test: increase test coverage for fs.promises read

PR-URL: #22800
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

test/parallel/test-fs-promises.js

@@ -64,6 +64,13 @@ function verifyStatObject(stat) {
   assert.strictEqual(typeof stat.mode, 'number');
 }
 
+async function getHandle(dest) {
+  await copyFile(fixtures.path('baz.js'), dest);
+  await access(dest, 'r');
+
+  return open(dest, 'r+');
+}
+
 {
   async function doTest() {
     tmpdir.refresh();
@@ -93,6 +100,19 @@ function verifyStatObject(stat) {
     await handle.datasync();
     await handle.sync();
 
+    // test fs.read promises when length to read is zero bytes
+    {
+      const dest = path.resolve(tmpDir, 'test1.js');
+      const handle = await getHandle(dest);
+      const buf = Buffer.from('DAWGS WIN');
+      const bufLen = buf.length;
+      await handle.write(buf);
+      const ret = await handle.read(Buffer.alloc(bufLen), 0, 0, 0);
+      assert.strictEqual(ret.bytesRead, 0);
+
+      await unlink(dest);
+    }
+
     const buf = Buffer.from('hello fsPromises');
     const bufLen = buf.length;
     await handle.write(buf);
@@ -203,13 +223,22 @@ function verifyStatObject(stat) {
 
     await unlink(newLink2);
 
-    const newdir = path.resolve(tmpDir, 'dir');
-    await mkdir(newdir);
-    stats = await stat(newdir);
-    assert(stats.isDirectory());
-    const list = await readdir(tmpDir);
-    assert.deepStrictEqual(list, ['baz2.js', 'dir']);
-    await rmdir(newdir);
+    // testing readdir lists both files and directories
+    {
+      const newDir = path.resolve(tmpDir, 'dir');
+      const newFile = path.resolve(tmpDir, 'foo.js');
+
+      await mkdir(newDir);
+      await writeFile(newFile, 'DAWGS WIN!', 'utf8');
+
+      stats = await stat(newDir);
+      assert(stats.isDirectory());
+      const list = await readdir(tmpDir);
+      assert.notStrictEqual(list.indexOf('dir'), -1);
+      assert.notStrictEqual(list.indexOf('foo.js'), -1);
+      await rmdir(newDir);
+      await unlink(newFile);
+    }
 
     // mkdir when options is number.
     {