How to mock e.preventDefault in react component's child

Try this

link.simulate('click', {
  preventDefault: () => {
  }
 });

 test('simulates click events', () => {
    const e = { stopPropagation: jest.fn() };
    const component = shallow(<ListItem{...props} />);
    const li = component.find('li').at(0).childAt(0)
    li.props().onClick(e)

    expect();
  });

Just to note that this is an issue only when using shallow enzyme renderer. In case of full DOM renderer mount, the event object contains the preventDefault method, therefore you don't have to mock it.