Testing suspending function - no tests were found (sometimes)

Issue

I'm having trouble understanding a strange behavior when trying to test my suspending Spring Kotlin @Controller function:

@Controller
class PersonRSocketController(val personRepository: PersonRepository) {
    private val sharedFlow = flow<Person> {
        for (i in 1..1000) {
               emit(Person(i.toLong(), firstName = "$i - firstName", lastName = "$i - lastName"))
        }
    }.buffer(100).shareIn(GlobalScope, SharingStarted.WhileSubscribed(replayExpirationMillis = 0),replay = 0)

    @MessageMapping("currentpersons")
    suspend fun currentPersons(): Flow<Person?> {
        return sharedFlow
    }

} 

Test:

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
class RsocketServerAppTests @Autowired constructor(
    val rSocketRequesterBuilder: RSocketRequester.Builder,
    @LocalServerPort val serverPort: Int
) {
    @Test
    fun testRSocket() = runBlocking{
        val requestSpec =
            rSocketRequesterBuilder.websocket(URI.create("ws://localhost:$serverPort/rsocket")).route("currentpersons")
        var result = requestSpec.retrieveFlow<PersonDataRequest>()
        assertThat(result.first().firstName).isEqualTo("1 - firstName")
//      for (i in 1..2) {
//
//      }
    }

}

When I run the test the test is not run - Maven reports that no tests were found. When I uncomment the for-loop the test will run and pass. when I replace the for-loop with a println("") the test will also run and pass. When I replace it with assertThat(1).isEqualTo(1) the test will not run. Can somebody explain this?

Solution

The test is not discovered by JUnit whenever its return type is not void. See JUnit test methods can't return a value. I think this is quite unfortunate for the issue I came across.

Answered By - Hans Wurst