How to Use Mockito in Kotlin

Is it possible to use Mockito in Kotlin?

There are two possible workarounds:

private fun <T> anyObject(): T {
    Mockito.anyObject<T>()
    return uninitialized()
}

private fun <T> uninitialized(): T = null as T

@Test
fun myTest() {
    `when`(mockedBackend).login(anyObject())).thenAnswer { ... }
}

The other workaround is

private fun <T> anyObject(): T {
    return Mockito.anyObject<T>()
}

@Test
fun myTest() {
    `when`(mockedBackend).login(anyObject())).thenAnswer { ... }
}

Here is some more discussion on this topic, where the workaround is first suggested.

Is it possible to use Mockito with Kotlin without open the class?

Mockito2 can now mock final classes as well.

However, this feature is opt-in, so you need to enable it manually.

To do so, you need to define a file /mockito-extensions/org.mockito.plugins.MockMaker containing the line mock-maker-inline

See e.g.

http://hadihariri.com/2016/10/04/Mocking-Kotlin-With-Mockito/ or
https://github.com/mockito/mockito/wiki/What%27s-new-in-Mockito-2#unmockable

for a quick introduction

on a side note, this currently doesn't work for android

Mockito with Kotlin Controller class

The whole test class seems a bit messy to me... You are using the @EnableSpringDataWebSupport @RunWith(MockitoJUnitRunner::class) annotations. The standard way how to test your controller is by using the @WebMvcTest annotation - see https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#boot-features-testing-spring-boot-applications-testing-autoconfigured-mvc-tests.

Then your test class should look something like this:

@WebMvcTest(controllers = [SmelterController::class])
internal class SmelterControllerTest @Autowired constructor(
    private val mockMvc: MockMvc,
) {
    @MockBean
    private lateinit var smelterService: SmelterService
    @MockBean
    private lateinit var smelterMapper: SmelterMapper

    @Test
    fun `list all smelters returns one item`() {
        // mock behaviour of smelterService.listAll
        // mock behaviour of smelterMapper.toDtoPage

        // perform mockMvc call

        // verify mocks
    }
}

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