sum.js

class App extends Component {
    render() {
        return (
            <div>
                <Sum/>
                <Multiply/>
            </div>
        );
    }
}

test('display Sum and Multiply components', () => {
    const component = mount(<App/>);
    expect(component.find(Sum).length).toEqual(1);
    expect(component.find(Multiply).length).toEqual(1);
});