<!DOCTYPE html>
<title>position:sticky elements can be constrained by top and bottom exceeding container size</title>
<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
<meta name="assert" content="This test checks that position:sticky elements obey both top and bottom constraints" />

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>

.scroller {
  height: 200px;
  overflow: auto;
  position: relative;
}
.container {
  height: 120px;
}
.padding, .sticky {
  height: 50px;
}
.overflow-padding {
  height: 200px;
}
.sticky {
  position: sticky;
  background: green;
  top: -25px;
  bottom: 150px;
}
</style>

<body>
  <div class="scroller">
    <div class="container">
      <div class="padding"></div>
      <div class="sticky"></div>
    </div>
    <div class="overflow-padding"></div>
  </div>
</body>

<script>
test(() => {
  const scroller = document.querySelector('.scroller');
  const element = document.querySelector('.sticky');
  scroller.scrollTop = 0;
  assert_equals(element.offsetTop, 0);
}, 'initially the sticky box should be pushed to the top of the container');

test(() => {
  const scroller = document.querySelector('.scroller');
  const element = document.querySelector('.sticky');
  scroller.scrollTop = 95;
  assert_equals(element.offsetTop, 70);
}, 'when we scroll past the flow position the top constraint pushes it down');
</script>
