diff --git a/animation-worklet/worklet-animation-cancel-ref.html b/animation-worklet/worklet-animation-cancel-ref.html
new file mode 100644
index 00000000000000..d44927374703ef
--- /dev/null
+++ b/animation-worklet/worklet-animation-cancel-ref.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<title>Reference for Canceling a playing WorkletAnimation should remove the effect</title>
+<style>
+#box {
+  width: 100px;
+  height: 100px;
+  background-color: blue;
+}
+</style>
+
+<div id="box"></div>
diff --git a/animation-worklet/worklet-animation-cancel.https.html b/animation-worklet/worklet-animation-cancel.https.html
new file mode 100644
index 00000000000000..3a28c7515db455
--- /dev/null
+++ b/animation-worklet/worklet-animation-cancel.https.html
@@ -0,0 +1,45 @@
+<html class="reftest-wait">
+<title>Canceling a playing WorkletAnimation should remove the effect</title>
+<link rel="help" href="https://drafts.css-houdini.org/css-animationworklet/">
+<meta name="assert" content="Canceling a playing animation should remove the effect">
+<link rel="match" href="worklet-animation-cancel-ref.html">
+
+<script src="/web-animations/testcommon.js"></script>
+<script src="/common/reftest-wait.js"></script>
+<script src="common.js"></script>
+
+<style>
+  #box {
+    width: 100px;
+    height: 100px;
+    background-color: blue;
+  }
+</style>
+
+<div id="box"></div>
+
+<script>
+  registerConstantLocalTimeAnimator(500).then(_ => {
+    const box = document.getElementById('box');
+    const effect = new KeyframeEffect(box,
+      [
+        {transform: 'translateY(0)'},
+        {transform: 'translateY(200px)'}
+      ], {
+        duration: 1000,
+        iterations: Infinity
+      }
+    );
+
+    const animation = new WorkletAnimation('constant_time', effect);
+    animation.play();
+
+    waitForAsyncAnimationFrames(1).then(_ => {
+      // Canceling a playing animation should remove the effect.
+      animation.cancel();
+      waitForAsyncAnimationFrames(1).then(_ => {
+        takeScreenshot();
+      });
+    });
+  });
+</script>
diff --git a/animation-worklet/worklet-animation-creation.https.html b/animation-worklet/worklet-animation-creation.https.html
new file mode 100644
index 00000000000000..3e403feb436645
--- /dev/null
+++ b/animation-worklet/worklet-animation-creation.https.html
@@ -0,0 +1,126 @@
+<!DOCTYPE html>
+<title>Verify that WorkletAnimation is correctly created</title>
+<link rel="help" href="https://drafts.css-houdini.org/css-animationworklet/">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/web-animations/testcommon.js"></script>
+<script src="common.js"></script>
+
+<style>
+  .scroller {
+    height: 100px;
+    width: 100px;
+    overflow: scroll;
+  }
+  .content {
+    height: 500px;
+    width: 500px;
+  }
+</style>
+
+<script>
+function CreateKeyframeEffect(element) {
+  return new KeyframeEffect(
+      element,
+      [
+        { transform: 'translateY(0%)' },
+        { transform: 'translateY(100%)' }
+      ],
+      { duration: 3000, fill: 'forwards' }
+  );
+}
+</script>
+<script id="simple_animate" type="text/worklet">
+  registerAnimator("test-animator", class {
+    animate(currentTime, effect) {}
+  });
+</script>
+
+<div id='element'></div>
+<div id='element2'></div>
+<div class='scroller'>
+  <div class='content'></div>
+</div>
+
+<script>
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+    let workletAnimation = new WorkletAnimation('test-animator', effect);
+    assert_equals(workletAnimation.playState, 'idle');
+    assert_equals(workletAnimation.timeline, document.timeline);
+  }, 'WorkletAnimation creation without timeline should use default documentation timeline');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+    let workletAnimation = new WorkletAnimation('test-animator', effect);
+    assert_equals(workletAnimation.playState, 'idle');
+  }, 'WorkletAnimation creation with timeline should work');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+    let options = { my_param: 'foo', my_other_param: true };
+    let workletAnimation = new WorkletAnimation(
+        'test-animator', effect, document.timeline, options);
+    assert_equals(workletAnimation.playState, 'idle');
+  }, 'WorkletAnimation creation with timeline and options should work');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+    let scroller = document.querySelector('.scroller');
+    let scrollTimeline = new ScrollTimeline(
+        { scrollSource: scroller, timeRange: 100, orientation: 'inline' });
+    let workletAnimation = new WorkletAnimation(
+        'test-animator', effect, scrollTimeline);
+    assert_equals(workletAnimation.playState, 'idle');
+  }, 'ScrollTimeline is a valid timeline for a WorkletAnimation');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let constructorFunc = function() { new WorkletAnimation(
+        'test-animator', []); };
+    assert_throws('NotSupportedError', constructorFunc);
+  }, 'If there are no effects specified, object construction should fail');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+
+    let otherDoc = document.implementation.createHTMLDocument();
+    let otherElement = otherDoc.createElement('div');
+    otherDoc.body.appendChild(otherElement);
+    let otherEffect = CreateKeyframeEffect(otherElement);
+
+    let constructorFunc = function() { new WorkletAnimation(
+        'test-animator', [ effect, otherEffect ]); };
+    assert_throws('NotSupportedError', constructorFunc);
+  }, 'If the effects are from different documents, object construction should fail');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    // TODO(crbug.com/781816): Allow KeyframeEffects with no target in AnimationWorklet.
+    let effect = CreateKeyframeEffect(null);
+    let effect2 = CreateKeyframeEffect(document.querySelector('#element'));
+
+    let constructorFunc = function() { new WorkletAnimation(
+        'test-animator', [ effect, effect2 ]); };
+    assert_throws('NotSupportedError', constructorFunc);
+
+    let constructorFunc2 = function() { new WorkletAnimation(
+        'test-animator', [ effect2, effect ]); };
+    assert_throws('NotSupportedError', constructorFunc2);
+  }, 'If an effect has no target, object construction should fail');
+
+  promise_test(async t => {
+    await runInAnimationWorklet(document.getElementById('simple_animate').textContent);
+    let effect = CreateKeyframeEffect(document.querySelector('#element'));
+    let constructorFunc = function() {
+        new WorkletAnimation('unregistered-animator', effect);
+    };
+    assert_throws('InvalidStateError', constructorFunc);
+  }, 'Constructing worklet animation for unregisested animator should throw');
+</script>
diff --git a/animation-worklet/worklet-animation-duration-ref.html b/animation-worklet/worklet-animation-duration-ref.html
new file mode 100644
index 00000000000000..81b01bdca813ca
--- /dev/null
+++ b/animation-worklet/worklet-animation-duration-ref.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<title>Reference for WorkletAnimation should continue to be in effect forever, even if its duration is passed</title>
+<style>
+#box {
+  width: 100px;
+  height: 100px;
+  background-color: green;
+  transform: translateY(100px);
+}
+</style>
+
+<div id="box"></div>
diff --git a/animation-worklet/worklet-animation-duration.https.html b/animation-worklet/worklet-animation-duration.https.html
new file mode 100644
index 00000000000000..1526004eaf17d5
--- /dev/null
+++ b/animation-worklet/worklet-animation-duration.https.html
@@ -0,0 +1,40 @@
+<html>
+<title>WorkletAnimation should continue to be in effect forever, even if its duration is passed</title>
+<link rel="help" href="https://drafts.css-houdini.org/css-animationworklet/">
+<link rel="match" href="worklet-animation-duration-ref.html">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/web-animations/testcommon.js"></script>
+<script src="common.js"></script>
+
+<div id="box"></div>
+
+<script>
+  promise_test(async t => {
+    await registerConstantLocalTimeAnimator(0.5);
+
+    const box = document.getElementById('box');
+    const effect = new KeyframeEffect(box,
+      [
+        {transform: 'translateY(0px)' },
+        {transform: 'translateY(200px)' }
+      ], {
+        duration: 1,
+      }
+    );
+
+    const animation = new WorkletAnimation('constant_time', effect);
+    animation.play();
+
+    let expected_transform = "matrix(1, 0, 0, 1, 0, 100)";
+    await waitForAnimationFrameWithCondition(_ => {
+      return getComputedStyle(box).transform == expected_transform;
+    });
+
+    // The animation is specified to last for 1 millisecond
+    await new Promise(resolve => step_timeout(resolve, 500));
+
+    assert_equals(getComputedStyle(document.getElementById("box")).transform, expected_transform);
+  }, "WorkletAnimation should continue to be in effect forever, even if its duration is passed");
+</script>
diff --git a/animation-worklet/worklet-animation-start-delay-ref.html b/animation-worklet/worklet-animation-start-delay-ref.html
new file mode 100644
index 00000000000000..efef6f842bf0f9
--- /dev/null
+++ b/animation-worklet/worklet-animation-start-delay-ref.html
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<title>Reference for WorkletAnimation should respect delay given in options</title>
+<style>
+.box {
+  width: 100px;
+  height: 100px;
+  background-color: green;
+}
+</style>
+
+<div class="box"></div>
+<div style="transform: translateX(100px);" class="box"></div>
diff --git a/animation-worklet/worklet-animation-start-delay.https.html b/animation-worklet/worklet-animation-start-delay.https.html
new file mode 100644
index 00000000000000..c8683f7daccb40
--- /dev/null
+++ b/animation-worklet/worklet-animation-start-delay.https.html
@@ -0,0 +1,64 @@
+<html class="reftest-wait">
+<title>WorkletAnimation should respect delay given in options</title>
+<link rel="help" href="https://drafts.css-houdini.org/css-animationworklet/">
+<meta name="assert" content="Worklet Animation should respect delay given in options">
+<link rel="match" href="worklet-animation-start-delay-ref.html">
+
+<script src="/web-animations/testcommon.js"></script>
+<script src="/common/reftest-wait.js"></script>
+<script src="common.js"></script>
+
+<style>
+  .box {
+    width: 100px;
+    height: 100px;
+    background-color: green;
+  }
+</style>
+
+<div id="t0" class="box"></div>
+<div id="t1" class="box"></div>
+<div id="out"></div>
+<script id="visual_update"  type="text/worklet">
+  registerAnimator("t0_animator", class {
+    animate(currentTime, effect) {
+      effect.localTime = 500;
+    }
+  });
+
+  registerAnimator("t1_animator", class {
+    animate(currentTime, effect) {
+      effect.localTime = 5500;
+    }
+  });
+</script>
+
+<script>
+  runInAnimationWorklet(
+    document.getElementById('visual_update').textContent
+  ).then(()=>{
+    const keyframes = [
+      {transform: 'translateX(0)' },
+      {transform: 'translateX(200px)' }
+    ];
+    const options = {
+      duration: 1000,
+      delay: 5000,
+    };
+
+    const $t0 = document.getElementById('t0');
+    const $t0_effect = new KeyframeEffect($t0, keyframes, options);
+    const $t0_animation = new WorkletAnimation('t0_animator', $t0_effect);
+
+    const $t1 = document.getElementById('t1');
+    const $t1_effect = new KeyframeEffect($t1, keyframes, options);
+    const $t1_animation = new WorkletAnimation('t1_animator', $t1_effect);
+
+    $t0_animation.play();
+    $t1_animation.play();
+
+    waitForAsyncAnimationFrames(1).then(_ => {
+      takeScreenshot();
+    });
+  });
+</script>
