test: fix test-watch-mode

Refs: #44898
PR-URL: #45585
Reviewed-By: Moshe Atlow <moshe@atlow.co.il>
Reviewed-By: Erick Wendel <erick.workspace@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/sequential/test-watch-mode.mjs

@@ -15,11 +15,16 @@ if (common.isIBMi)
   common.skip('IBMi does not support `fs.watch()`');
 
 const supportsRecursive = common.isOSX || common.isWindows;
+let disableRestart = false;
 
 function restart(file) {
   // To avoid flakiness, we save the file repeatedly until test is done
   writeFileSync(file, readFileSync(file));
-  const timer = setInterval(() => writeFileSync(file, readFileSync(file)), 1000);
+  const timer = setInterval(() => {
+    if (!disableRestart) {
+      writeFileSync(file, readFileSync(file));
+    }
+  }, common.platformTimeout(1000));
   return () => clearInterval(timer);
 }
 
@@ -38,11 +43,15 @@ async function spawnWithRestarts({
   let stdout = '';
   let cancelRestarts;
 
+  disableRestart = true;
   const child = spawn(execPath, ['--watch', '--no-warnings', ...args], { encoding: 'utf8' });
   child.stderr.on('data', (data) => {
     stderr += data;
   });
   child.stdout.on('data', async (data) => {
+    if (data.toString().includes('Restarting')) {
+      disableRestart = true;
+    }
     stdout += data;
     const restartsCount = stdout.match(new RegExp(`Restarting ${printedArgs.replace(/\\/g, '\\\\')}`, 'g'))?.length ?? 0;
     if (restarts === 0 || !isReady(data.toString())) {
@@ -54,6 +63,9 @@ async function spawnWithRestarts({
       return;
     }
     cancelRestarts ??= restart(watchedFile);
+    if (isReady(data.toString())) {
+      disableRestart = false;
+    }
   });
 
   await once(child, 'exit');
@@ -97,9 +109,9 @@ async function failWriteSucceed({ file, watchedFile }) {
 
 tmpdir.refresh();
 
-// Warning: this suite can run safely with concurrency: true
-// only if tests do not watch/depend on the same files
-describe('watch mode', { concurrency: true, timeout: 60_000 }, () => {
+// Warning: this suite cannot run safely with concurrency: true
+// because of the disableRestart flag used for controlling restarts
+describe('watch mode', { concurrency: false, timeout: 60_000 }, () => {
   it('should watch changes to a file - event loop ended', async () => {
     const file = createTmpFile();
     const { stderr, stdout } = await spawnWithRestarts({ file });