mozilla-release/testing/web-platform/tests/feature-policy/reporting/sync-xhr-reporting.html

<!DOCTYPE html>
<html>
  <head>
    <script src='/resources/testharness.js'></script>
    <script src='/resources/testharnessreport.js'></script>
  </head>
  <body>
    <script>
var t = async_test("Sync-xhr Report Format");

var check_report_format = (reports, observer) => {
  let report = reports[0];
  assert_equals(report.type, "feature-policy-violation");
  assert_equals(report.url, document.location.href);
  assert_equals(report.body.featureId, "sync-xhr");
  assert_equals(report.body.sourceFile, document.location.href);
  assert_equals(typeof report.body.lineNumber, "number");
  assert_equals(typeof report.body.columnNumber, "number");
  assert_equals(report.body.disposition, "enforce");
};

new ReportingObserver(t.step_func_done(check_report_format),
                      {types: ['feature-policy-violation']}).observe();

t.step_func(() => {
  var xhr = new XMLHttpRequest();
  xhr.open("GET", document.location.href, false);
  assert_throws('NetworkError',
    () => xhr.send(),
    "Synchronous XHR.send should throw an exception when disabled");
})();
    </script>
  </body>
</html>