1 files changed, 18 insertions, 0 deletions
diff --git a/testing/web-platform/tests/compute-pressure/observe_return_type.https.any.js b/testing/web-platform/tests/compute-pressure/observe_return_type.https.any.js
new file mode 100644
index 0000000000..b24878ab39
--- /dev/null
+++ b/testing/web-platform/tests/compute-pressure/observe_return_type.https.any.js
@@ -0,0 +1,18 @@
+// META: script=/resources/test-only-api.js
+// META: script=resources/pressure-helpers.js
+// META: global=window,dedicatedworker,sharedworker
+
+'use strict';
+
+// Regression test for https://issues.chromium.org/issues/333957909
+// Make sure that observe() always returns a Promise.
+pressure_test(async (t, mockPressureService) => {
+  const observer = new PressureObserver(() => {});
+  t.add_cleanup(() => observer.disconnect());
+
+  for (let i = 0; i < 2; i++) {
+    const promise = observer.observe('cpu');
+    assert_class_string(promise, 'Promise');
+    await promise;
+  }
+}, 'PressureObserver.observe() is idempotent');