expect.anything() fails on null value

[koko236]

Hi,

I have following test:

import { describe, it, expect } from 'vitest';

describe('expect.anything() matcher', () => {
  it('should allow null values', () => {
    const obj = {
      id: 1,
      sort: null,
      title: 'Where',
      description: 'description'
    };

    expect(obj).toEqual(expect.objectContaining({
      id: expect.any(Number),
      sort: expect.anything(),
      title: expect.any(String),
      description: expect.any(String)
    }));
  });
});

It fails because of sort: null line however documentation (and chat GPT) claim that expect.anything() should allow any value including null or undefined and it's useful for testing of existence of the key. Any suggestions why that happens and how to write a passing test allowing null here?

[sheremet-va]

The documentation is wrong, expect.anything expects the value not to just be defined, but also not to be null or undefined. If you don't care for the value, just omit it - you already use objectContaining. If you know it's null, use null.

[koko236]

Thanks for clarification, is there an idiomatic way to test for optional values of some type?

[sheremet-va]

I think there is now expect.toBeOneOf([null, 'another value'])

[koko236]

Yes, that works! Thanks a lot for the tip.