<!DOCTYPE html>
<title>position:sticky should operate correctly for the root scroller</title>
<link rel="help" href="https://drafts.csswg.org/css-position-3/#valdef-position-sticky">
<link rel="help" href="https://drafts.csswg.org/cssom-view/#propdef-scroll-behavior">
<meta name="assert" content="This test checks that position:sticky elements work when using the root (document) scroller which has `scroll-behavior` property" />

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/scroll-behavior.js"></script>

<style>
html {
  scroll-behavior: smooth;
}

body {
  /* Assumption: 3000px is taller than any user agents test window size. */
  height: 3000px;
  /* A property which propagates for <html>. */
  overflow-x: hidden;
}

#sticky {
  position: sticky;
  top: 50px;
  width: 200px;
  height: 200px;
  background-color: green;
}
</style>

<div id="sticky">This is a sticky element!</div>

<script>
promise_test(async () => {
  window.scrollTo(0, 700);

  await waitForScrollEnd(document.scrollingElement);

  assert_equals(sticky.offsetTop, 700 + 50);
}, 'Sticky elements work with the root (document) scroller');
</script>