add benchmark

package.json

@@ -26,6 +26,8 @@
   },
   "devDependencies": {
     "autod": "*",
+    "beautify-benchmark": "~0.2.4",
+    "benchmark": "~1.0.0",
     "istanbul": "*",
     "mocha": "*",
     "should": "*"

test/benchmark/ms.js

@@ -0,0 +1,56 @@
+/**!
+ * humanize-ms - test/benchmark/ms.js
+ *
+ * Copyright(c) node-modules and other contributors.
+ * MIT Licensed
+ *
+ * Authors:
+ *   fengmk2 <m@fengmk2.com> (http://fengmk2.com)
+ */
+
+'use strict';
+
+/**
+ * Module dependencies.
+ */
+
+var Benchmark = require('benchmark');
+var benchmarks = require('beautify-benchmark');
+var originMS = require('ms');
+var ms = require('../..');
+
+var suite = new Benchmark.Suite();
+
+// add tests
+suite
+
+.add('origin ms()', function() {
+  originMS('10s');
+})
+.add('ms()', function() {
+  ms('10s');
+})
+.add('ms(1000)', function() {
+  ms(1000);
+})
+
+// add listeners
+.on('cycle', function (event) {
+  benchmarks.add(event.target);
+})
+.on('start', function () {
+  console.log('\n  node version: %s, date: %s\n  Starting...', process.version, Date());
+})
+.on('complete', function() {
+  benchmarks.log();
+})
+// run async
+.run({ 'async': false });
+
+// node version: v1.6.3, date: Mon Apr 06 2015 11:59:04 GMT+0800 (CST)
+//   Starting...
+//   3 tests completed.
+//
+//   origin ms() x  3,393,695 ops/sec ±1.30% (92 runs sampled)
+//   ms()        x  3,430,360 ops/sec ±1.05% (90 runs sampled)
+//   ms(1000)    x 94,272,966 ops/sec ±1.11% (93 runs sampled)