LayoutTests/fast/inline/intrusive-left-right-floats-assert.html

<style>
.box {
  width: 60px;
  height: 30px;
  float: left;
  background-color: blue;
}

.box.right {
  float: right;
  background-color: green;
}
</style>
<div style="width: 100px">
  <div class="box"></div>
  <div class="right box"></div>
  <div>PASS if no assert in debug</div>
</div>
<script>
if (window.testRunner)
  testRunner.dumpAsText();
</script>