no-unnecessary-assertion.md

jest/no-unnecessary-assertion

📝 Disallow unnecessary assertions based on types.

💭 This rule requires type information.

When using TypeScript, runtime assertions based on types can often be omitted provided that the types are accurate.

Rule details

This rule warns when you do an assertion about being null, undefined, or NaN on something that cannot be those types, as that indicates either the assertion can be removed or the types need to be adjusted.

The following patterns are considered warnings:

expect('hello world'.match('sunshine') ?? []).toBeNull();

expect(User.findOrThrow(1)).toBeDefined();

expect(map.getOrInsert('key', 'default')).not.toBeUndefined();

expect(user.name).not.toBeNaN();

The following patterns are not considered warnings:

expect('hello world'.match('sunshine')).toBeNull();

expect(User.findOrNull(1)).toBeDefined();

expect(map.get('key')).not.toBeUndefined();

expect(user.age).not.toBeNaN();