Unit testing coroutines runBlockingTest: This job has not completed yet

Question

Please find below a function using a coroutine to replace callback :

override suspend fun signUp(authentication: Authentication): AuthenticationError {     return suspendCancellableCoroutine {         auth.createUserWithEmailAndPassword(authentication.email, authentication.password)             .addOnCompleteListener(activityLifeCycleService.getActivity()) { task ->                 if (task.isSuccessful) {                     it.resume(AuthenticationError.SignUpSuccess)                 } else {                     Log.w(this.javaClass.name, "createUserWithEmail:failure", task.exception)                     it.resume(AuthenticationError.SignUpFail)                 }             }     } } 

Now I would like to unit testing this function. I am using Mockk :

  @Test   fun `signup() must be delegated to createUserWithEmailAndPassword()`() = runBlockingTest {        val listener = slot<OnCompleteListener<AuthResult>>()       val authentication = mockk<Authentication> {         every { email } returns "email"         every { password } returns "pswd"       }       val task = mockk<Task<AuthResult>> {         every { isSuccessful } returns true       }        every { auth.createUserWithEmailAndPassword("email", "pswd") } returns           mockk {             every { addOnCompleteListener(activity, capture(listener)) } returns mockk()           }      service.signUp(authentication)        listener.captured.onComplete(task)     } 

Unfortunately this test failed due to the following exception : java.lang.IllegalStateException: This job has not completed yet

I tried to replace runBlockingTest with runBlocking but the test seems to wait in an infinite loop.

Can someone help me with this UT please?

Thanks in advance

Answer 1

As can be seen in this post:

This exception usually means that some coroutines from your tests were scheduled outside the test scope (more specifically the test dispatcher).

Instead of performing this:

private val networkContext: CoroutineContext = TestCoroutineDispatcher()  private val sut = Foo(   networkContext,   someInteractor )  fun `some test`() = runBlockingTest() {   // given   ...    // when   sut.foo()    // then   ... } 

Create a test scope passing test dispatcher:

private val testDispatcher = TestCoroutineDispatcher() private val testScope = TestCoroutineScope(testDispatcher) private val networkContext: CoroutineContext = testDispatcher  private val sut = Foo(   networkContext,   someInteractor ) 

Then in test perform testScope.runBlockingTest

fun `some test`() = testScope.runBlockingTest {   ... }  

See also Craig Russell's "Unit Testing Coroutine Suspend Functions using TestCoroutineDispatcher"