<!DOCTYPE html> <meta charset="utf-8"> <title>CSS Transitions Test: transition-property - border-left-width</title> <link rel="author" title="Intel" href="http://www.intel.com"> <link rel="author" title="Shiyou Tan" href="mailto:shiyoux.tan@intel.com"> <link rel="help" href="https://drafts.csswg.org/web-animations-1/#animation-type"> <link rel="help" href="https://drafts.csswg.org/css-backgrounds-3/#the-border-width"> <meta name="assert" content="Test checks that the 'border-left-width' property is animatable."> <style> #test { border: 5px solid blue; height: 90px; transition-duration: 2s; transition-property: border-left-width; transition-timing-function: linear; width: 90px; } </style> <body> <p>Click the square with blue border below. Test passes if the width of left border grows gradually not immediately until it stops.</p> <div id="test"></div> <script> (function() { var div = document.querySelector("#test"); div.addEventListener("click", function(evt) { div.setAttribute("style", "border-left-width: 20px;"); }, false); })(); </script> </body>