text: import React from 'react';
  import { configure, shallow } from 'enzyme';
  import Adapter from 'enzyme-adapter-react-16';
  import Books from './Books';
  import Book from './Book';
  import Card from '@material-ui/core/Card'
  
  configure({adapter: new Adapter()});
  
  describe('<Books />', () => {
      let wrapper;
  
      beforeEach(() => {
          wrapper = shallow(<Books />);
      });
  
      it('should render <Book /> elements', () => {
          expect(wrapper.find(Book));
      });
  
      it('should render no card if <Book /> elements value is null', () => {
          let bookWrapper = shallow(<Book />);
          bookWrapper.setProps({book: null});
          expect(bookWrapper.find(Card)).toHaveLength(0);
      });
  
      it('should not contain class `.cardlink` if book data not available', () => {
          let bookWrapper = shallow(<Book />);
          bookWrapper.setProps({book: null});
          expect(wrapper.find('.cardlink')).toHaveLength(0);
        });
  
  });