ZIO Mock support for impure methods, ZStream and ZSink #3247
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Updated |
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As soon as CI finishes this is ready to be reviewed & merged @adamgfraser . |
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@adamgfraser can we rerun https://app.circleci.com/pipelines/github/zio/zio/6519/workflows/3cf22b04-08a3-4c31-9752-bb78704e3270/jobs/67033 ? |
| ## Creating a mock service | ||
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| We'll be assuming you've read [How to use modules and layers][doc-use-modules-and-layers] guide. In the main sources we define the _service_, a module alias and _capability accessors_. In test sources we're defining the _mock object_ which will hold _capability tags_ and mock layer machinery. | ||
| We'll be assuming you've read [How to use modules and layers][doc-use-modules-and-layers] guide. In the main sources we define the _service_, a module alias and _capability accessors_. In test sources we're defining the _mock object_ which extends `zio.test.mock.Mock` which holds _capability tags_ and _compose layer_. |
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Great that we have a clear separation between source and test now!
| def overloaded(arg1: Long) = invoke(Overloaded._1, arg1) | ||
| val compose: URLayer[Has[Proxy], Example] = | ||
| ZLayer.fromServiceM { proxy => | ||
| withRuntime.map { rts => |
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Maybe say something about what this is so people don't just think they can do ZIO.runtime[R]?
| def overloaded(arg1: Int) = proxy(Overloaded._0, arg1) | ||
| def overloaded(arg1: Long) = proxy(Overloaded._1, arg1) | ||
| def function(arg1: Int) = rts.unsafeRunTask(proxy(Function, arg1)) | ||
| def sink(a: Int) = rts.unsafeRun(proxy(Sink, a).catchAll(error => UIO(ZSink.fail(error)))) |
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Why do we need to unsafely run a sink or a stream?
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The internal mock machinery returns an IO[E, A] where A <: ZStream or A <: ZSink.
For ZStream E = Nothing, becouse any errors happening in creation of the stream are deferred to the first take (moved into streams error channel ZStream[_, E, _]). For ZSink any errors happening upon creation are caught immidietly resulting in a failed Sink, so we need to manually move the error from our internal mock IO[E, _] to a failed ZSink.
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Could we do something like io.foldCauseM(e => ZStream.fail(e), stream)? Maybe I'm not understanding.
| - `E` is the type of error it can fail with | ||
| - `A` is the type of return value it can produce | ||
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| The `Capability` type is not publicly available, instead you have to extend `Mock` dependent types `Effect`, `Method`, `Sink` or `Stream`. |
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Any other types we want to support mocking? ZManaged? ZSTM? Any way to abstract over this?
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Yes, we should have all ZIO data types covered. I don't see a clean way to abstract over this ATM, but will definately think about it in future.
| */ | ||
| abstract class Method[R <: Has[_]: Tagged, I: Tagged, E: Tagged, A: Tagged](val compose: URLayer[Has[Proxy], R]) | ||
| extends Method.Base[R] { self => | ||
| protected[mock] abstract class Capability[R <: Has[_]: Tagged, I: Tagged, E: Tagged, A: Tagged](val mock: Mock[R]) |
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Can we add variance here or no because of the tags?
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We can't. Variance will break things.
| /** | ||
| * A `Mock[R]` represents a mockable environenment `R`. | ||
| */ | ||
| abstract class Mock[R <: Has[_]: Tagged] { self => |
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It would probably break things, but have not tested. I don't think it would bring any value though, at least in current implementation.
Fixes #2734
This PR introduces support for ZStream/ZSink and non-ZIO methods (regular functions/vals) as well as many refactorings/renames as the additional use cases crystalized the design to be more clean.
To be completed it still needs:
@mockablemacro@accessiblemacroadd test coverage for more advanced use cases composing Streams with Effectsadd more advanced examples of mocks composing Streams with Effects@adamgfraser @jdegoes Once these are completed I'd say ZIO Mock is
1.0ready. I'll try to complete these as soon as possible. Opening the PR earlier so you can track progress and review the approach.Out of the scope of this PR is support for polymorphic ZStreams/ZSinks. It will be tricky to get right, so I'll tackle it seperately and would not like it to be a blocker for this PR.