valid-expect-with-promise.md

jest/valid-expect-with-promise

📝 Require that resolve and reject modifiers are present (and only) for promise-like types.

💭 This rule requires type information.

When working with promises, you must remember to use resolves and rejects to assert on the value returned (or thrown) by the promise, rather than the promise itself.

Inversely, while Jest does not prevent you from using resolves and rejects on non-promise values, it is not necessary.

When TypeScript is in use, it is possible to determine when resolves and rejects should and should not be needed.

Rule details

This rule warns when:

• an expect is given a promise-like value but without resolves or rejects
• an expect is not given a promise-like value, but is used with resolves or rejects

The following patterns are considered warnings:

expect('hello world').resolves.toBe('hello sunshine');

expect(new Promise(r => r(0))).toThrow('oh noes!');

The following patterns are not considered warnings:

expect('hello world').toBe('hello sunshine');

expect(new Promise(r => r(0))).rejects.toThrow('oh noes!');