Skip to content

Latest commit

 

History

History
57 lines (39 loc) · 2.4 KB

prefer-implicit-assert.md

File metadata and controls

57 lines (39 loc) · 2.4 KB

Suggest using implicit assertions for getBy* & findBy* queries (testing-library/prefer-implicit-assert)

Testing Library getBy* & findBy* queries throw an error if the element is not found. Therefore it is not necessary to also assert existence with things like expect(getBy*.toBeInTheDocument() or expect(await findBy*).not.toBeNull()

Rule Details

This rule aims to reduce unnecessary assertion's for presence of an element, when using queries that implicitly fail when said element is not found.

Examples of incorrect code for this rule with the default configuration:

// wrapping the getBy or findBy queries within a `expect` and using existence matchers for
// making the assertion is not necessary
expect(getByText('foo')).toBeInTheDocument();
expect(await findByText('foo')).toBeInTheDocument();

expect(getByText('foo')).toBeDefined();
expect(await findByText('foo')).toBeDefined();

const utils = render(<Component />);
expect(utils.getByText('foo')).toBeInTheDocument();
expect(await utils.findByText('foo')).toBeInTheDocument();

expect(await findByText('foo')).not.toBeNull();
expect(await findByText('foo')).not.toBeUndefined();

Examples of correct code for this rule with the default configuration:

getByText('foo');
await findByText('foo');

const utils = render(<Component />);
utils.getByText('foo');
await utils.findByText('foo');

// When using queryBy* queries these do not implicitly fail therefore you should explicitly check if your elements exist or not
expect(queryByText('foo')).toBeInTheDocument();
expect(queryByText('foo')).not.toBeInTheDocument();

When Not To Use It

If you prefer to use getBy* & findBy* queries with explicitly asserting existence of elements, then this rule is not recommended. Instead check out this rule prefer-explicit-assert

  • Never use both prefer-implicit-assert & prefer-explicit-assert choose one.
  • This library recommends prefer-explicit-assert to make it more clear to readers that it is not just a query without an assertion, but that it is checking for existence of an element

Further Reading