Fix part of #89: Introduce test dispatchers support in espresso #1623
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This piggybacks off of the solution introduced in #1276 for Robolectric. That PR allows Robolectric tests in app module to share dependencies with production components by creating a test application & telling Robolectric to use it instead of OppiaApplication via a @config annotation. This PR achieves the same thing by using a custom test runner that reads the same annotation and forces Espresso & instrumentation to use the test application instead of the default OppiaApplication. This setup will be easier once #59 is finished since we can specify the application in per-test manifests that both Robolectric & Espresso will respect. Note that while this lets the same test coroutine dispatchers work in both production & test code for Espresso, some additional work was needed to ensure the coroutines behave correctly. In particular, the coroutines use a fake system clock in Robolectric that requires explicit synchronization points in the tests to allow the clock to move forward & properly coordinate execution between background & main thread operations. However, in Espresso, since everything is using a real clock an idling resource is the preferred way to synchronize execution: it allows the background coroutines to operate in real-time much like they would in production, and then notify Espresso when completed. The test dispatchers API is now setup to support both synchronization mechanisms for both Robolectric & Espresso (the idling resource does nothing on Robolectric and the force synchronization effectively does nothing on Espresso). The first test being demonstrated as now stable is SplashActivityTest (as part of downstream work in #1397.
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/cc @MohamedMedhat1998 since you ran into a situation where coordination synchronization in an Espresso test would be helpful. |
vinitamurthi
approved these changes
Aug 12, 2020
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Thanks @vinitamurthi! Do you want to resolve your comment threads or is it fine to check in this PR as-is? |
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Resolved my comments, thanks! |
rt4914
approved these changes
Aug 12, 2020
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Thanks everyone! Going to go ahead and merge this to unblock #1624. |
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Fixes part of #89 by introducing proper support for test coroutine dispatchers in Espresso.
This piggybacks off of the solution introduced in #1276 for Robolectric. That PR allows Robolectric tests in app module to share dependencies with production components by creating a test application & telling Robolectric to use it instead of OppiaApplication via an
@Configannotation.This PR achieves the same thing by using a custom test runner that reads the same annotation and forces Espresso & instrumentation to use the test application instead of the default OppiaApplication. This setup will be easier once #59 is finished since we can specify the application in per-test manifests that both Robolectric & Espresso will respect.
Note that while this lets the same test coroutine dispatchers work in both production & test code for Espresso, some additional work was needed to ensure the coroutines behave correctly. In particular, the coroutines use a fake system clock in Robolectric that requires explicit synchronization points in the tests to allow the clock to move forward & properly coordinate execution between background & main thread operations. However, in Espresso, since everything is using a real clock an idling resource is the preferred way to synchronize execution: it allows the background coroutines to operate in real-time much like they would in production, and then notify Espresso when completed. The test dispatchers API is now setup to support synchronization mechanisms for both Robolectric & Espresso (the idling resource does nothing on Robolectric and the force synchronization effectively does nothing on Espresso).
The first test being demonstrated as now stable on both Robolectric & Espresso is SplashActivityTest (as part of downstream work in #1397).