Testing Kotlin Extension Functions with Spring - spring

Question

I have a controller that gets a specific service based on a customer name:
#RestController
class BasicController(){
#Autowired
private lateinit var services: List<BasicService<*>>
private var service: BasicService<*>? = null
#GetMapping("/{customer}")
fun getAll(#PathVariable customer: String): ResponseEntity<String>{
service = services.getServiceByCustomer(customer)
/... code w/return value .../
}
}
I have a file Extensions.kt with the following:
fun <T: BasicService> List<T>.getServiceByCustomer(customer: String): T?{
return this.find{
it::class.simpleName?.contains(customer, ignoreCase = true) == true
}
}
Is it possible to return a mock of service when services.getServiceByCustomer is called similar to `when`(mock.function(anyString())).thenReturn(value)?
I've tried using mockK with the following:
mockkStatic("path.to.ExtensionsKt")
every {listOf(service).getServiceByCustomer)} returns service
But I don't think I'm using that properly... I'm currently using com.nhaarman.mockitokotlin2 but have tried io.mockk

Answer 1

You just need to use a customer that actually matches the simple name of the mocked service. You don't need or even should mock the extension function. Try the following:
class BasicControllerTest {
#MockK
private lateinit var basicService: BasicService
private lateinit var basicController: BasicController
#BeforeEach
fun setUp() {
clearAllMocks()
basicController = BasicController(listOf(basicService))
}
}
Additionally, consider using constructor injection instead of field injection:
#RestController
class BasicController(private val services: List<BasicService<*>>){
private var service: BasicService<*>? = null
#GetMapping("/{customer}")
fun getAll(#PathVariable customer: String): ResponseEntity<String>{
service = services.getServiceByCustomer(customer)
/... code w/return value .../
}
}
Finally, consider testing the Controllers with #WebMvcTest instead of regular unit tests. Check more info here https://www.baeldung.com/spring-boot-testing#unit-testing-with-webmvctest.