Add a benchmark for changes in enzymejs#490

bench.js

@@ -0,0 +1,35 @@
+var Benchmark = require("benchmark")
+var Enzyme = require(".")
+var React = require("react")
+
+var Component = React.createClass({
+  render() {
+    return React.createElement("section", null, React.createElement("h1",  null), React.createElement("div", null, React.createElement("p", null, "The daily random number is: ", React.createElement("span", { className: "random" }, Math.random()))))
+  }
+})
+
+var wrapper = Enzyme.shallow(React.createElement(Component, null))
+
+function update(wrapper) {
+  wrapper.node = wrapper.renderer.getRenderOutput()
+  wrapper.nodes = [wrapper.node]
+}
+
+console.log()
+console.log(wrapper.text())
+wrapper.instance().setState({hello: 123})
+console.log(wrapper.text()) // <- Should update with the new changes
+console.log()
+
+new Benchmark.Suite()
+  .add(".find('span')", function () {
+    wrapper.find("span")
+  })
+  .add(".find('span') with update", function () {
+    update(wrapper)
+    wrapper.find("span")
+  })
+  .on("cycle", function (event) {
+    console.log(String(event.target))
+  })
+  .run({ async: true })

package.json

@@ -11,6 +11,7 @@
     "version": "npm run build",
     "clean": "rimraf build",
     "lint": "eslint src/** test/**",
+    "bench": "npm run build && node ./bench.js",
     "check": "npm run lint && npm run test:all",
     "build": "babel src --out-dir build",
     "test": "npm run test:only",
@@ -51,6 +52,7 @@
   "author": "Leland Richardson <leland.richardson@airbnb.com>",
   "license": "MIT",
   "dependencies": {
+    "benchmark": "^2.1.0",
     "cheerio": "^0.20.0",
     "is-subset": "^0.1.1",
     "lodash": "^4.13.1",