如何使用 React 测试库测试 React 组件是否返回 null 或其子级？

Question

I have a React component that returns its children to be rendered by React if the prop isTrue is truth-y. If its prop isTrue is false-y, then the component returns null , and React doesn't render anything.

I need to test it as a component, mount it, pass the prop, and test if it's children is getting rendered when the prop isTrue is truth-y, or we are getting null if isTrue is false-y.

Here is my component:

const RenderIf = ({ isTrue, children }) => {
    if (isTrue) {
        return children;
    }
    return null;
}
export default RenderIf

Answer 1

expect(container).toBeEmptyDOMElement()

Answer 2

import React from 'react'; import { render } from '@testing-library/react'; import '@testing-library/jest-dom/extend-expect'; //... describe('TestHistory', () => { it('should render nothing if there are no history entries', () => { // ARRANGE // ACT const { container } = render( <TestHistory version={1} versionHistory={[]} datasetType={DatasetType.VALIDATION} />, ); // ASSERT expect(container).toBeEmptyDOMElement(); }); });

Answer 3

I'd think in this case it is probably ok to test the whole html. react-testing-library wraps your content with a single div so you could something like that:

const { container } = render(<MyComponent ifTrue={false}>Content</MyComponent>);
expect(container.innerHTML).toBe('<div></div>');

If you don't like this approach, you can still render a children with a test-id / text and query it to see if it's present.

Answer 4

expect(container.innerHTML).toEqual('');