starting-style-rule-pseudo-elements.html

<!DOCTYPE html>
<title>CSS Transitions Test: @starting-style for pseudo elements</title>
<link rel="help" href="https://drafts.csswg.org/css-transitions-2/#defining-before-change-style-the-starting-style-rule">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/css-transitions/support/helper.js"></script>
<div id="target" class="trans"></div>
<style>
  #target::before {
    transition-property: background-color, color;
    transition-duration: 100s;
    transition-timing-function: steps(2, start);
    color: green;
    background-color: white;
    content: "";
  }
  @starting-style {
    #target::before {
      background-color: black;
    }
  }
  #target.red::before {
    background-color: red;
  }
</style>
<script>
  promise_test(async t => {
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target, "::before").color, "rgb(0, 128, 0)",
                  "No transition of color");
    assert_equals(getComputedStyle(target, "::before").backgroundColor, "rgb(128, 128, 128)",
                  "Background transition from @starting-style value black to white");
  }, "Triggered transition from first style update");

  promise_test(async t => {
    target.style.display = "none";
    target.className = "red";
    assert_equals(getComputedStyle(target, "::before").backgroundColor, "rgb(255, 0, 0)",
                  "Overridden with red. No transition while display:none");
    target.className = "";
    assert_equals(getComputedStyle(target, "::before").backgroundColor, "rgb(255, 255, 255)",
                  "Removing class while display:none. Still no transition");
    await waitForAnimationFrames(2);
    target.style.display = "block";
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target, "::before").backgroundColor, "rgb(128, 128, 128)",
                  "Background transition from @starting-style value black to white");
  }, "Triggered transition from display:none to display:block");

  promise_test(async t => {
    let removed = target;
    removed.remove();
    await waitForAnimationFrames(2);
    document.body.appendChild(removed);
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target, "::before").backgroundColor, "rgb(128, 128, 128)",
                  "Background transition from @starting-style value black to white");
  }, "Triggered transition on DOM insertion");
</script>
chromium/third_party/blink/web_tests/external/wpt/css/css-transitions/starting-style-rule-pseudo-elements.html
