1 files changed, 49 insertions, 0 deletions
diff --git a/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-mutate-iterator-after-done.js b/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-mutate-iterator-after-done.js
new file mode 100644
index 0000000000..b9a37234a8
--- /dev/null
+++ b/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-mutate-iterator-after-done.js
@@ -0,0 +1,49 @@
+// |reftest| skip-if(!this.hasOwnProperty('AsyncIterator'))
+//
+//
+
+/*---
+esid: pending
+description: %AsyncIterator.prototype% methods ignore iterator mutation if already done.
+info: >
+  Iterator Helpers proposal 2.1.6
+features: [iterator-helpers]
+---*/
+
+class TestIterator extends AsyncIterator {
+  values = [1, 2];
+  async next() {
+    if (this.values.length == 0)
+      return {done: true};
+    return {done: false, value: this.values.shift()};
+  }
+}
+
+function check({done, value}, expectedDone, expectedValue) {
+  assertEq(done, expectedDone);
+  assertEq(Array.isArray(value) ? value[1] : value, expectedValue);
+}
+
+const methods = [
+  ['map', x => x],
+  ['filter', x => true],
+  ['take', Infinity],
+  ['drop', 0],
+  ['asIndexedPairs', undefined],
+  ['flatMap', async function*(x) { yield x; }],
+];
+
+for (const [method, arg] of methods) {
+  (async () => {
+    const iter = new TestIterator();
+    const iterHelper = iter[method](arg);
+    check(await iterHelper.next(), false, 1);
+    check(await iterHelper.next(), false, 2);
+    check(await iterHelper.next(), true, undefined);
+    iter.values.push(3);
+    check(await iterHelper.next(), true, undefined);
+  })();
+}
+
+if (typeof reportCompare == 'function')
+  reportCompare(0, 0);