How do you test for the non-existence of an element using jest and react-testing-library?

问题

I have a component library that I'm writing unit tests for using Jest and react-testing-library. Based on certain props or events I want to verify that certain elements aren't being rendered.

getByText, getByTestId, etc throw and error in react-testing-library if the element isn't found causing the test to fail before the expect function fires.

How do you test for something not existing in jest using react-testing-library?

回答1:

From DOM Testing-library Docs - Appearance and Disappearance

Asserting elements are not present

The standard getBy methods throw an error when they can't find an element, so if you want to make an assertion that an element is not present in the DOM, you can use queryBy APIs instead:
const submitButton = screen.queryByText('submit')
expect(submitButton).toBeNull() // it doesn't exist
The queryAll APIs version return an array of matching nodes. The length of the array can be useful for assertions after elements are added or removed from the DOM.
const submitButtons = screen.queryAllByText('submit')
expect(submitButtons).toHaveLength(2) // expect 2 elements
not.toBeInTheDocument

The jest-dom utility library provides the .toBeInTheDocument() matcher, which can be used to assert that an element is in the body of the document, or not. This can be more meaningful than asserting a query result is null.
import '@testing-library/jest-dom/extend-expect'
// use `queryBy` to avoid throwing an error with `getBy`
const submitButton = screen.queryByText('submit')
expect(submitButton).not.toBeInTheDocument()

回答2:

Use queryBy / queryAllBy.

As you say, getBy* and getAllBy* throw an error if nothing is found.

However, the equivalent methods queryBy* and queryAllBy* instead return null or []:

queryBy

queryBy* queries return the first matching node for a query, and return null if no elements match. This is useful for asserting an element that is not present. This throws if more than one match is found (use queryAllBy instead).

queryAllBy queryAllBy* queries return an array of all matching nodes for a query, and return an empty array ([]) if no elements match.

https://testing-library.com/docs/dom-testing-library/api-queries#queryby

So for the specific two you mentioned, you'd instead use queryByText and queryByTestId, but these work for all queries, not just those two.

回答3:

You have to use queryByTestId instead of getByTestId.

Here a code example where i want to test if the component with "car" id isn't existing.

 describe('And there is no car', () => {
  it('Should not display car mark', () => {
    const props = {
      ...defaultProps,
      base: null,
    }
    const { queryByTestId } = render(
      <IntlProvider locale="fr" messages={fr}>
        <CarContainer{...props} />
      </IntlProvider>,
    );
    expect(queryByTestId(/car/)).toBeNull();
  });
});

回答4:

getBy* throws an error when not finding an elements, so you can check for that

expect(() => getByText('your text')).toThrow('Unable to find an element');

回答5:

You can use react-native-testing-library "getAllByType" and then check to see if the component is null. Has the advantage of not having to set TestID, also should work with third party components

 it('should contain Customer component', () => {
    const component = render(<Details/>);
    const customerComponent = component.getAllByType(Customer);
    expect(customerComponent).not.toBeNull();
  });

来源：https://stackoverflow.com/questions/52783144/how-do-you-test-for-the-non-existence-of-an-element-using-jest-and-react-testing

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