no-useless-matcher-to-be-null.md

Disallow using .toBeNull() when TypeScript types conflict with it (proper-tests/no-useless-matcher-to-be-null)

💼 This rule is enabled in the following configs: ☑️ flat/recommended, ✅ recommended.

Rule details

This rule disallows using not.toBeNull() matcher when it is known that variable is always not null.

The following patterns are considered errors:

const fooWithType: string = 'foo';
expect(foo).not.toBeNull();

const foo = 'foo';
expect(foo).not.toBeNull();

const user = repository.findByIdOrThrow(123); // return type is `User`
expect(user).not.toBeNull();

You should remove these expectations because they are redundant.