Why override `ExecutionContext` for ScalaTest? about cats-effect-testing HOT 4 CLOSED

I'd have to look back, but I imagine the reason it's being overridden is because the reasoning in the paragraph you quoted isn't particularly compelling. :-) In general, the right way to implement this sort of concern is a rate limiting on the number of tests being run, not a rate limiting on the thread pool. The paragraph is essentially making the argument that concurrency is bad, which… I'm not sure I buy.

With that said, the global EC is also usually quite bad, but for other reasons.

With all of that said, your use-case sounds like it really does need to be sequential. I don't know ScalaTest very well; I take it that it has no equivalent to Specs2's sequential scheduling strategy?

from cats-effect-testing.

Hello,
I also had inconsistencies with my test runs with that, i also reverted to the scalatest default EC and it works "normally" with that change.

@djspiewak I agree with you that this is not really logical but i think that's the way scalatest implements async tests.
I would really love to migrate my code to another test framework but for now it will have to do :)

from cats-effect-testing.

From what I could tell ScalaTest's async test setup depends on a synchronous EC, which is how it guarantees tests are run in serial. If you have that you don't need to build any fancy logic for waiting for previous async test results I suppose. I'm guessing this is maybe legacy code from when ScalaTest only had sync testing? I agree it's not a particularly good reason to have a synchronous EC. IMO if your production code is concurrent, your tests should be too (race conditions and all).

ScalaTest says it runs all tests in the same suite sequentially if you don't use ParallelTestExecution but apparently that's not the case when using async tests. In my opinion ScalaTest should have the same behaviour with sync and async tests of waiting for one test to finish before starting another. But that's outside of the scope for this issue and library.

For now I've created my own copy of the AsyncIOSpec which leaves out the EC:

trait AsyncIOSpec extends AssertingSyntax with EffectTestSupport { asyncTestSuite: AsyncTestSuite =>
  implicit val ioContextShift: ContextShift[IO] = IO.contextShift(executionContext)
  implicit val ioTimer: Timer[IO] = IO.timer(executionContext)
}

from cats-effect-testing.

I think this library now uses the ScalaTest EC? Either way this has been explained to me, so I'll close this issue. Thank you for this wonderful library!

from cats-effect-testing.