feature: implement `toBeEmptyElement` Jest matcher

[mdjastrzebski]

Describe the Feature

toBeEmptyDOMElement is a Jest DOM matcher that asserts the visibility of given element by inspecting whether it contains any child elements.

Adapting it to our case it would assert that given host element does not contain any host children elements. It might contain some composite elements as long as these do not have host descendants. We already have function for getting host children of given element (getHostChildren) so that should be relatively straightforward.

Possible Implementations

Proposed API:

export function toBeEmptyElement(
  this: jest.MatcherContext,
  element: ReactTestInstance
)

The matcher should:

1. Validate that it is invoked on a host element
2. Check if given element contains any host child elements (using getHostChildren fn)

Each matcher should have a fairly comprehensive test suite.

Links

• toBeEmptyDOMElement matcher code from Jest DOM: https://github.com/testing-library/jest-dom/blob/main/src/to-be-empty-dom-element.js
• toBeEmptyElement implementation for Jest Native: https://github.com/testing-library/jest-native/blob/main/src/to-be-empty-element.ts

Related Issues

#1454

[kyawthura-gg]

Hi @mdjastrzebski, I would like to work on this issue. Thanks

[mdjastrzebski]

@kyawthura-gg Go ahead! Pls submit PR when you're ready.

[mdjastrzebski]

🎉 Release in version: v12.4.0