Hi, I struggle with some testing for Koin in combi...

# koin

[dbaelz]

Hi, I struggle with some testing for Koin in combination with Ktor 3 server. Is it possible to write JVM Unit Tests for Ktor Server with koin-ktor and replace the injected dependencies? My current understanding:
• The normal unit test way for Koin is to call startKoin in the test and then inject different (mock) implementations
• With koin-ktor the Koin plugin handles the start of Koin inside the Ktor server internally. So there's no need to call startKoin in the Unit Test
I tried to use loadKoinModules() , but that didn't work. See minimal code example in the thread. Is it possible to test that way? Is there another approach to do that?

[dbaelz]

My example with Koin Ktor and testing a Ktor Server. It always cals the "real" production implementation instead of the mock provided by mockk.

class MinimalTest {
    private val experienceRepository = mockk<ExperienceRepository>()

    private val koinTestModule = module {
        single<ExperienceRepository> { experienceRepository }
    }

    @Test
    fun minimalTest() = testApplication {
        val experience = listOf(
            Experience(0, LocalDateTime.now(), 1, "reason1"),
            Experience(1, LocalDateTime.now(), 2, "reason2")
        )
        coEvery { experienceRepository.getExperience() } returns experience

        application {
            // The module extension function calls install(Koin) and
            // also injects the ExperienceRepository
            module()

            // Use the mocked ExperienceRepository instead
            loadKoinModules(koinTestModule)
        }

        // Internally the Ktor Server use the routing plugin and
        // then access the data with the ExperienceRepository.
        // It should use the mocked ExperienceRepository, but uses the production one
        val response = client.get(EXPERIENCE.fullResourcePath)
        val actual = Json.decodeFromString(ExperienceDTO.serializer(), response.bodyAsText())
        assert(actual.entries.isNotEmpty())
    }
}

[Dmytro Koval]

Were you able to figure it out?

[dbaelz]

I've realized that it couldn't work because I already injected the repo in the Application.module() function and therefore loadKoinModules provides the mock, but it's never used.

Due Koin issues I can't inject in Route extension function where I needed the repository provided with Koin. Therefore, I did hand over the modules as parameter ListModule in Application.module(). For production only the product module(s), for testing production + the koinTestModule that overrides the repo with the mockk. That works because when handing over multiple modules in Koin existing definitions of one module can be overridden by another.