Partially fix #89: Introduce test coroutine dispatchers (early testing utility) #927
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test coroutine dispatcher. This includes introducing a test-only module to contain testing dependencies.
BenHenning
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implementation to prepare for code review.
BenHenning
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rt4914
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May 21, 2020
testing/src/main/java/org/oppia/testing/TestCoroutineDispatchers.kt
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vinitamurthi
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May 21, 2020
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Thanks everyone! |
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Introduce a test coroutine dispatcher & coordination utility to guarantee determinism in Robolectric tests. This is not yet app module or Espresso compatible (that requires abstracting the main thread portion & leveraging IdlingResources, plus verifying the replacement mechanism for app module dependencies). #89 is tracking the additional work needed after this PR is submitted.
This also introduces a new testing module where test-only dependencies can live. We shouldn't over-user this yet (e.g. app test deps should stay in the app module), but this is a pattern we will make more use of in the future (especially after we move to Bazel in #59).
This solves one critical requirement for resolving #89: arranging thread execution so that it can be deterministically idled. This was used successfully in downstream tests (see #928). However, please note that this implementation is still incomplete. #89 includes additional details of what work is needed here, so integrations with this utility should be used cautiously until it has had time to be finalized.
This implementation is loosely based on Kotlin's experimental TestCoroutineDispatcher, except the implementation needed significant changes in order to work in this coordinated environment so it was effectively rewritten from the ground up using Kotlin's as a reference for how to actually continue suspended execution.
Finally, no tests were added yet since the implementation still may broadly change and certain aspects aren't trivially testable (like the fake system clock since it's not yet correctly coordinating system time in tests across all aspects of the simulated Android test environment).