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androidkotlinjunitkotlin-coroutines

TestCoroutineScheduler() not initialising while using UnconfinedTestDispatcher() for MainCoroutineRule

After updating coroutinesKotlinVersion to 1.7.1 , facing these issues while creating MainCoroutineRule with UnconfinedTestDispatcher()

Could not initialize class kotlinx.coroutines.test.TestCoroutineScheduler
java.lang.NoClassDefFoundError: Could not initialize class kotlinx.coroutines.test.TestCoroutineScheduler
    at kotlinx.coroutines.test.TestCoroutineDispatchersKt.UnconfinedTestDispatcher(TestCoroutineDispatchers.kt:87)
    at kotlinx.coroutines.test.TestCoroutineDispatchersKt.UnconfinedTestDispatcher$default(TestCoroutineDispatchers.kt:83)
    at net.example.cellfish.MainCoroutineRule.<init>(MainCoroutineRule.kt:12)
    at net.example.cellfish.search.viewmodel.SearchTransactionHistoryViewModelTest.<init>(SearchTransactionHistoryViewModelTest.kt:49)

If I downgrade the version to 1.6.4, test cases seems to be working fine. Able to initlise MainCoroutineRule.

For Ref-

@OptIn(ExperimentalCoroutinesApi::class)
class MainCoroutineRule constructor(
    val testDispatcher: TestDispatcher = UnconfinedTestDispatcher()
) : TestWatcher() {

    override fun starting(description: Description) {
        super.starting(description)
        Dispatchers.setMain(testDispatcher)
    }

    override fun finished(description: Description) {
        super.finished(description)
        Dispatchers.resetMain()
    }
}

Dependencies for kotlin coroutine

implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.1"
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.1"
testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:1.7.1"
Solution

  • So figured out that internally kotlinx-coroutines-test:1.7.1 is trying to use kotlin-stdlib:1.8.10. But coz of our usecase we were forcing any kotlin based library to use 1.7.20 and so making kotlinx-coroutines-test:1.7.1 to use kotlin-stdlib:1.7.20 as well . It it seems like its some compatibility issue (backward compatibility) with kotlinx-coroutines-test:1.7.1 for old kotlin version.