Mock verification

[nrxus]

faux should support verification that a mock got called with certain arguments.

cc: @muscovite

[giomf]

Are there any plans in the near future for this feature?

[nrxus]

"near future" is overstating it but I definitely want to add this sooner rather than later. I actually did a proof of concept for this on some branch a while ago so it's very doable, I think I just got a little stuck in the UX for it and then stuff came up so I forgot about it and got stale. So hopefully in the near-ish future, but it largely depends on whether I get time/motivation for it or if someone puts a PR up for it.

[BogdanKosarev]

@nrxus hi!
Is there some branch which is a good start point for delving in implementation of verification feature?

[nrxus]

@BogdanKosarev I started working on it here a while ago: https://github.com/nrxus/faux/tree/mock-expectations

but it's fairly stale so no promises that it is easy to pick back up 😅

[DGolubets]

Hi @nrxus,

do you have any plans to pick this up?

Or maybe @BogdanKosarev made progress?

Verifying that a method was not called is very important for some tests.
It could also help with argument checks when mock error is lost.
E.g. Kameo actors can catch and recover from panics, but that also makes them suppress mock errors.

I think that expect! could ideally replace when! (is there any downside to always setting both stubs and verifications?)

[nrxus]

@DGolubets I've been pretty lazy on adding this feature, but it is something I actively want to do and/or am open to someone opening a PR for it.

I generally find mock verification to be a bit of a smell as ideally tests shouldn't be reliant on side-effects of an internal call but I know it is sometimes necessary. I find your use case about actors recovering from panics causing suppression of mock errors pretty interesting, I wonder if there is something else that could be done in that scenario but I'd have to chew on that for a bit 🤔

I wouldn't want expect! (or verify!, or whatever), to replace when! because I do strongly feel that relying on mock expectations is an anti-pattern so I'd want when! to be the default and only reach for expect! on very few cases.