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prefer-presence-queries.md

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Enforce specific queries when checking element is present or not (testing-library/prefer-presence-queries)

The (DOM) Testing Library allows to query DOM elements using different types of queries such as get* and query*. Using get* throws an error in case the element is not found, while query* returns null instead of throwing (or empty array for queryAllBy* ones). These differences are useful in some situations:

  • using getBy* queries when asserting if element is present, so if the element is not found the error thrown will offer better info than asserting with other queries which will not throw an error.
  • using queryBy* queries when asserting if element is not present, so the test doesn't fail immediately when the element is not found and the assertion can be executed properly.

Rule details

This rule fires whenever:

  • queryBy* or queryAllBy* are used to assert element is present with .toBeInTheDocument(), toBeTruthy() or .toBeDefined() matchers or negated matchers from case below.
  • getBy* or getAllBy* are used to assert element is not present with .toBeNull() or .toBeFalsy() matchers or negated matchers from case above.

Examples of incorrect code for this rule:

test('some test', () => {
  render(<App />);

  // check element is present with `queryBy*`
  expect(screen.queryByText('button')).toBeInTheDocument();
  expect(screen.queryAllByText('button')[0]).toBeTruthy();
  expect(screen.queryByText('button')).not.toBeNull();
  expect(screen.queryAllByText('button')[2]).not.toBeNull();
  expect(screen.queryByText('button')).not.toBeFalsy();

  // check element is NOT present with `getBy*`
  expect(screen.getByText('loading')).not.toBeInTheDocument();
  expect(screen.getAllByText('loading')[1]).not.toBeTruthy();
  expect(screen.getByText('loading')).toBeNull();
  expect(screen.getAllByText('loading')[3]).toBeNull();
  expect(screen.getByText('loading')).toBeFalsy();
});

Examples of correct code for this rule:

test('some test', async () => {
  render(<App />);
  // check element is present with `getBy*`
  expect(screen.getByText('button')).toBeInTheDocument();
  expect(screen.getAllByText('button')[9]).toBeTruthy();
  expect(screen.getByText('button')).not.toBeNull();
  expect(screen.getAllByText('button')[7]).not.toBeNull();
  expect(screen.getByText('button')).not.toBeFalsy();

  // check element is NOT present with `queryBy*`
  expect(screen.queryByText('loading')).not.toBeInTheDocument();
  expect(screen.queryAllByText('loading')[8]).not.toBeTruthy();
  expect(screen.queryByText('loading')).toBeNull();
  expect(screen.queryAllByText('loading')[6]).toBeNull();
  expect(screen.queryByText('loading')).toBeFalsy();

  // `findBy*` queries are out of the scope for this rule
  const button = await screen.findByText('submit');
  expect(button).toBeInTheDocument();
});

Further Reading