chromium/third_party/blink/web_tests/external/wpt/html/rendering/widgets/button-layout/flex.html

<!doctype html>
<title>button with flex/inline-flex</title>
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<style>
#inline-flex { display: inline-flex }
#flex { display: flex }
#ref > div { display: flex }

#flexstart {
  border: none;
  padding: 0;
  display: flex;
  align-items: flex-start;
  height: 3em;
}

#stretch {
  border: none;
  padding: 0;
  display: flex;
  align-items: stretch;
  height: 3em;
}
</style>
<button id=inline-flex><div>1</div><div>2</div><div>3</div><div>4</div></button>
<button id=flex><div>1</div><div>2</div><div>3</div><div>4</div></button>
<button id=ref><div><div>1</div><div>2</div><div>3</div><div>4</div></div></button>

<div><button id="flexstart"><span id="flexstart-item">abc</span></button></div>

<div><button id="stretch"><span id="stretch-item">abc</span></button></div>
<script>
const ref = document.getElementById('ref');
const expectedWidth = ref.clientWidth;
const expectedHeight = ref.clientHeight;
for (const elm of [document.getElementById('inline-flex'),
                   document.getElementById('flex')]) {
  test(() => {
    // check that flex is supported
    const flexValue = elm.id;
    assert_equals(getComputedStyle(elm).display, flexValue, `${flexValue} is not supported`);
    const width = elm.clientWidth;
    const height = elm.clientHeight;
    assert_equals(width, expectedWidth, 'clientWidth');
    assert_equals(height, expectedHeight, 'clientHeight');
  }, elm.id);
}

// crbug.com/700029
test(() => {
  assert_equals(document.getElementById('flexstart').offsetTop,
    document.getElementById('flexstart-item').offsetTop);
}, 'align-items:flex-start should work');

// crbug.com/1004163
test(() => {
  assert_equals(document.getElementById('stretch').offsetHeight,
    document.getElementById('stretch-item').offsetHeight);
}, 'align-items:stretch should work');
</script>