test: use tmpDir instead of fixtures in readdir

This patch

 - makes the test use tmp directory instead of the fixtures directory,
 - simplifies the code
 - moves the test to `parallel`.

PR-URL: #2587

Reviewed-By: Rich Trott <rtrott@gmail.com>

test/parallel/test-fs-readdir.js

@@ -0,0 +1,36 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const path = require('path');
+const fs = require('fs');
+
+const readdirDir = common.tmpDir;
+const files = ['empty', 'files', 'for', 'just', 'testing'];
+
+// Make sure tmp directory is clean
+common.refreshTmpDir();
+
+// Create the necessary files
+files.forEach(function(currentFile) {
+  fs.closeSync(fs.openSync(readdirDir + '/' + currentFile, 'w'));
+});
+
+// Check the readdir Sync version
+assert.deepEqual(files, fs.readdirSync(readdirDir).sort());
+
+// Check the readdir async version
+fs.readdir(readdirDir, common.mustCall(function(err, f) {
+  assert.ifError(err);
+  assert.deepEqual(files, f.sort());
+}));
+
+// readdir() on file should throw ENOTDIR
+// https://github.com/joyent/node/issues/1869
+assert.throws(function() {
+  fs.readdirSync(__filename);
+}, /Error: ENOTDIR: not a directory/);
+
+fs.readdir(__filename, common.mustCall(function(e) {
+  assert.equal(e.code, 'ENOTDIR');
+}));