css/css-layout-api/computed-style-layout-function.https.html

<!DOCTYPE html>
<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#valdef-display-layout">
<meta name="assert" content="This test checks that a layout() function parses correctly and serializes correctly from computed style." />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#test1 { display: layout(test1); }
#test2 { display: layout(); }
#test3 { display: layout(test3, invalid); }
#test4 { --display: layout(test4); display: var(--display); }
</style>

<div id=test1></div>
<div id=test2></div>
<div id=test3></div>
<div id=test4></div>
<div id=test5></div>
<script>
test(function() {
  const test1 = document.getElementById('test1');
  assert_equals(getComputedStyle(test1).display, 'layout(test1)');
});

test(function() {
  // layout() should fail to parse.
  const test2 = document.getElementById('test2');
  assert_equals(getComputedStyle(test2).display, 'block');
});

test(function() {
  // layout(test3, invalid) should fail to parse.
  const test3 = document.getElementById('test3');
  assert_equals(getComputedStyle(test3).display, 'block');
});

test(function() {
  // Setting via a custom property should work.
  const test4 = document.getElementById('test4');
  assert_equals(getComputedStyle(test4).display, 'layout(test4)');
});

test(function() {
  // Setting the inline style should reflect in the computed style.
  const test5 = document.getElementById('test5');
  assert_equals(getComputedStyle(test5).display, 'block');

  test5.style.display = 'layout(test5)';
  assert_equals(getComputedStyle(test5).display, 'layout(test5)');
});
</script>