<!DOCTYPE html>
<title>Basic :is/:where matching behavior</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://drafts.csswg.org/selectors-4/#matches">

<main id=main>
  <div id=a><div id=d></div></div>
  <div id=b><div id=e></div></div>
  <div id=c><div id=f></div></div>
</main>

<script>
  function formatElements(elements) {
    return elements.map(e => e.id).sort().join();
  }

  // Test that |selector| returns the given elements in #main.
  function test_selector(selector, expected) {
    test(function() {
      let actual = Array.from(main.querySelectorAll(selector));
      assert_equals(formatElements(actual), formatElements(expected));
    }, `${selector} matches expected elements`);
  }

  test_selector(':is()', []);
  test_selector(':is(#a)', [a]);
  test_selector(':is(#a, #f)', [a, f]);
  test_selector(':is(#a, #c) :where(#a #d, #c #f)', [d, f]);
  test_selector('#c > :is(#c > #f)', [f]);
  test_selector('#c > :is(#b > #f)', []);
  test_selector('#a div:is(#d)', [d]);
  test_selector(':is(div) > div', [d, e, f]);
  test_selector(':is(*) > div', [a, b, c, d, e, f]);
  test_selector(':is(*) div', [a, b, c, d, e, f]);
  test_selector('div > :where(#e, #f)', [e, f]);
  test_selector('div > :where(*)', [d, e, f]);
  test_selector(':is(*) > :where(*)', [a, b, c, d, e, f]);
  test_selector(':is(#a + #b) + :is(#c)', [c]);
  test_selector(':is(#a, #b) + div', [b, c]);
</script>