Ktor / Kodein - How to write Integration Tests

Question

Currently I write a small demo-app which uses Ktor as its Application Environment and Kodein as the Dependency Injection Framework.

During the initialization of the Application I do import some modules, one of those I would like to replace during the initialization of the Integration Tests:

fun Application.module(testing: Boolean = false) {
logger.debug { "Starting main" }

restModule()

di {
  bind<Json>() with singleton {
    Json {
      ...
    }
  }

  import(persistenceModule)
}

In the test, I would like to use a different persistenceModule, say eg. a MemoryModule. My tests are initialized like:

fun start() {
  val configPath = ClassLoader.getSystemResource("application-acceptanceTest.conf").file
  engine = embeddedServer(CIO, commandLineEnvironment(arrayOf("-config=$configPath")))
  engine.start()

  val disposable = engine.environment.monitor.subscribe(ApplicationStarted) { application: Application ->
    started = true
  }

  while (!started) {
    Thread.sleep(10)
  }
  disposable.dispose()
}

I have tried already to call

engine.application.di

but this gives me (quite obviously) only access to the Ktor Feature, which is already initialized. Is anything like this possible at all?

In the definition of `Application.module`, you can access the property `developmentMode` and if it's `true`, then import the memory module instead of the persistent one. You can find information about enabling development mode here https://ktor.io/docs/development-mode.html#enable — Aleksei Tirman, Mar 25 '21 at 15:30

score 1 · Accepted Answer · answered Mar 26 '21 at 05:45

Kodein-DI allows you to override dependencies. Regarding the following interface:

interface Repository {
    fun save()
    fun find()
}

You can have a production implementation, included in its own DI module:

class PersistenceRepository : Repository {
    /* implementation */
}

val persistenceModule = DI.Module("persistenceModule") {
    bind<Repository>() with singleton { PersistenceRepository() }
}

and also a test implementation of that same interface:

class MemoryRepository : Repository {
    /* implementation */
}

val memoryModule = DI.Module("memoryModule") {
    bind<Repository>(overrides = true) with singleton { MemoryRepository() }
}

Note the overrides parameter that needs to be explicit.

You can pass a DI container to your Ktor function:

val mainDI = DI {
    import(persistenceModule)
}

fun Application.main(di: DI) {
    di { extend(di) }
}

And extend the mainDI in your tests, to override the proper bindings with the memoryModule:

class ApplicationTest {
    val testDI = DI {
        extend(mainDI)
        import(memoryModule, allowOverride = true)
    }
    
    @Test
    fun myTest() {
        withTestApplication({ main(testDI) })
        // ...
    }
}

Ktor / Kodein - How to write Integration Tests

1 Answers1