chromium/third_party/blink/web_tests/external/wpt/credential-management/support/otpcredential-iframe.html

<!doctype html>
<script type="module">
import {Status, expectOTPRequest} from './otpcredential-helper.js';

// Loading otpcredential-iframe.html in the test will make an OTPCredentials
// call on load, and trigger a postMessage upon completion.
//
// message {
//   string result: "Pass" | "Fail"
//   string code: credentials.code
//   string errorType: error.name
// }

window.onload = async () => {
  try {
    await expectOTPRequest().andReturn(
        () => ({status: Status.SUCCESS, otp: "ABC123"}));
    const credentials =
        await navigator.credentials.get({otp: {transport: ["sms"]}});
    window.parent.postMessage({result: "Pass", code: credentials.code}, '*');
  } catch (error) {
    window.parent.postMessage({result: "Fail", errorType: error.name}, '*');
  }
}

</script>