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Test Info:

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
section {
margin-bottom: 5px;
}
.target {
background: blue;
width: 100px;
height: 10px;
}
</style>
<body>
<section>
<a href="#">
<div class="target"></div>
</a>
</section>
<section>
<a href="#">
<div class="target" style="z-index: 1"></div>
</a>
</section>
<section>
<a href="#">
<div class="target" style="z-index: -1"></div>
</a>
</section>
<section>
<a href="#">
<div class="target" style="position: relative"></div>
</a>
</section>
<section>
<a href="#">
<div class="target" style="position: relative; z-index: 1"></div>
</a>
</section>
<section>
<a href="#">
<div class="target" style="position: relative; z-index: -1"></div>
</a>
</section>
<script>
function isAncestorOf(target, ancestor) {
for (; target; target = target.parentElement) {
if (target === ancestor)
return true;
}
return false;
}
for (const root of document.getElementsByTagName('section')) {
const target = root.querySelector('.target');
const target_bounds = target.getBoundingClientRect();
const x = target_bounds.x + target_bounds.width / 2;
const y = target_bounds.y + target_bounds.height / 2;
const result = document.elementFromPoint(x, y);
const a = root.querySelector('a');
test(() => {
// For the `<a>` link to work, the `result` must be `a` or its descendant.
assert_true(isAncestorOf(result, a));
}, target.style.cssText);
}
</script>
</body>