fixup! test: add opt-in process WPT runner

Author: panva

test/parallel/test-common-wpt-webworker-error.js

@@ -47,37 +47,33 @@ check('process', () => {
 
 function check(backend, start) {
   const { runner, stop } = start();
-  let sawResult = false;
 
   const timeout = setTimeout(() => {
     stop();
     assert.fail(`WPT worker error was not reported on the ${backend} backend`);
   }, common.platformTimeout(1000));
 
+  const onCompletion = common.mustCall((status) => {
+    clearTimeout(timeout);
+    assert.strictEqual(status.status, 1);
+    assert.strictEqual(status.message, 'probe error after first result');
+    stop();
+  });
+
   runner.on('error', common.mustNotCall());
-  runner.on('message', common.mustCall((message) => {
+  // The error reaches the runner straight from the Web Worker while results
+  // travel through the harness, so it can arrive before them.
+  runner.on('message', common.mustCallAtLeast((message) => {
     switch (message.type) {
       case 'result':
         assert.strictEqual(message.result.name, 'reported before error');
         assert.strictEqual(message.result.status, 0);
-        sawResult = true;
         break;
       case 'completion':
-        clearTimeout(timeout);
-        assert.strictEqual(message.status.status, 1);
-        assert.strictEqual(
-          message.status.message,
-          'probe error after first result',
-        );
-        stop();
+        onCompletion(message.status);
         break;
       default:
         assert.fail(`Unexpected message type: ${message.type}`);
     }
-  }, 2));
-
-  process.on('exit', () => {
-    assert.ok(sawResult,
-              `the result reported before the error was not forwarded on the ${backend} backend`);
-  });
+  }, 1));
 }