Test Retrofit with mock web server

RetrofitTest.kt

// testImplementation "com.squareup.okhttp3:mockwebserver:4.7.2"

class RetrofitTest {

    @get:Rule
    private val server = MockWebServer().apply { dispatcher = MockDispatcher() }
    private lateinit var api: Api

    @Before
    fun setup() {
        api = Retrofit.Builder()
            .baseUrl(server.url("/").toString())
            .client(OkHttpClient.Builder().build())
            .addConverterFactory(GsonConverterFactory.create(Gson()))
            .build()
            .create(Api::class.java)
    }

    @Test
    fun `test success response`() {
        runBlocking {
            val response = api.login(LoginRequest("user", "pass"))

            Assert.assertEquals(true, response.isSuccessful)
            Assert.assertEquals("token", response.body()?.token)
        }
    }

    @Test
    fun `test fail response`() {
        runBlocking {
            val response = api.register(LoginRequest("user", "pass"))

            Assert.assertEquals(false, response.isSuccessful)
            Assert.assertEquals(null, response.body()?.token)
            Assert.assertEquals("{\"errorMessage\":\"failed\"}", response.errorBody()?.string())
        }
    }
}


class MockDispatcher : QueueDispatcher() {

    override fun dispatch(request: RecordedRequest): MockResponse {

        return when (request.path) {
            "/login" -> MockResponse()
                .setResponseCode(200)
                .setBody("{\"token\":\"token\"}")
            else -> MockResponse()
                .setResponseCode(412)
                .setBody("{\"errorMessage\":\"failed\"}")
        }
    }
}