css/css-images/image-set/image-set-type-unsupported-rendering-2.html

<!DOCTYPE html>
<title>Image set type rendering</title>
<link rel="author" title="Noam Rosenthal" href="mailto:noam@webkit.org">
<link rel="author" title="Traian Captan" href="mailto:tcaptan@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-images-4/#image-set-notation">
<link rel="match" href="/css/reference/blank.html">
<meta name="assert" content="image-set rendering with all unsupported types">
<!--
Spec definition:
"An image-set() function contains a list of one or more <image-set-option>s,
  and must select only one of them to determine what image it will represent:
  First, remove any <image-set-option>s from the list that specify
  an unknown or unsupported MIME type in their type() value."

If all the values in the image set are of an unsupported type,
the set should be empty.

"This has no effect on the validity of the image-set() function"
-->
<style>
  #test {
    background-image: url("/images/red.png");
    background-image: image-set(
      url("/images/green.png") 1x type('image/unsupported'),
      url("/images/green.png") 1x type('image/unsupported')
    );
    width: 100px;
    height: 100px;
  }
</style>
<div id="test"></div>