Koin 3.1.0 has breaking changes to checkModules syntax and behavior

[russhwolf]

The following is a valid test on both JVM and Native in Koin version 3.0.2 using the koin-core and koin-test modules.

class Box(val value: String)

class KoinModulesTest {
    @Test
    fun checkModulesTest() {
        val koinApplication = startKoin {
            modules(module {
                single { Box(get()) }
            })
        }

        koinApplication.checkModules {
            create<Box> { parametersOf("foo") }
        }
    }

    @AfterTest
    fun tearDown() {
        stopKoin()
    }
}

In Koin 3.1.0, the checkModules() extension function which takes a lambda has been removed, breaking compatibility with existing code. What follows is my attempts to understand the new API.

---

One can try to migrate the checkModules() call like so:

koinApplication.checkModules(defaultValues = mapOf(String::class to "foo"))

This fails with the following message:

org.koin.core.error.BrokenDefinitionException: Definition is broken: [Singleton:'Box'] 
- due to error: org.koin.core.error.NoBeanDefFoundException: No definition found for class:'java.lang.String'. Check your definitions!

I guess defaultValues doesn't work how I might expect. What is the real replacement for create<Box> { parametersOf("foo") }?

This isn't exactly what I want, but let's try putting the parameter directly in the graph.

        val koinApplication = startKoin {
            modules(module {
                single { Box(get()) }
                single { "foo" }
            })
        }

        koinApplication.checkModules()

This fails with a missing MockProvider:

Definition is broken: [Singleton:'Box'] 
- due to error: java.lang.IllegalStateException: Missing MockProvider. Please use MockProvider.register() to register a new mock provider

But why do I need a MockProvider when nothing in the graph needs to be mocked?

Ok, so let's try it this way:

        val koinApplication = startKoin {
            modules(module {
                single { Box(get()) }
                single { "foo" }
            })
        }

        MockProvider.register {
            when (it) {
                String::class -> "bar"
                else -> error("unknown type!")
            }
        }
        koinApplication.checkModules()

This finally works on JVM, but I remain confused. It fails if single { "foo" } is omitted but actually creates a Box using "bar". I don't understand why it uses a mock instead of the value already on the graph. Furthermore, using MockProvider in that way obviously won't scale very well. I guess it's intended to plug in something like Mockk or Mockito but that's only possible on JVM.

Also, that test doesn't work on Native, but fails with

kotlin.native.concurrent.InvalidMutabilityException: mutation attempt of frozen org.koin.test.mock.MockProvider@38510278

In fact, it's impossible to register a mock provider on Native because this involves mutating state in a top-level object which is not allowed by the current memory model.

All told, I find these API breakages confusing and I don't understand how to migrate my koin tests using checkModules() from 3.0.2 to 3.1.0.

[headsvk]

I'm also getting this error for some classes that are part of my graph. I's not clear at all why they should be mocked, I run tests on the emulator.

[arnaudgiuliani]

checkModules API has been reverted in 3.1.1