How can I check if element does not exist in a React test?

I want to test that on initial render of the parent component, there are no child components rendered in the document.

On every press of the button, the parent component generates a child component within it. On init, the child component array is empty. I therefore expect my child componet test-id to be null on initial render, when I render my parent component.

Parent component:

const ParentComponent = () => {

  const [childComponentsArray, setChildComponentsArray] = useState([]);

  const createChildComponent = () => {
    const objToAdd = {
      // Generate uuid for each component
      uuid: uuid()
    };

    setChildComponentsArray([...childComponentsArray, objToAdd]);
  };

  return (
    <div>
      {childComponentsArray.length > 0 && <div>
        {childComponentsArray.map(() => {
          return <div className={'child-item'}>
            <ChildComponent />
          </div>;
        })}
      </div>}

      <ButtonContainer variant={'secondary'} label={'+ ' + component.addLabel}
                       onClick={() => createChildComponent()}
                       />
    </div>
  );
};

Child component:

const ChildComponent = () => {

return (
<div data-testid={'childComponentTestId'}>
<p> I'm in child component! </p>
</div
)
}

Unit test:

test('on render, no child items are visible', () => {

  render(
    <RecoilRoot>
      <ParentComponent />
    </RecoilRoot>
  )

  expect(screen.getByTestId('childComponentTestId')).toBeNull();

});

When executing my test I get the following error in my unit test:

TestingLibraryElementError: Unable to find an element by: [data-testid="childComponentTestId"]

I find this error a bit of a paradox, since that is exactly what I want it to be.

note Passing the data-testid as a prop does not help. Using .not.toBeInDocument() does not work. Using .toBeUndefined() does not work either.

You should use queryByTestId as it returns null if object is not found. See more on the documentation site.

ex: expect(queryByTestId('childComponentTestId')).toBe(null);