chromium/third_party/blink/web_tests/fast/css-grid-layout/implicit-columns-auto-resolution.html

<!DOCTYPE html>
<html>
<link href="resources/grid.css" rel="stylesheet">
<link href="resources/grid-alignment.css" rel="stylesheet">
<style>
.gridAutoContent {
    /* grid-template-columns is left unset so that the grid item's column is implicit. */
    grid-template-rows: 50px;
}

.firstRowFirstColumn {
    font: 10px/1 Ahem;
    /* Make us fit our grid area. */
    width: 100%;
    height: 100%;
}
</style>
<script src="../../resources/check-layout.js"></script>
<body onload="checkLayout('.gridAutoContent');">

<p>Test that resolving auto tracks on grid items works properly.</p>

<div class="constrainedContainer">
    <div class="grid gridAutoContent">
        <div class="firstRowFirstColumn" data-expected-width="30" data-expected-height="50">XXX XXX XXX</div>
    </div>
</div>

<!-- Allow the extra logical space distribution to occur. -->
<div style="width: 40px; height: 10px">
    <div class="grid gridAutoContent">
        <div class="firstRowFirstColumn" data-expected-width="40" data-expected-height="50">XX XX XX XX XX XX</div>
    </div>
</div>

<div style="width: 100px; height: 10px;">
    <div class="grid gridAutoContent justifyContentStart">
        <div class="firstRowFirstColumn" data-expected-width="50" data-expected-height="50">XXXXX</div>
    </div>
</div>

</body>
</html>