Why does shallow Rendering not work as expected?

I have the same problem. It solved by using the below .

I have created a jest.config.js file at the root level and add below code.

module.export ={
  setupFiles:[ '<rootDir>/src/setUpTests.js']
 }

I have created setUpTests.js file and add below code.

import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

And solved my problem.