Support for beforeEach/afterEach in fast-check/jest

[hsommerlandreason]

🚀 Feature Request

I am having issues using sinon to mock things when running fast-check with jest, one cannot re-mock something with sinon that has already been mocked.
So after each test the mocks have to be restored, this can be done via either the afterEach hook for a specific property test or with the global hooks when not using fast-check/jest.

But when using fast-check/jest these hooks are not available (at least not what i could find) and the global hooks don't seem to be applied. The beforeEach/afterEach hooks provided by jest does not work as they are not executed on every single check which they need to be.

This also applies for the cleanup method from @testing-library/react which will also need to be executed after every test.

Motivation

This would be very appreciated as the omission of this feature from fast-check/jest makes testing several things a lot more complicated and annoying requiring either manually calling the cleanup stuff or constructing workarounds.

Example

Here is a bit of a contrived example.

const whatever = {
 bob: (n: number) => n - 10
}

test.prop([fc.nat()])('failing', (n) => {
 sinon.replace(whatever, 'bob', sinon.fake.returns(n))
 expect(whatever.bob(n)).toEqual(n)
 // sinon.restore()  /* if this is called here the tests will work.
})

test('works', () => {
 fc.assert(fc.property(fc.nat(), (n) => {
   sinon.replace(whatever, 'bob', sinon.fake.returns(n))
   expect(whatever.bob(n)).toEqual(n)
   }).afterEach(() => sinon.restore())
 )
})

This will fail with:

 Property failed after 2 tests
   { seed: 1576879931, path: "1:0", endOnFailure: true }
   Counterexample: [0]
   Shrunk 1 time(s)
   Got TypeError: Attempted to replace bob which is already replaced

[dubzzz]

Definitely something worth adding. It would require te have a way to either hook into the beforeEach defined for Jest or expose one via fast-check and fill the one of Jest with it.

[dmurvihill]

+1 for this, I'm trying to use with jest-mock-axios and having trouble resetting the mock between tests.

[dubzzz]

For now, you can use https://fast-check.dev/docs/configuration/global-settings/#shared-settings with beforeEach or beforeEachAsync

[ej-shafran]

Hey - any updates on this? If needed, I can try implementing this and open a pull request if I manage to...

[dubzzz]

@ej-shafran I have not worked on this issue recently. You can give it a try if you want