demonstrates that monkey-patched "then" on native promises will
+  not get called. Adapted from example by Kevin Smith:
+  https://github.com/tc39/ecma262/pull/1250#issuecomment-401082195
+flags: [async]
+features: [async-functions]
+includes: [compareArray.js]
+---*/
+
+let thenCallCount = 0;
+const value = 42;
+
+const actual = [];
+const expected = [
+  'Promise: 1',
+  'Await: ' + value,
+  'Promise: 2',
+];
+
+const patched = Promise.resolve(value);
+patched.then = function(...args) {
+  thenCallCount++;
+  Promise.prototype.then.apply(this, args);
+};
+
+async function trigger() {
+  actual.push('Await: ' + await patched);
+}
+
+function checkAssertions() {
+  assert.compareArray(actual, expected,
+    'Async/await and promises should be interleaved');
+  assert.sameValue(thenCallCount, 0,
+    'Monkey-patched "then" on native promises should not be called.')
+}
+
+trigger().then(checkAssertions).then($DONE, $DONE);
+
+new Promise(function (resolve) {
+  actual.push('Promise: 1');
+  resolve();
+}).then(function () {
+  actual.push('Promise: 2');
+});