testing/web-platform/tests/navigation-timing/resources/secure-connection-test.html

<!doctype html>
<script>
const entries =  performance.getEntriesByType("navigation");
if (!entries) {
  window.top.postMessage("FAIL - not supported", "*");
}
const entry = entries[0];
if (entry.secureConnectionStart != entry.fetchStart) {
  window.top.postMessage("FAIL - unexpected secureConnectionStart value of " +
    entry.secureConnectionStart + " does not equal " + entry.fetchStart, "*");
}
window.top.postMessage("PASS", "*");
</script>