I want to create a library with a custom time-base...

# coroutines

[flosch]

I want to create a library with a custom time-based operator extension on Flow, such as for example Flow<T>.throttleFirst() here. @elizarov wrote that to test such an operator we would have to use the DelayController if available instead of System.currentTimeMills() , which of course makes total sense. My question: How could I publish this library without having kotlinx-coroutines-test in the release dependencies? Meaning how would I prevent the user of my library having kotlinx-coroutines-test in their release binaries when they use my dependency?

[louiscad]

You can just use TimeSource.Monotonic and delay (experimental time API). Then, if users use delay controlling dispatcher, it will just work, without you having to do anything special.

[flosch]

Thanks! That would mean I would require the library user to use an experimental api, which is fine for my use-case. But is there a way that this could be implemented without this experimental API and not publishing it with test dependencies in release?

[louiscad]

@flosch Yes, you can use System.nanoTime() yourself (on JVM/ART, other platforms have different APIs), and count milliseconds after converting from nanos, or count it all in nanoseconds.

[flosch]

Sure, yes, that is what I am currently doing! However this does not let me use the DelayController , when testing my custom operator. Or am I missing something?

[louiscad]

You can use delay which is controlled by DelayController in test conditions.

[louiscad]

Having a library control the DelayController from under would be surprising to the consumer projects and might break other parts of the test(s).

[flosch]

Ahh okay, yea that actually makes sense! Thank you very much