Error 'h1.findDOMNode is not a function' when running a Karma test

I am trying to write a simple test. I have Karma as the test runner and Mocha as the framework.

Each time I run the test, it fails with the error... TypeError: h1.findDOMNode is not a function

Here's the test script...

// Article-test.jsx
var React = require('react'),
    TestUtils = require('react-addons-test-utils'),
    expect = require('expect'),
    Article = require('../Article.jsx');

it("renders an h1", function () {
    var article = TestUtils.renderIntoDocument(
        <Article />
    );

    var h1 = TestUtils.findRenderedDOMComponentWithTag(
        article, 'h1'
    );

    expect(h1.findDOMNode().textContent).toEqual("Example Title");
});

This was after finding that getDOMNode is deprecated, and is now findDOMNode. I keep finding out methods which have been deprecated.

react + react-addons-test-utils ver. 15.0.1 | mocha ver. 2.4.5

Try

expect(h1.textContent).toEqual("Example Title");