Button.test.js functionality test

Button.test.js

import React from 'react';
import { Platform, Text, TouchableHighlight, StyleSheet } from 'react-native';
import { shallow } from 'enzyme';
import Button from './Button';

const text = 'test button';

const styles = StyleSheet.create({
  button: {
    height: 20,
  },
  buttonText: {
    color: '#04f',
    fontSize: 16,
  }
});

describe('Button component', () => {
  it('receives props', () => {
    const mockFunc = jest.fn();
    const tree = shallow(
      <Button text={text} onClick={mockFunc} style={styles.button} textStyle={styles.buttonText} />
    );
    const content = shallow(
      <TouchableHighlight onPress={mockFunc} style={styles.button} >
        <Text style={styles.buttonText}>{text}</Text>
      </TouchableHighlight>
    );

    expect(tree.html()).toEqual(content.html());
  });

  it('trigger onClick callback', () => {
    const mockFunc = jest.fn();
    const tree = shallow(
      <Button text={text} onClick={mockFunc} style={styles.button} textStyle={styles.buttonText} />
    );
    const btn = tree.find(TouchableHighlight);
    btn.simulate('press'); // simulate native "press" event 
    expect(mockFunc.mock.calls.length).toEqual(1);
    expect(mockFunc).toBeCalled();
  });
});