How to test whether a React component is listening to window events

Example:

I have a React Component, List

class List extends React.Component {
  static propTypes {
    onFocusChange: PropTypes.func.isRequired
  }

  componentDidMount() {
    window.addEventListener('keydown', this._handleFocusChange);
  }

  componentWillUnmount() {
    window.removeEventListener('keydown', this._handleFocusChange);
  }

  @autobind
  _handleFocusChange(e) {
    if (e.which === 38) {
      const someValue = populateThisValue();
      this.props.onFocusChange(someValue);
    }
  }
}

Now in the corresponding test file I use React Test Utils sinon spy to mock the onFocusChange function passed in as prop:

test('onFocusChange should be called when up arrow key is clicked', () => {
      const onFocusChange = sinon.stub();
      ReactTestUtils.renderIntoDocument(
        <List
          onFocusChange={onFocusChange}
        />
      );
      ReactTestUtils.Simulate.keyDown(window, { which: 38 });
      assert.isTrue(onFocusChange.calledOnce);
      assert.isTrue(onFocusChange.calledWith(0));
    });

But unfortunately onFocusChange is not being called. I was initially skeptical that componentDidMount() is not being called but I checked and it is.

My guess is that the reference to window that List has is different from the one that is being used in the test.

I am not completely sure how renderIntoDocument() function on React TestUtils actually renders the component and whether its being rendered into window.document.body at all.

Can anyone help me with this?