React enzyme testing, Cannot read property ‘have’ of undefined

Use Link instead of <Link />:

describe('<OffCanvasMenu />', () => {
  it('contains 5 <Link /> components', () => {
    const wrapper = shallow(<OffCanvasMenu />);
    expect(wrapper.find(Link)).to.have.length(5);
  });
});

It appears in the 1st example in the airbnb/enzyme docs:

it('should render three <Foo /> components', () => {
  const wrapper = shallow(<MyComponent />);
  expect(wrapper.find(Foo)).to.have.length(3);
});

The syntax .to.have.length is for the Chai Assertion Library. For Jest use .toHaveLength:

it('should render three <Foo /> components', () => {
  const wrapper = shallow(<MyComponent />);
  expect(wrapper.find(Foo)).toHaveLength(3);
});