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Test Info:

<title>Check element's ready state while suspending video decoding</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<script src="manifest.js"></script>
<script src="background_video.js"></script>
<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
<script type="application/javascript">
* This test is used to ensure that the media element's ready state won't be
* incorrectly changed to `HAVE_METADATA` or lower when seeking happens on a
* null decoder that is caused by suspending video decoding.
add_task(async function setupTestingPref() {
await SpecialPowers.pushPrefEnv({
set: [
["", true],
["media.suspend-background-video.enabled", true],
["media.suspend-background-video.delay-ms", 0],
add_task(async function testReadyStateWhenSuspendingVideoDecoding() {
const video = await createPlayingVideo();
await suspendVideoDecoding(video);
await seekVideo(video);
async function createPlayingVideo() {
let video = document.createElement("video");
video.src = "gizmo.mp4";
video.controls = true;
video.loop = true;
ok(await>true, _=>false), "video started playing");
return video;
function assertVideoReadyStateIsSufficientForPlaying(video) {
ok(video.readyState > HTMLMediaElement.HAVE_METADATA,
`Ready state ${video.readyState} is suffient for playing`);
async function suspendVideoDecoding(video) {
info(`suspended video decoding`);
// Because the suspend event we received can only indicate MDSM finishes the
// setup of suspending decoding, but the actual setting the null decoder
// happens on MediaFormatReader where we are not able to observe the behavior
// via event. Instread of implementing something in MFR to propagate the event
// or changing the timing of current suspend event, which might increase the
// maintenance effect, Here choose to use a simple workaround to wait for a
// short while to ensure the decoding has been switched to the null decoder.
// eslint-disable-next-line mozilla/no-arbitrary-setTimeout
await new Promise(resolve => setTimeout(resolve, 2000));
async function seekVideo(video) {
video.currentTime = 0;
ok(await new Promise(r => video.onseeked = r).then(_=>true, _=>false),
`seeking completed`);