Why do tests with no asserts or expects pass?

[designermonkey]

I've been doing unit testing for years in PHP and Java and if you define a test in those languages without asserting that something happened, the test fails. This is what I thought all unit testing frameworks did. Then I come to vitest.

Can someone explain to me why, if I have a test in my file with nothing in it, it passes?

import { test } from 'vitest'

test('surely this should fail?', () => {

})

[sheremet-va]

The test fails only if the function throws an error. An empty function doesn't throw an error. With this approach you can use any assertion library you like, or just throw an error manually if needed.

[designermonkey]

TDD challenges us to follow the principle of fail, pass, refactor, but we can't do that if we are presented with pass, pass, refactor.

[sheremet-va]

As I said, the framework (Vitest) cannot track assertions because you can use anything as an assertion. We provide expect.hasAssertions() API that you can call if you only use expect.

[nmay231]

@sheremet-va Then can we enable a flag that applies expect.hasAssertions() for all tests, if you only use expect?

If we need to add an opt-out, we could use expect.assertions(0) or expect.assertions("unknown") if we don't know how many assertions there could be.

[sheremet-va]

I guess we can add an option for this. For now, you can call it inside beforeEach for the same effect

[sheremet-va]

Should be addressed in #5729