<html>
<style>
div {
  background: red;
  width: 100px;
  height: 100px;
}
@media print {
  div {
    background: green;
  }
  span {
    font-style: italic;
  }
}
</style>
<script>
  if (window.testRunner)
    testRunner.setPrinting();
</script>
<body>
  <div></div>
  <span>When printing, you should see a green square above and this text should be italic.</span>
</body>
</html>