Read React state in Jest test

JestReadReactState.test.tsx

import React from 'react';
import TestRenderer from 'react-test-renderer';
import CognitoLogin from './CognitoLogin';
import _ from 'lodash';

it('When no `code` or `email` `onSavePress` should set `message` to `Need code and user e-mail`', async (done) => {
  // Arrange
  const wrapper = TestRenderer.create(<CognitoLogin />);
  const child = wrapper.root.findByProps({
    testID: 'ForgotForm',
  });
  // Act
  await child.props.onSubmit();
  // Assert
  const result = _.get(wrapper, ['root', 'instance', 'state', 'message']);
  expect(result).toBe('Please enter username');
  done();
});