chromium/third_party/blink/web_tests/external/wpt/trusted-types/Element-toggleAttribute.html

<!DOCTYPE html>
<head>
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
  <meta http-equiv="Content-Security-Policy" content="require-trusted-types-for 'script'">
</head>
<body>
<div>
  <p id="p" onclick="alert(1)"></p>
  <iframe id="iframe" srcdoc="abc"></iframe>
</div>
<script>
  // Regression test for crbug.com/341057803.
  // This tests that TT doesn't interfere with regular DOM behaviour, and so
  // these tests should pass on any browser, whether they support TT or not.

  test(t => {
    const elem = document.getElementById("p");
    elem.toggleAttribute("onclick");
    assert_false(elem.hasAttribute("onclick"));
    elem.toggleAttribute("onclick");
    assert_true(elem.hasAttribute("onclick"));
  }, "TT should not interfere with toggleAttribute on an event handler");

  test(t => {
    const elem = document.getElementById("iframe");
    elem.toggleAttribute("srcdoc");
    assert_false(elem.hasAttribute("srcdoc"));
    elem.toggleAttribute("srcdoc");
    assert_true(elem.hasAttribute("srcdoc"));
  }, "TT should not interfere with toggleAttribute on an iframe srcdoc");
</script>
</body>