chromium/third_party/blink/web_tests/external/wpt/css/css-flexbox/flex-item-position-relative-001.html

<!DOCTYPE html>
<title>Flex items and `position: relative`</title>
<link rel="author" title="Martin Robinson" href="mailto:[email protected]">
<link rel="help" href="https://drafts.csswg.org/css-position/#position-property">
<meta name="assert"
  content="Flex items can be positioned with `position: relative` and establish containing blocks for absolutely-positioned descendants." />
<link rel="match" href="flex-item-position-relative-001-ref.html">

<style>
    body {
        margin: 0;
    }
    #flex {
        display: flex;
        width: 100px;
        height: 100px;
    }

    #flex > div {
        width: 50px;
        height: 50px;
        background: green;
        position: relative;
        top: 50px;
        left: 50px;
    }
    #flex > div > div {
        width: 50px;
        height: 50px;
        background: green;
        position: absolute;
        left: 100%;
        top: 100%;
    }
</style>

<div style="position: absolute; background: red; width: 50px; height: 50px; left: 50px; top: 50px"></div>

<div style="position: absolute; background: red; width: 50px; height:50px; left: 100px; top: 100px"></div>
<div id="flex">
    <div><div style="background: green"></div></div>
</div>