How to verify React props in Jest and Enzyme?

You need to find the StyledButton in the Button component before asserting the props

// Button.test.js
import React from 'react';
import { shallow } from 'enzyme';

import Button from '../../components/Button/Button';
import { StyledButton } from './styled'

describe('Component: Button', () => {
  const minProps = {
    text: '',
    size: '',
  };  

  it('renders a button in size of "small" with text in it', () => {
    const wrapper = shallow(
      <Button {...minProps} size="small" text="Join us" />
    );

    expect(wrapper.find(StyledButton).prop('size')).toBe('small');
    expect(wrapper.find(StyledButton).prop('text')).toBe('Join us');
  });
});