test_accumulated_play_time.html

mozilla-central/dom/media/test/chrome/test_accumulated_play_time.html (file symbol)

Enable keyboard shortcuts

Source code

File a bug in Core :: Audio/Video: Playback

Revision control

Copy as Markdown

Other Tools

Test Info:

Manifest: dom/media/test/chrome/chrome.toml

<!DOCTYPE HTML>

<html>

<head>

<title>Test Video Play Time Related Permanent Telemetry Probes</title>

<script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>

<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>

<script type="application/javascript">

/**

 * This test is used to ensure that we accumulate time for video playback

 * correctly, and the results would be used in Telemetry probes.

 * Currently this test covers following probes

 * - VIDEO_PLAY_TIME_MS

 * - VIDEO_HDR_PLAY_TIME_MS

 * - VIDEO_HIDDEN_PLAY_TIME_MS

 * - VIDEO_HIDDEN_PLAY_TIME_PERCENTAGE

 * - VIDEO_VISIBLE_PLAY_TIME_MS

 * - MEDIA_PLAY_TIME_MS

 * - MUTED_PLAY_TIME_PERCENT

 * - AUDIBLE_PLAY_TIME_PERCENT

*/

const videoHistNames = [

  "VIDEO_PLAY_TIME_MS",

  "VIDEO_HIDDEN_PLAY_TIME_MS"

];

const videoHDRHistNames = [

  "VIDEO_HDR_PLAY_TIME_MS"

];

const videoKeyedHistNames = [

  "VIDEO_HIDDEN_PLAY_TIME_PERCENTAGE",

  "VIDEO_VISIBLE_PLAY_TIME_MS"

];

const audioKeyedHistNames = [

  "MUTED_PLAY_TIME_PERCENT",

  "AUDIBLE_PLAY_TIME_PERCENT"

];

add_task(async function setTestPref() {

  await SpecialPowers.pushPrefEnv({

    set: [["media.testing-only-events", true],

          ["media.test.video-suspend", true],

          ["media.suspend-background-video.enabled", true],

          ["media.suspend-background-video.delay-ms", 0],

          ["dom.media.silence_duration_for_audibility", 0.1]

    ]});

});

add_task(async function testTotalPlayTime() {

  const video = document.createElement('video');

  video.src = "gizmo.mp4";

  document.body.appendChild(video);

  info(`all accumulated time should be zero`);

  const videoChrome = SpecialPowers.wrap(video);

  await new Promise(r => video.onloadeddata = r);

  assertValueEqualTo(videoChrome, "totalVideoPlayTime", 0);

  assertValueEqualTo(videoChrome, "invisiblePlayTime", 0);

  info(`start accumulating play time after media starts`);

  video.autoplay = true;

  await Promise.all([

    once(video, "playing"),

    once(video, "moztotalplaytimestarted"),

]);

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

  info(`should not accumulate time for paused video`);

  video.pause();

  await once(video, "moztotalplaytimepaused");

  assertValueKeptUnchanged(videoChrome, "totalVideoPlayTime");

  assertValueEqualTo(videoChrome, "totalVideoPlayTime", 0);

  info(`should start accumulating time again`);

  let rv = await Promise.all([

    onceWithTrueReturn(video, "moztotalplaytimestarted"),

    video.play().then(_ => true, _ => false),

]);

  ok(returnTrueWhenAllValuesAreTrue(rv), "video started again");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  await cleanUpMediaAndCheckTelemetry(video);

});

// The testHDRPlayTime task will only pass on platforms that accurately report

// color depth in their VideoInfo structures. Presently, that is only true for

// macOS.

const {AppConstants} = ChromeUtils.importESModule(

  "resource://gre/modules/AppConstants.sys.mjs"

);

const reportsColorDepthFromVideoData = (AppConstants.platform == "macosx");

if (reportsColorDepthFromVideoData) {

  add_task(async function testHDRPlayTime() {

    // This task is different from the others because the HTMLMediaElement does

    // not expose a chrome property for video hdr play time. But we do capture

    // telemety for VIDEO_HDR_PLAY_TIME_MS. To ensure that this telemetry is

    // generated, this task follows the same structure as the other tasks, but

    // doesn't actually check the properties of the video player, other than to

    // confirm that video has played for at least some time.

    const video = document.createElement('video');

    video.src = "TestPatternHDR.mp4"; // This is an HDR video with no audio.

    document.body.appendChild(video);

    info(`load the HDR video`);

    const videoChrome = SpecialPowers.wrap(video);

    await new Promise(r => video.onloadeddata = r);

    info(`start accumulating play time after media starts`);

    video.autoplay = true;

    await Promise.all([

      once(video, "playing"),

      once(video, "moztotalplaytimestarted"),

]);

    // Check that we have at least some video play time, because the

    // HDR play time telemetry is emitted by the same process.

    await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

    await cleanUpMediaAndCheckTelemetry(video, {hasVideo: true, hasAudio: false, hasVideoHDR: true});

});

add_task(async function testVisiblePlayTime() {

  const video = document.createElement('video');

  video.src = "gizmo.mp4";

  document.body.appendChild(video);

  info(`all accumulated time should be zero`);

  const videoChrome = SpecialPowers.wrap(video);

  await new Promise(r => video.onloadeddata = r);

  assertValueEqualTo(videoChrome, "totalVideoPlayTime", 0);

  assertValueEqualTo(videoChrome, "visiblePlayTime", 0);

  assertValueEqualTo(videoChrome, "invisiblePlayTime", 0);

  info(`start accumulating play time after media starts`);

  video.autoplay = true;

  await Promise.all([

    once(video, "playing"),

    once(video, "moztotalplaytimestarted"),

]);

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  await assertValueConstantlyIncreases(videoChrome, "visiblePlayTime");

  assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

  info(`make video invisible`);

  video.style.display = "none";

  await once(video, "mozinvisibleplaytimestarted");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  await assertValueConstantlyIncreases(videoChrome, "invisiblePlayTime");

  assertValueKeptUnchanged(videoChrome, "visiblePlayTime");

  await cleanUpMediaAndCheckTelemetry(video);

});

add_task(async function testAudibleAudioPlayTime() {

  const audio = document.createElement('audio');

  audio.src = "tone2s-silence4s-tone2s.opus";

  audio.controls = true;

  audio.loop = true;

  document.body.appendChild(audio);

  info(`all accumulated time should be zero`);

  const audioChrome = SpecialPowers.wrap(audio);

  await new Promise(r => audio.onloadeddata = r);

  assertValueEqualTo(audioChrome, "totalVideoPlayTime", 0);

  assertValueEqualTo(audioChrome, "totalAudioPlayTime", 0);

  assertValueEqualTo(audioChrome, "mutedPlayTime", 0);

  assertValueEqualTo(audioChrome, "audiblePlayTime", 0);

  info(`start accumulating play time after media starts`);

  await Promise.all([

    audio.play(),

    once(audio, "moztotalplaytimestarted"),

]);

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  info(`audio becomes inaudible for 4s`);

  await once(audio, "mozinaudibleaudioplaytimestarted");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  assertValueKeptUnchanged(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  info(`audio becomes audible after 4s`);

  await once(audio, "mozinaudibleaudioplaytimepaused");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  await cleanUpMediaAndCheckTelemetry(audio, {hasVideo: false});

});

add_task(async function testHiddenPlayTime() {

  const invisibleReasons = ["notInTree", "notInConnectedTree", "invisibleInDisplay"];

  for (let reason of invisibleReasons) {

    const video = document.createElement('video');

    video.src = "gizmo.mp4";

    video.loop = true;

    info(`invisible video due to '${reason}'`);

    if (reason == "notInConnectedTree") {

      let disconnected = document.createElement("div")

      disconnected.appendChild(video);

    } else if (reason == "invisibleInDisplay") {

      document.body.appendChild(video);

      video.style.display = "none";

    } else if (reason == "notInTree") {

      // video is already created in the `notInTree` situation.

    } else {

      ok(false, "undefined reason");

    info(`start invisible video should start accumulating timers`);

    const videoChrome = SpecialPowers.wrap(video);

    let rv = await Promise.all([

      onceWithTrueReturn(video, "mozinvisibleplaytimestarted"),

      video.play().then(_ => true, _ => false),

]);

    ok(returnTrueWhenAllValuesAreTrue(rv), "video started playing");

    await assertValueConstantlyIncreases(videoChrome, "invisiblePlayTime");

    info(`should not accumulate time for paused video`);

    video.pause();

    await once(video, "mozinvisibleplaytimepaused");

    assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

    info(`should start accumulating time again`);

    rv = await Promise.all([

      onceWithTrueReturn(video, "mozinvisibleplaytimestarted"),

      video.play().then(_ => true, _ => false),

]);

    ok(returnTrueWhenAllValuesAreTrue(rv), "video started again");

    await assertValueConstantlyIncreases(videoChrome, "invisiblePlayTime");

    info(`make video visible should stop accumulating invisible related time`);

    if (reason == "notInTree" || reason == "notInConnectedTree") {

      document.body.appendChild(video);

    } else if (reason == "invisibleInDisplay") {

      video.style.display = "block";

    } else {

      ok(false, "undefined reason");

    await once(video, "mozinvisibleplaytimepaused");

    assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

    await cleanUpMediaAndCheckTelemetry(video);

});

add_task(async function testAudioProbesWithoutAudio() {

  const video = document.createElement('video');

  video.src = "gizmo-noaudio.mp4";

  video.loop = true;

  document.body.appendChild(video);

  info(`all accumulated time should be zero`);

  const videoChrome = SpecialPowers.wrap(video);

  await new Promise(r => video.onloadeddata = r);

  assertValueEqualTo(videoChrome, "totalVideoPlayTime", 0);

  assertValueEqualTo(videoChrome, "totalAudioPlayTime", 0);

  assertValueEqualTo(videoChrome, "mutedPlayTime", 0);

  assertValueEqualTo(videoChrome, "audiblePlayTime", 0);

  info(`start accumulating play time after media starts`);

  await Promise.all([

    video.play(),

    once(video, "moztotalplaytimestarted"),

]);

  async function checkInvariants() {

    await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

    assertValueKeptUnchanged(videoChrome, "audiblePlayTime");

    assertValueKeptUnchanged(videoChrome, "mutedPlayTime");

    assertValueKeptUnchanged(videoChrome, "totalAudioPlayTime");

  checkInvariants();

  video.muted = true;

  checkInvariants();

  video.currentTime = 0.0;

  await once(video, "seeked");

  checkInvariants();

  video.muted = false;

  checkInvariants();

  video.volume = 0.0;

  checkInvariants();

  video.volume = 1.0;

  checkInvariants();

  video.muted = true;

  checkInvariants();

  video.currentTime = 0.0;

  checkInvariants();

  await cleanUpMediaAndCheckTelemetry(video, {hasAudio: false});

});

add_task(async function testMutedAudioPlayTime() {

  const audio = document.createElement('audio');

  audio.src = "gizmo.mp4";

  audio.controls = true;

  audio.loop = true;

  document.body.appendChild(audio);

  info(`all accumulated time should be zero`);

  const audioChrome = SpecialPowers.wrap(audio);

  await new Promise(r => audio.onloadeddata = r);

  assertValueEqualTo(audioChrome, "totalVideoPlayTime", 0);

  assertValueEqualTo(audioChrome, "totalAudioPlayTime", 0);

  assertValueEqualTo(audioChrome, "mutedPlayTime", 0);

  assertValueEqualTo(audioChrome, "audiblePlayTime", 0);

  info(`start accumulating play time after media starts`);

  await Promise.all([

    audio.play(),

    once(audio, "moztotalplaytimestarted"),

]);

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.muted = true;

  await once(audio, "mozmutedaudioplaytimestarted");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "mutedPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.currentTime = 0.0;

  await once(audio, "seeked");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "mutedPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.muted = false;

  await once(audio, "mozmutedeaudioplaytimepaused");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.volume = 0.0;

  await once(audio, "mozmutedaudioplaytimestarted");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "mutedPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.volume = 1.0;

  await once(audio, "mozmutedeaudioplaytimepaused");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "mutedPlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.muted = true;

  await once(audio, "mozmutedaudioplaytimestarted");

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "mutedPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  audio.currentTime = 0.0;

  await assertValueConstantlyIncreases(audioChrome, "totalAudioPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "mutedPlayTime");

  await assertValueConstantlyIncreases(audioChrome, "audiblePlayTime");

  assertValueKeptUnchanged(audioChrome, "totalVideoPlayTime");

  // The media has a video track, but it's being played back in an

  // HTMLAudioElement, without video frame location.

  await cleanUpMediaAndCheckTelemetry(audio, {hasVideo: false});

});

// Note that video suspended time is not always align with the invisible play

// time even if `media.suspend-background-video.delay-ms` is `0`, because not all

// invisible videos would be suspended under current strategy.

add_task(async function testDecodeSuspendedTime() {

  const video = document.createElement('video');

  video.src = "gizmo.mp4";

  video.loop = true;

  document.body.appendChild(video);

  info(`start video should start accumulating timers`);

  const videoChrome = SpecialPowers.wrap(video);

  let rv = await Promise.all([

    onceWithTrueReturn(video, "moztotalplaytimestarted"),

    video.play().then(_ => true, _ => false),

]);

  ok(returnTrueWhenAllValuesAreTrue(rv), "video started playing");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

  info(`make it invisible and force to suspend decoding`);

  video.setVisible(false);

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  await assertValueConstantlyIncreases(videoChrome, "invisiblePlayTime");

  info(`make it visible and resume decoding`);

  video.setVisible(true);

  await once(video, "mozinvisibleplaytimepaused");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

  await cleanUpMediaAndCheckTelemetry(video);

});

add_task(async function reuseSameElementForPlayback() {

  const video = document.createElement('video');

  video.src = "gizmo.mp4";

  document.body.appendChild(video);

  info(`start accumulating play time after media starts`);

  const videoChrome = SpecialPowers.wrap(video);

  let rv = await Promise.all([

    onceWithTrueReturn(video, "moztotalplaytimestarted"),

    video.play().then(_ => true, _ => false),

]);

  ok(returnTrueWhenAllValuesAreTrue(rv), "video started again");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  info(`reset its src and all accumulated value should be reset after then`);

  // After setting its src to nothing, that would trigger a failed load and set

  // the error. If the following step tries to set the new resource and `play()`

  // , then they should be done after receving the `error` from that failed load

  // first.

  await Promise.all([

    once(video, "error"),

    cleanUpMediaAndCheckTelemetry(video),

]);

  // video doesn't have a decoder, so the return value would be -1 (error).

  assertValueEqualTo(videoChrome, "totalVideoPlayTime", -1);

  assertValueEqualTo(videoChrome, "invisiblePlayTime", -1);

  info(`resue same element, make it visible and start playback again`);

  video.src = "gizmo.mp4";

  rv = await Promise.all([

    onceWithTrueReturn(video, "moztotalplaytimestarted"),

    video.play().then(_ => true, _ => false),

]);

  ok(returnTrueWhenAllValuesAreTrue(rv), "video started");

  await assertValueConstantlyIncreases(videoChrome, "totalVideoPlayTime");

  await cleanUpMediaAndCheckTelemetry(video);

});

add_task(async function testNoReportedTelemetryResult() {

  info(`No result for empty video`);

  const video = document.createElement('video');

  assertAllProbeRelatedAttributesKeptUnchanged(video);

  await assertNoReportedTelemetryResult(video);

  info(`No result for video which hasn't started playing`);

  video.src = "gizmo.mp4";

  document.body.appendChild(video);

  ok(await once(video, "loadeddata").then(_ => true), "video loaded data");

  assertAllProbeRelatedAttributesKeptUnchanged(video);

  await assertNoReportedTelemetryResult(video);

  info(`No result for video with error`);

  video.src = "filedoesnotexist.mp4";

  ok(await video.play().then(_ => false, _ => true), "video failed to play");

  ok(video.error != undefined, "video got error");

  assertAllProbeRelatedAttributesKeptUnchanged(video);

  await assertNoReportedTelemetryResult(video);

});

/**

 * Following are helper functions

*/

async function cleanUpMediaAndCheckTelemetry(media, { reportExpected = true, hasVideo = true, hasAudio = true, hasVideoHDR = false } = {}) {

  media.src = "";

  await checkReportedTelemetry(media, reportExpected, hasVideo, hasAudio, hasVideoHDR);

async function assertNoReportedTelemetryResult(media) {

  await checkReportedTelemetry(media, false, true, true);

async function checkReportedTelemetry(media, reportExpected, hasVideo, hasAudio, hasVideoHDR) {

  const reportResultPromise = once(media, "mozreportedtelemetry");

  info(`check telemetry result, reportExpected=${reportExpected}`);

  if (reportExpected) {

    await reportResultPromise;

  for (const name of videoHistNames) {

    try {

      const hist = SpecialPowers.Services.telemetry.getHistogramById(name);

/**

       * Histogram's snapshot looks like that

* {

       *    "bucket_count": X,

       *    "histogram_type": Y,

       *    "sum": Z,

       *    "range": [min, max],

       *    "values": { "value1" : "num1", "value2" : "num2", ...}

* }

*/

      const entriesNums = Object.entries(hist.snapshot().values).length;

      if (reportExpected && hasVideo) {

        ok(entriesNums > 0, `Reported result for ${name}`);

      } else {

        ok(entriesNums == 0, `Reported nothing for ${name}`);

      hist.clear();

    } catch (e) {

      ok(false , `histogram '${name}' doesn't exist`);

  // videoHDRHistNames are checked for total time, not for number of samples.

  for (const name of videoHDRHistNames) {

    try {

      const hist = SpecialPowers.Services.telemetry.getHistogramById(name);

      const totalTimeMS = hist.snapshot().sum;

      if (reportExpected && hasVideoHDR) {

        ok(totalTimeMS > 0, `Reported some time for ${name}`);

      } else {

        ok(totalTimeMS == 0, `Reported no time for ${name}`);

      hist.clear();

    } catch (e) {

      ok(false , `histogram '${name}' doesn't exist`);

  for (const name of videoKeyedHistNames) {

    try {

      const hist = SpecialPowers.Services.telemetry.getKeyedHistogramById(name);

/**

       * Keyed Histogram's snapshot looks like that

* {

       *    "Key1" : {

       *      "bucket_count": X,

       *      "histogram_type": Y,

       *      "sum": Z,

       *      "range": [min, max],

       *      "values": { "value1" : "num1", "value2" : "num2", ...}

       *    },

       *    "Key2" : {...},

* }

*/

      const items = Object.entries(hist.snapshot());

      if (items.length) {

        for (const [key, value] of items) {

          const entriesNums = Object.entries(value.values).length;

          ok(reportExpected && entriesNums > 0, `Reported ${key} for ${name}`);

      } else if (reportExpected) {

        ok(!hasVideo, `No video telemetry reported but no video track in the media`);

      } else {

        ok(true, `No video telemetry expected, none reported`);

      // Avoid to pollute next test task.

      hist.clear();

    } catch (e) {

      ok(false , `keyed histogram '${name}' doesn't exist`);

  // In any case, the combined probe MEDIA_PLAY_TIME_MS should be reported, if

  // expected

    const hist =

      SpecialPowers.Services.telemetry.getKeyedHistogramById("MEDIA_PLAY_TIME_MS");

    const items = Object.entries(hist.snapshot());

    if (items.length) {

      for (const item of items) {

        ok(item[0].includes("V") != -1 || !hasVideo, "Video time is reported if video was present");

      hist.clear();

    } else {

      ok(!reportExpected, "MEDIA_PLAY_TIME_MS should always be reported if a report is expected");

  for (const name of audioKeyedHistNames) {

    try {

      const hist = SpecialPowers.Services.telemetry.getKeyedHistogramById(name);

      const items = Object.entries(hist.snapshot());

      if (items.length) {

        for (const [key, value] of items) {

          const entriesNums = Object.entries(value.values).length;

          ok(reportExpected && entriesNums > 0, `Reported ${key} for ${name}`);

      } else {

        ok(!reportExpected || !hasAudio, `No audio telemetry expected, none reported`);

      // Avoid to pollute next test task.

      hist.clear();

    } catch (e) {

      ok(false , `keyed histogram '${name}' doesn't exist`);

function once(target, name) {

  return new Promise(r => target.addEventListener(name, r, { once: true }));

function onceWithTrueReturn(target, name) {

  return once(target, name).then(_ => true);

function returnTrueWhenAllValuesAreTrue(arr) {

  for (let val of arr) {

    if (!val) {

      return false;

  return true;

// Block the main thread for a number of milliseconds

function blockMainThread(durationMS) {

  const start = Date.now();

  while (Date.now() - start < durationMS) { /* spin */ }

// Allows comparing two values from the system clocks that are not gathered

// atomically. Allow up to 1ms of fuzzing when lhs and rhs are seconds.

function timeFuzzyEquals(lhs, rhs, str) {

  ok(Math.abs(lhs - rhs) < 1e-3, str);

function assertAttributeDefined(mediaChrome, checkType) {

  ok(mediaChrome[checkType] != undefined, `${checkType} exists`);

function assertValueEqualTo(mediaChrome, checkType, expectedValue) {

  assertAttributeDefined(mediaChrome, checkType);

  is(mediaChrome[checkType], expectedValue, `${checkType} equals to ${expectedValue}`);

async function assertValueConstantlyIncreases(mediaChrome, checkType) {

  assertAttributeDefined(mediaChrome, checkType);

  const valueSnapshot = mediaChrome[checkType];

  // 30ms is long enough to have a low-resolution system clock tick, but short

  // enough to not slow the test down.

  blockMainThread(30);

  const current = mediaChrome[checkType];

  ok(current > valueSnapshot, `${checkType} keeps increasing (${current} > ${valueSnapshot})`);

function assertValueKeptUnchanged(mediaChrome, checkType) {

  assertAttributeDefined(mediaChrome, checkType);

  const valueSnapshot = mediaChrome[checkType];

  // 30ms is long enough to have a low-resolution system clock tick, but short

  // enough to not slow the test down.

  blockMainThread(30);

  const newValue = mediaChrome[checkType];

  timeFuzzyEquals(newValue, valueSnapshot, `${checkType} keeps unchanged (${newValue} vs. ${valueSnapshot})`);

function assertAllProbeRelatedAttributesKeptUnchanged(video) {

  const videoChrome = SpecialPowers.wrap(video);

  assertValueKeptUnchanged(videoChrome, "totalVideoPlayTime");

  assertValueKeptUnchanged(videoChrome, "invisiblePlayTime");

</script>

</head>

<body>

</body>

</html>