react: Error: Invariant Violation: findAllInRenderedTree(...): instance must be a composite component

I am writing a test case using Mocha and JSDom.

import React from 'react';
import TestUtils from 'react-addons-test-utils';

describe('ReactOutsideEvent', () => {
    it('captures mousedown event', () => {
        let detachedCoponent;

        detachedCoponent = TestUtils.renderIntoDocument(<div>
            <div className='foo'></div>
        </div>);

        TestUtils.scryRenderedDOMComponentsWithClass(detachedCoponent, 'foo');
    });
});

I’d like to obtain a reference to the generated DOMNode with className “foo”. scryRenderedDOMComponentsWithClass produces:

Error: Invariant Violation: findAllInRenderedTree(...): instance must be a composite component

I have also tried scryRenderedDOMComponentsWithTag and got the same error.

Using 0.14.0-beta3.