mozilla-release/testing/web-platform/tests/trusted-types/TrustedTypePolicyFactory-createPolicy-nameTests.tentative.https.html

<!DOCTYPE html>
<script src="/resources/testharness.js" ></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/helper.sub.js"></script>
<meta http-equiv="Content-Security-Policy"
      content="trusted-types SomeName SomeOtherName">
<body>
<script>
  // Policy name test
  test(t => {
    let policy = trustedTypes.createPolicy('SomeName', {} );
    assert_true(policy instanceof TrustedTypePolicy);
    assert_equals(policy.name, 'SomeName');
  }, "policy.name = name");

  // Duplicate names test
  test(t => {
    assert_throws_js(TypeError, _ => {
     trustedTypes.createPolicy('SomeName', {} );
    });
  }, "duplicate policy name attempt throws");

  // Check error messages.
  test(t => {
    try {
      trustedTypes.createPolicy("unknown name", {});
    } catch (e) {
      assert_true(e.toString().includes("disallowed"));
      assert_false(e.toString().includes("already exists"));
    }

    try {
      trustedTypes.createPolicy("SomeName", {});
    } catch (e) {
      assert_false(e.toString().includes("disallowed"));
      assert_true(e.toString().includes("already exists"));
    }
  }, "Error messages for duplicates and unlisted policies should be different");

</script>