css/css-grid/grid-model/grid-floats-no-intrude-001.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Grid Layout Test: floats do not intrude into a grid</title>
<link rel="author" title="Manuel Rego Casasnovas" href="mailto:rego@igalia.com">
<link rel="help" href="http://www.w3.org/TR/css-grid-1/#grid-containers" title="3.1 Establishing Grid Containers">
<link rel="match" href="../../reference/ref-filled-green-100px-square.xht">
<style>
  #reference-overlapped-red {
    position: absolute;
    background-color: red;
    width: 100px;
    height: 100px;
    z-index: -1;
  }

  .test-overlapping-green {
    background-color: green;
    width: 50px;
    height: 100px;
  }

  .float {
    float: left;
  }

  .grid {
    display: grid;
  }
</style>
<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>

<div id="reference-overlapped-red"></div>

<div class="float test-overlapping-green"></div>
<div class="grid test-overlapping-green"></div>