1 files changed, 59 insertions, 0 deletions
diff --git a/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-interleaved.js b/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-interleaved.js
new file mode 100644
index 0000000000..98c2a2b680
--- /dev/null
+++ b/js/src/tests/non262/AsyncIterator/prototype/lazy-methods-interleaved.js
@@ -0,0 +1,59 @@
+// |reftest| skip-if(!this.hasOwnProperty('AsyncIterator'))
+
+//
+//
+/*---
+esid: pending
+description: Lazy %AsyncIterator.prototype% method calls can be interleaved.
+info: >
+  Iterator Helpers proposal 2.1.6
+features: [iterator-helpers]
+---*/
+
+class TestIterator extends AsyncIterator {
+  value = 0;
+  async next() { 
+    return {done: false, value: this.value++};
+  }
+}
+
+function unwrapResult(value) {
+  // Unwrap the asIndexedPair return values.
+  while (Array.isArray(value)) {
+    value = value[1];
+  }
+  return value;
+}
+
+function check({done, value}, expectedDone, expectedValue) {
+  assertEq(done, expectedDone);
+  assertEq(unwrapResult(value), expectedValue);
+}
+
+const methods = [
+  ['map', x => x],
+  ['filter', x => true],
+  ['take', Infinity],
+  ['drop', 0],
+  ['asIndexedPairs', undefined],
+  ['flatMap', async function*(x) { yield x; }],
+];
+
+(async () => {
+  for (const [firstMethod, firstArg] of methods) {
+    for (const [secondMethod, secondArg] of methods) {
+      const iterator = new TestIterator();
+
+      const firstHelper = iterator[firstMethod](firstArg);
+      const secondHelper = iterator[secondMethod](secondArg);
+
+      check(await firstHelper.next(), false, 0);
+      check(await secondHelper.next(), false, 1);
+      check(await firstHelper.next(), false, 2);
+      check(await secondHelper.next(), false, 3);
+    }
+  }
+})();
+
+if (typeof reportCompare == 'function')
+  reportCompare(0, 0);