Unit test rest controller in kotlin + Spring boot

Question

Edit: I've created another class "Utils" and moved function to that class.

class Utils {
fun isMaintenanceFileExist(maintenanceFile: String) : Boolean {
    /** method to check maintenance file, return True if found else False. */
    return File(maintenanceFile).exists()
}
}

I'm testing post API and mocking a method like below:

@Test
fun testMaintenanceMode() {
    val mockUtil = Mockito.mock(Utils::class.java)
    Mockito.`when`(mockUtil.isMaintenanceFileExist("maintenanceFilePath"))
            .thenReturn(true)

    // Request body
    val body = "authId=123&[email protected]&confirmationKey=86b498cb7a94a3555bc6ee1041a1c90a"

    // When maintenance mode is on
    mvc.perform(MockMvcRequestBuilders.post("/post")
            .contentType(MediaType.APPLICATION_FORM_URLENCODED_VALUE)
            .content(body))
            .andExpect(MockMvcResultMatchers.status().isBadRequest)
            .andReturn()
    }

But I'm not getting expected results.

Controller code:

{
utilObj = Utils()
...
@PostMapping("/post")
fun registerByMail(@Valid data: RequestData) : ResponseEntity<Any>
{

    // check for maintenance mode, if True return (error code : 9001)
    if(utilObj.isMaintenanceFileExist("maintenanceFilePath")) {
        println("-------- Maintenance file exist. Exiting. --------")
        var error = ErrorResponse(Response(ResponseCode.MAINTENANCE,
                ResponseCode.MAINTENANCE.toString()))
        return ResponseEntity.badRequest().body(error)
}
...
}

I want to return true from isMaintenanceFileExist() method in test and want to check for badRequest. Please guide how to achieve this.

Answer 1

From looking at your code snippets I would guess that you're not actually using the mocked Controller instance in your tests. The controller is instantiated by the Spring Boot test runner and not using your mock instance.

I would recommend to extract the isMaintenanceFileExist method into a separate bean and then mock it using @MockBean.

Controller and Util Bean

@RestController
class MyController(@Autowired private val utils: Utils) {

    @PostMapping("/post")
    fun registerByMail(@RequestBody data: String): ResponseEntity<Any> {

        if (utils.isMaintenanceFileExist("maintenanceFilePath")) {
            println("-------- Maintenance file exist. Exiting. --------")
            return ResponseEntity.badRequest().body("error")
        }
        return ResponseEntity.ok("ok")
    }

}

@Component
class Utils {
    fun isMaintenanceFileExist(maintenanceFile: String) = File(maintenanceFile).exists()
}

Test Class

@WebMvcTest(MyController::class)
class DemoApplicationTests {

    @MockBean
    private lateinit var utils: Utils

    @Autowired
    private lateinit var mvc: MockMvc

    @Test
    fun testMaintenanceMode() {
        BDDMockito.given(utils.isMaintenanceFileExist("maintenanceFilePath"))
                .willReturn(true)

        val body = "test"

        mvc.perform(MockMvcRequestBuilders.post("/post")
                .contentType(MediaType.TEXT_PLAIN)
                .content(body))
                .andExpect(MockMvcResultMatchers.status().isBadRequest)
    }

}

See chapter 44.3.7.