isEmptyRender does not work as expected on memo'd FCs

[wezleytsai]

Current behavior

wrapper.isEmptyRender() returns true for a component that returns null. However, if the component is memoized, wrapper.isEmptyRender() returns false.

Expected behavior

Memoized or not, wrapper.isEmptyRender() to return true when component returns null.

Your environment

See reproducible: https://codesandbox.io/s/goofy-worker-zzing

API

• shallow
• mount
• render

Version

library	version
enzyme	3.11.0
react	16.13.1
react-dom	16.13.1
react-test-renderer
adapter (below)	1.15.2

Adapter

• enzyme-adapter-react-16
• enzyme-adapter-react-16.3
• enzyme-adapter-react-16.2
• enzyme-adapter-react-16.1
• enzyme-adapter-react-15
• enzyme-adapter-react-15.4
• enzyme-adapter-react-14
• enzyme-adapter-react-13
• enzyme-adapter-react-helper
• others ( )

[9oelM]

I believe I am experiencing a similar issue.
Almost exactly same as your codesandbox code:

const Component = React.memo(() => null)
const wrapper = mount(<Component />)
expect(wrapper.isEmptyRender()).toBe(true)

It will return false. As a workaround, I used expect(wrapper.html()).toBe(``)