test: simplify start and update tests

lib/internal/fs/watch/linux.js

@@ -23,25 +23,18 @@ function lazyLoadFsSync() {
   return internalSync;
 }
 
-async function traverse(dir, parent = undefined, files = new SafeMap()) {
-  const { readdir, stat } = lazyLoadFsPromises();
+async function traverse(dir, files = new SafeMap()) {
+  const { readdir } = lazyLoadFsPromises();
 
   const filenames = await readdir(dir, { withFileTypes: true });
 
-  if (parent !== undefined) {
-    files.set(dir, parent);
-  } else {
-    // Optimization: Only call `stat` on the root element.
-    files.set(dir, await stat(dir));
-  }
-
   for await (const file of filenames) {
     const f = path.join(dir, file.name);
 
     files.set(f, file);
 
     if (file.isDirectory()) {
-      await traverse(f, file, files);
+      await traverse(f, files);
     }
   }
 
@@ -168,9 +161,12 @@ class FSWatcher extends EventEmitter {
   }
 
   async [kFSWatchStart](filename) {
+    const { stat } = lazyLoadFsPromises();
+
     this.#rootPath = filename;
     this.#closed = false;
     this.#files = await traverse(filename);
+    this.#files.set(filename, await stat(filename));
 
     for (const f of this.#files.keys()) {
       this.#watchFile(f);

test/parallel/test-bootstrap-modules.js

@@ -67,6 +67,7 @@ const expectedModules = new Set([
   'NativeModule internal/fs/read_file_context',
   'NativeModule internal/fs/rimraf',
   'NativeModule internal/fs/utils',
+  'NativeModule internal/fs/watch/linux',
   'NativeModule internal/fs/watchers',
   'NativeModule internal/heap_utils',
   'NativeModule internal/histogram',