<!DOCTYPE HTML>
<html>
<body>
<p>Test for isolation caused by a mask. This test passes if the whole rectangle is green.</p>
<svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="400px" height="400px" >
<defs>
  <mask id="msk">
    <rect x="10" y="10" width="20" height="20" fill="rgb(255,255,255)"/>
  </mask>
</defs>
<g transform="scale(4 4)">
  <rect x="0" y="0" width="40" height="40" fill="rgb(0,255,0)"/>
  <g mask="url(#msk)">
    <rect x="10" y="10" width="20" height="20" fill="rgb(0,255,0)" style="mix-blend-mode: difference"/>
  </g>
</g>
</svg>
</body>
</html>