MockFit

Dependency

allprojects {
 repositories {
 ...
 maven { url 'https://jitpack.io' }
 }
}

dependencies {
 implementation "com.github.javaherisaber.MockFit:runtime:$versions.mockFit"
 kapt "com.github.javaherisaber.MockFit:compiler:$versions.mockFit" // for Kotlin (make sure to include kapt plugin also)
 annotationProcessor "com.github.javaherisaber.MockFit:compiler:$versions.mockFit" // for Java
}

How to use

[
 {
 "id": "1016",
 "author": "Andrew Ridley",
 "width": 3844,
 "height": 2563,
 "url": "https://unsplash.com/photos/_h7aBovKia4",
 "download_url": "https://picsum.photos/id/1018/3914/2935"
 },
 {
 "id": "1018",
 "author": "Andrew Ridley",
 "width": 3914,
 "height": 2935,
 "url": "https://unsplash.com/photos/Kt5hRENuotI",
 "download_url": "https://picsum.photos/id/1018/3914/2935"
 },
 {
 "id": "1019",
 "author": "Patrick Fore",
 "width": 5472,
 "height": 3648,
 "url": "https://unsplash.com/photos/V6s1cmE39XM",
 "download_url": "https://picsum.photos/id/1019/5472/3648"
 }
]

interface Api {
 @Mock("picsum_list.json")
 @GET("list")
 fun getListOfPicsums(
 @Query("page") page: Int,
 @Query("limit") limit: Int
 ): Call<List<Picsum>>
 // if you want to filter through query params
 @Mock("picsum_recent.json", excludeQueries = ["type=favorites"])
 @GET("list")
 fun getRecentPicsums(
 @Query("type") type: String,
 @Query("page") page: Int,
 @Query("limit") limit: Int
 ): Call<List<Picsum>>
 // if you want to filter through query params
 @Mock("picsum_favorites.json", includeQueries = ["type=favorites"])
 @GET("list")
 fun getFavoritePicsums(
 @Query("type") type: String,
 @Query("page") page: Int,
 @Query("limit") limit: Int
 ): Call<List<Picsum>>
}

class RemoteDataSource(private val context: Context) {
 fun api(): Api {
 val mockFitInterceptor = provideMockFitInterceptor(context)
 val okHttpClient = provideOkHttpClient(mockFitInterceptor)
 val retrofit = provideRetrofit(okHttpClient)
 return retrofit.create(Api::class.java)
 }
 private fun provideRetrofit(okHttpClient: OkHttpClient): Retrofit = Retrofit.Builder()
 .baseUrl(BASE_URL)
 .addConverterFactory(GsonConverterFactory.create())
 .client(okHttpClient)
 .build()
 private fun provideMockFitInterceptor(context: Context) = MockFitInterceptor(
 bodyFactory = { input -> context.resources.assets.open(input) }, // read asset file
 logger = { tag, message -> Log.d(tag, message) }, // pass logger to log events in logcat
 baseUrl = BASE_URL, // base url of your api
 requestPathToMockPathRule = REQUEST_TO_JSON, // autogenerated constant, just press build button
 mockFilesPath = MOCK_FILES_PATH, // path to json files
 mockFitEnable = true, // master setting to enable or disable mocking
 apiEnableMock = true, // enable or disable mock when there are includes and excludes configs
 apiIncludeIntoMock = arrayOf(), // include endpoint if `apiEnableMock` is false
 apiExcludeFromMock = arrayOf(), // exclude endpoint if `apiEnableMock` is true 
 apiResponseLatency = 500L // latency of retrieving data
 )
 private fun provideOkHttpClient(mockFitInterceptor: MockFitInterceptor) = OkHttpClient.Builder()
 .addInterceptor(mockFitInterceptor)
 .connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)
 .writeTimeout(WRITE_TIMEOUT, TimeUnit.SECONDS)
 .readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
 .build()
 companion object {
 private const val BASE_URL = "https://picsum.photos/v2/"
 private const val MOCK_FILES_PATH = "mock_json" // located at assets/mock_json/
 private const val CONNECT_TIMEOUT = 20L
 private const val WRITE_TIMEOUT = 20L
 private const val READ_TIMEOUT = 30L
 }
}