chromium/third_party/blink/web_tests/external/wpt/infrastructure/testdriver/actions/popup.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Actions in popup</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<script>
  promise_test((t) => new Promise((resolve, reject) => {
    addEventListener("message", (msg) => {
      if (msg.data === "PASS") {
        resolve();
      } else if (msg.data === "FAIL") {
        reject("actions failed");
      }
    });
    addEventListener("click", (event) => {
      reject("Test window received click meant for the popup");
    });

    let popup = window.open("support/actions.html?popup", "_blank");
    t.add_cleanup(() => popup.close());
  }), "Actions go to the popup and not the test window");
</script>