Using Koin for android tests

[AntoineJaury]

Searching for a solution to mock one of my repositories used as a Koin Module for instrumented tests, I finally found a way to mock it.

If you want to mock one of the Koin Modules for your instrumented test, you need to call the loadKoinModules method passing it a list of Koin Modules you want to override.

The problem here is that if the Koin Module you want override is already injected inside the components you want to test, then the loadKoinModules won't have any effect on these components. So you have to make sure the Koin Module is not injected in your components before mocking it.

A workaround I found is to override the ActivityTestRule you defined in your test class and to mock your Koin Module during the beforeActivityLaunchedof the ActivityTestRule.

This way, the Koin module will be mocked before activity is launched. As the module was injected once the Activity was created in my side, this solved the problem.

Here is my Test class including this solution:

@RunWith(AndroidJUnit4::class)
class LoginTest {

    val mockedUserRepository = Mockito.mock(UserDataSource::class.java)

    @Rule
    @JvmField
    val rule = object: ActivityTestRule<LoginActivity>(LoginActivity::class.java) {
        override fun beforeActivityLaunched() {
            super.beforeActivityLaunched()

            // This will replace the UserDataSource module previously defined 
            // in the Application class creation before the activity is launched
            // Otherwise ... components won't be reloaded
            val mockedUserModule = applicationContext {
                bean { mockedUserRepository as UserDataSource }
            }
            loadKoinModules(listOf(mockedUserModule))
        }
    }
   
   @Test
   fun loginWithUnactivatedAccount() {
        // Here the new module is loaded with all application components
        // and you can interact with the mockedUserRepository 
        ... 
   }
}

It would be great to have such example inside the documentation :)

[patrice-conil]

Hi all,
I confirm that testing activity is a pain when we need to inject mock instances.
I think that an @MockBean annotation as in spring would be of great help.
In spring this annotation replaces the corresponding bean by the annotated mock.
This simplify greatly the test writing.
Patrice

[arnaudgiuliani]

Hi @patrice-conil,

could be interesting to tell to Koin that we want mocks for given types 👍

[arnaudgiuliani]

In the snippet above, we can replace the snippet:

val mockedUserRepository = Mockito.mock(UserDataSource::class.java)

    @Rule
    @JvmField
    val rule = object: ActivityTestRule<LoginActivity>(LoginActivity::class.java) {
        override fun beforeActivityLaunched() {
            super.beforeActivityLaunched()

            // This will replace the UserDataSource module previously defined 
            // in the Application class creation before the activity is launched
            // Otherwise ... components won't be reloaded
            val mockedUserModule = applicationContext {
                bean { mockedUserRepository as UserDataSource }
            }
            loadKoinModules(listOf(mockedUserModule))
        }
    }

with:

 val rule = object: ActivityTestRule<LoginActivity>(LoginActivity::class.java) {
        override fun beforeActivityLaunched() {
            super.beforeActivityLaunched()

            // This will replace the UserDataSource module previously defined 
            // in the Application class creation before the activity is launched
           declareMock<UserDataSource>()
        }
    }

I've just added createMock() function in koin-test

[arnaudgiuliani]

Check #151

[jerryOkafor]

Can not see the createMock() function in koin test

[arnaudgiuliani]

Sorry, it's has been renamed declareMock (createMock was conflicting with other API).