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chromium/third_party/blink/web_tests/fast/workers/chromium/dedicated-worker-error-event.html 

<!doctype html>
<meta charset=utf-8>
<title>Dedicated Worker: Error event error message</title>
<script src='../../../resources/testharness.js'></script>
<script src='../../../resources/testharnessreport.js'></script>
<script>
// TODO(yiyix): This test will be superseded by
// external/wpt/workers/Worker_ErrorEvent_error.htm once
// https://crbug.com/708857 is fixed.
promise_test(t => {
    return new Promise(resolve => {
          var worker = new Worker('resources/error-script.js');
          worker.onmessage = resolve;
        })
      .then(e => assert_equals(e.data.value, 'testError'));
  }, 'Error handlers inside a worker should see the error value');
</script>