chromium/third_party/blink/web_tests/external/wpt/infrastructure/testdriver/click_nested.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>TestDriver click method with multiple windows and nested iframe</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>

<iframe src="about:blank"></iframe>

<script>
setup({single_test: true});

window.open("about:blank")
var child = window.open("click_outer_child.html")
window.open("about:blank")

addEventListener("load",() => {
    child.addEventListener("load", () => {
        let doc = child.frames[2].document;
        let button = doc.getElementById("button");
        test_driver
            .click(button)
            .then(() => {
                assert_equals(doc.getElementById("log").textContent, "PASS");
                done();
            })
            .catch(() => assert_unreached("click failed"));
    });
});
</script>