css/css-env/supports-script.tentative.html

<!DOCTYPE html>
<html>
  <head>
    <link rel="help" href="https://drafts.csswg.org/css-env-1/">
    <title>Test that CSS env vars work with CSS.supports</title>
    <script src="/resources/testharness.js"></script>
    <script src="/resources/testharnessreport.js"></script>
  </head>
  <body>
    <script>
    test(() => {
      assert_true(CSS.supports("background: env(test)"));
      assert_true(CSS.supports("background", "env(test)"));
      assert_true(CSS.supports("background", "env(test, 10px)"));
      assert_true(CSS.supports("background", "foobar(env(test))"));
      assert_false(CSS.supports("background", "env()"));
      assert_false(CSS.supports("background", "env(test,)"));
    });
    </script>
  </body>
</html>