How valid is my unit test for the Repository class that logs in to a remote server?

Question

I had to write unit test for my Repository class. I am working on a REST app and I am using Retrofit for communicating with my REST api.

On my ApiInterface I have the following code:

interface ApiInterface {
    /*
    Login to the api
     */
    @POST("api/auth/login")
    fun login(@Body loginFields: LoginFields): Call<LoginResponse>
}

The LoginResponse and LoginFields above are simple data classes

I have my Repository:

class LoginRepository(private val apiInterface: ApiInterface) : ILoginRepository {

    companion object {

        val TAG = LoginRepository::class.java.simpleName
        private var loginRepository: LoginRepository? = null
        private val apiInterface: ApiInterface =
            RetrofitService.createService(ApiInterface::class.java)

        val instance: LoginRepository
            get() {
                if (loginRepository == null) {
                    loginRepository = LoginRepository(apiInterface)
                }
                return loginRepository as LoginRepository
            }
    }

    override fun getUserLogin(loginFields: LoginFields): LiveData<LoginResponse> {

        val loginResponse = MutableLiveData<LoginResponse>()

        apiInterface.login(loginFields).enqueue(object : Callback<LoginResponse> {
            override fun onResponse(
                call: Call<LoginResponse>,
                response: Response<LoginResponse>
            ) {
                if (response.isSuccessful) {
                    loginResponse.postValue(response.body())
                } else {
                    loginResponse.value = null
                    Log.e(TAG, response.errorBody().toString())
                }
            }

            override fun onFailure(call: Call<LoginResponse>, t: Throwable) {
                loginResponse.value = null
                Log.e(TAG, " Failure getting the logged in user")
                t.printStackTrace()
            }
        })
        return loginResponse
    }
}

The ILoginRepository is a simple interface :

interface ILoginRepository {
    fun getUserLogin(loginFields: LoginFields): LiveData<LoginResponse>
}

From what I have heard so far, Unit tests are meant for single units of the code and should not care for other classes. So what I did was create a FakeRepository which implements ILoginRepository and is as follows:

class FakeRepository : ILoginRepository {
    override fun getUserLogin(loginFields: LoginFields): LiveData<LoginResponse> {
        val liveData: MutableLiveData<LoginResponse> = MutableLiveData()
        liveData.postValue(
            LoginResponse(
                "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImp0aSI6ImU3NjIxNjBmNTMxN2NlMmZiMDc0NzcxODQ1MTJjZGVjZmE4NmVkNmI3Njg5ZmM1N2UzOWYyMDJhNTQyODZlOTZlN2I3OWZjMDZhZTliODYyIn0.eyJhdWQiOiI1IiwianRpIjoiZTc2MjE2MGY1MzE3Y2UyZmIwNzQ3NzE4NDUxMmNkZWNmYTg2ZWQ2Yjc2ODlmYzU3ZTM5ZjIwMmE1NDI4NmU5NmU3Yjc5ZmMwNmFlOWI4NjIiLCJpYXQiOjE1NzQwNjA4NzUsIm5iZiI6MTU3NDA2MDg3NSwiZXhwIjoxNjA1NjgzMjc0LCJzdWIiOiIzNiIsInNjb3BlcyI6W119.S77D2pG7ScQn7ufyyVG2fhnydKWJUUv3Khotqt4K41ylP_7VWqNmIzUr0ZfeuryWvRHj0qP8kEG4hIbbfmFOnEHQBwTCVEyV7LNaazYLg9VIvXeHiQ99vZHVSyBwy-ENY772YxpBHCPy6aG5ziQM1LK357mOoIQiucLXGe1lQkwXSlqULuEqt-5tsDAgnMPz48d6cEzVF9muU2PjgwNThcPUyNkivlzHuzsj7pQWum7bALHPzcoQRNGzEzhICShCtEBQ_T0VbMakcY2Iwl2rQuxWPBiFjpNv69VfXjAxXuYkbRpRfbIiNIBuaHWOlvkOHQAbUELg6Nd88L78UN4z91SBhN6JVB3kG8ibHSHT7ip4ruLiXSRtDROX3I_mpMx_7gcqK80L2FqxnznTLbg39Mgkfsu56TbGd2NTtHBcif66SUPXsrIM-kGIvsajUz-x3VHFJvJvAvZ5zSKMq5c4pTkDYCv4g6-o7fEX3bIT94m89K5drAub8iluRFyXNnhSMi29JpSxU6LeMmuaZGvQssm170oY76ZOMe3xwVMzWatXVHtpsl51M2iC2JhXq9Z-pxd1ZAx8_HVbG01OOpqcqKoFbTFtgsl8mIxDsU91aBDHN_xqXO6EUTdm7Gz4TOo1_C5m1R5nYWuGngAXfIFzlF4L6gBUokJPs8KDPxNrBdk",
                "Bearer",
                "2020-11-18 12:52:54",
                User(
                    35,
                    "Prashanna Bhandary",
                    loginFields.email,
                    "dd58a617ea618010c2052cb54079ad67.jpeg",
                    "98********",
                    "test address 01",
                    1,
                    "yes",
                    "2019-08-30 04:56:43",
                    "2019-08-30 05:14:47",
                    0
                )
            )
        )
        return liveData
    }
}

You can see what I am doing here.

Now to test the Repository, I made a unit test class like following:

class LoginRepositoryTest {
    @get:Rule
    val instantTaskExecutorRule = InstantTaskExecutorRule()
    //data input
    val loginFields = LoginFields("test@test.com", "test@123")
    //expected
    val correctLoginResponse = LoginResponse(
        "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiIsImp0aSI6ImU3NjIxNjBmNTMxN2NlMmZiMDc0NzcxODQ1MTJjZGVjZmE4NmVkNmI3Njg5ZmM1N2UzOWYyMDJhNTQyODZlOTZlN2I3OWZjMDZhZTliODYyIn0.eyJhdWQiOiI1IiwianRpIjoiZTc2MjE2MGY1MzE3Y2UyZmIwNzQ3NzE4NDUxMmNkZWNmYTg2ZWQ2Yjc2ODlmYzU3ZTM5ZjIwMmE1NDI4NmU5NmU3Yjc5ZmMwNmFlOWI4NjIiLCJpYXQiOjE1NzQwNjA4NzUsIm5iZiI6MTU3NDA2MDg3NSwiZXhwIjoxNjA1NjgzMjc0LCJzdWIiOiIzNiIsInNjb3BlcyI6W119.S77D2pG7ScQn7ufyyVG2fhnydKWJUUv3Khotqt4K41ylP_7VWqNmIzUr0ZfeuryWvRHj0qP8kEG4hIbbfmFOnEHQBwTCVEyV7LNaazYLg9VIvXeHiQ99vZHVSyBwy-ENY772YxpBHCPy6aG5ziQM1LK357mOoIQiucLXGe1lQkwXSlqULuEqt-5tsDAgnMPz48d6cEzVF9muU2PjgwNThcPUyNkivlzHuzsj7pQWum7bALHPzcoQRNGzEzhICShCtEBQ_T0VbMakcY2Iwl2rQuxWPBiFjpNv69VfXjAxXuYkbRpRfbIiNIBuaHWOlvkOHQAbUELg6Nd88L78UN4z91SBhN6JVB3kG8ibHSHT7ip4ruLiXSRtDROX3I_mpMx_7gcqK80L2FqxnznTLbg39Mgkfsu56TbGd2NTtHBcif66SUPXsrIM-kGIvsajUz-x3VHFJvJvAvZ5zSKMq5c4pTkDYCv4g6-o7fEX3bIT94m89K5drAub8iluRFyXNnhSMi29JpSxU6LeMmuaZGvQssm170oY76ZOMe3xwVMzWatXVHtpsl51M2iC2JhXq9Z-pxd1ZAx8_HVbG01OOpqcqKoFbTFtgsl8mIxDsU91aBDHN_xqXO6EUTdm7Gz4TOo1_C5m1R5nYWuGngAXfIFzlF4L6gBUokJPs8KDPxNrBdk",
        "Bearer",
        "2020-11-18 12:52:54",
        User(
            35,
            "Prashanna Bhandary",
            loginFields.email,
            "dd58a617ea618010c2052cb54079ad67.jpeg",
            "98********",
            "test address 01",
            1,
            "yes",
            "2019-08-30 04:56:43",
            "2019-08-30 05:14:47",
            0
        )
    )
    //class under test
    private lateinit var loginRepository: FakeRepository
    @Before
    fun setUp() {
        loginRepository = FakeRepository()
        ServiceLocator.loginRepository = loginRepository
    }
    @Test
    fun correctLoginFields_geUserLogin_shouldGiveLoginResponse() {
        //when
        val loginResponse = loginRepository.getUserLogin(loginFields).value
        //then
        assertEquals(correctLoginResponse, loginResponse)
    }
}

So I guess what my question is: How valid is my Unit Test? Is this how we are supposed to unit test things? Does this unit test provide me any value?

Answer 1

• Does this unit test provide me any value? : No value (until you use FakeRepository in production)

This test code is testing FakeRepository. I think you want to test LoginRepository which is an ILoginRepository implementation. Because you're not going to use FakeRepository in production, isn't it?

I'll explain briefly how to unit test. You need to instantiate the class Foo you want to test and mock the classes it depends on.

Let's see your code. The important part is below code.

interface ApiInterface {
    @POST("api/auth/login")
    fun login(@Body loginFields: LoginFields): Call<LoginResponse>
}

class LoginRepository(private val apiInterface: ApiInterface) : ILoginRepository { ... }

So in your case, you have to mock ApiInterface. And instantiate LoginRepository. But mocking ApiInterface is too hard because it depends on Retrofit class such as Call.

To solve these problems simply, you need OkHttp MockWebServer.