defaultProps for shallow renders do not work with React.memo

[KamalAman]

Current behavior

Default props from the "inner component" are not applied to memo'd component. The second test fails with <div>NaN</div>

import React from 'react';
import { shallow } from 'enzyme';

const Add = ({ a, b }) => <div>{a + b}</div>;

Add.defaultProps = {
  a: 2,
  b: 3,
};

const MemoAdd = React.memo(Add);

describe('Enzyme Shallow Default Props Test', () => {
  it('default props should be applied to components', () => {
    const wrapper = shallow(<Add />);
    expect(wrapper.html()).toEqual('<div>5</div>');
  });

  it('default props should be applied to memo components', () => {
    const wrapper = shallow(<MemoAdd />);
    expect(wrapper.html()).toEqual('<div>5</div>');
  });
});

Expected behavior

Default props should be applied to the memo component

Your environment

API

• shallow
• mount
• render

Version

library	version
enzyme	3.9.0
react	16.8.6
react-dom	16.8.6
react-test-renderer	16.8.6
adapter (below)

Adapter

• enzyme-adapter-react-16
• others ( )

[ljharb]

Note that using .html() invokes render - prefer .debug(). However, this still seems to fail with debug, so thanks, it's a bug :-)

[ljharb]

This actually seems like a bug in the shallow renderer with memoized components. I've filed facebook/react#15556 to track it.