With updated deps

tests/App-test.js

@@ -0,0 +1,18 @@
+/** @jsx React.DOM */
+var expect = require('chai').expect;
+
+describe('App', function() {
+  it('has the text Hello world!', function() {
+    var React = require('react/addons');
+    var App = require('../app/App.js');
+    var TestUtils = React.addons.TestUtils;
+
+    var app = TestUtils.renderIntoDocument(
+      <App/>
+    );
+
+    var h1 = TestUtils.findRenderedDOMComponentWithTag(app, 'h1');
+
+    expect(h1.getDOMNode().textContent).to.equal('Hello world!');
+  });
+});