<!DOCTYPE html>
<html lang="en-US">
<head>
<title>test of border-image-source: linear-gradient</title>
<style>
div.border {
  border: 30px solid black;
  border-image: linear-gradient(to bottom right, red, blue);
  width: 180px;
  height: 180px;
}
</style>
</head>
<body>
<div class="border"></div>
</body>
</html>