LayoutTests/cssom/cssstyledeclaration-csstext-important.html

<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>

<style>
    #box {}
</style>

<div id="box"></div>

<script>
  var style = document.getElementById('box').style;
  test(function(){
      style.cssText = "padding: 10px !important; padding-left: 20px;";
      assert_equals(style.getPropertyValue("padding-left"), "10px");
  }, "padding-left should be taken from the !important property");
</script>