chromium/third_party/blink/web_tests/fast/alignment/alignment-and-anomymous-boxes-expected.html

<!DOCTYPE html>

<style>
.container {
   background: grey;
   width: 200px;
   height: 100px;
}
.grid { display: grid; }
.flex { display: flex; }
.selfCenter {
   align-self: center;
   justify-self: center;
}
</style>

<p>Grid item created as anonymous box to contain the text element. The text element should be centered in both axis due to the Default Alignment 'center' value on its container.</p>
<div class="container grid">
    <div class="selfCenter">foobar</div>
</div>

<p>Flex item created as anonymous box to contain the text element. The text element should be centered in cross axis due to the Default Alignment 'center' value on its container.</p>
<div class="container flex">
    <div class="selfCenter">foobar</div>
</div>