1 files changed, 36 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/embedded-content/media-elements/track/track-element/track-selection-task-order.html b/testing/web-platform/tests/html/semantics/embedded-content/media-elements/track/track-element/track-selection-task-order.html
new file mode 100644
index 0000000000..522d067adf
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/embedded-content/media-elements/track/track-element/track-selection-task-order.html
@@ -0,0 +1,36 @@
+<!DOCTYPE html>
+<title>HTMLTrackElement Text Track Selection Task Order</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+/**
+ * This test is used to ensure that we queue 'honor user preferences for automatic
+ * text track selection' as a macro task, not a micro task. In this test, we
+ * trigger a media event before queuing a text track selection task, and check
+ * the text track's mode to know whether the text track selection runs after the
+ * task for media event.
+ */
+async_test(function(t) {
+    let video = document.createElement("video");
+    video.play();
+    video.onplay = t.step_func(startedPlay);
+
+    // When we create a text track element, it queue a task to run automatic
+    // text track selection later.
+    let track = document.createElement("track");
+    track.default = true;
+    video.appendChild(track);
+    assert_equals(track.track.mode, "disabled", "Text track's mode is disabled by default.");
+
+    function startedPlay() {
+        assert_equals(track.track.mode, "disabled", "Text track selection hasn't started yet.");
+        track.onerror = t.step_func_done(trackError);
+    }
+
+    function trackError() {
+        assert_equals(track.track.mode, "showing", "Text track selection modified track's mode.");
+        t.done();
+    }
+});
+
+</script>