1 files changed, 21 insertions, 0 deletions
diff --git a/testing/web-platform/tests/scheduler/post-task-run-order.any.js b/testing/web-platform/tests/scheduler/post-task-run-order.any.js
new file mode 100644
index 0000000000..acbe86744c
--- /dev/null
+++ b/testing/web-platform/tests/scheduler/post-task-run-order.any.js
@@ -0,0 +1,21 @@
+// META: title=Scheduler: Tasks Run in Priority Order
+// META: global=window,worker
+
+promise_test(async t => {
+  const runOrder = [];
+  const schedule = (id, priority) => scheduler.postTask(() => { runOrder.push(id); }, {priority});
+
+  // Post tasks in reverse priority order and expect they are run from highest
+  // to lowest priority.
+  const tasks = [];
+  tasks.push(schedule('B1', 'background'));
+  tasks.push(schedule('B2', 'background'));
+  tasks.push(schedule('UV1', 'user-visible'));
+  tasks.push(schedule('UV2', 'user-visible'));
+  tasks.push(schedule('UB1', 'user-blocking'));
+  tasks.push(schedule('UB2', 'user-blocking'));
+
+  await Promise.all(tasks);
+
+  assert_equals(runOrder.toString(),'UB1,UB2,UV1,UV2,B1,B2');
+}, 'Test scheduler.postTask task run in priority order');