Part 9: Unit Tests with Mockito + RxJava TestSubscriber

app/build.gradle

@@ -41,6 +41,9 @@ dependencies {
     // Retrofit
     compile "com.squareup.retrofit2:retrofit:2.0.0"
     compile "com.squareup.retrofit2:converter-moshi:2.0.0"
+
+    // Tests
+    testCompile "org.mockito:mockito-core:1.+"
 }
 buildscript {
     ext.kotlin_version = '1.0.2'

app/src/main/java/com/droidcba/kedditbysteps/api/NewsAPI.kt

@@ -0,0 +1,12 @@
+package com.droidcba.kedditbysteps.api
+
+import retrofit2.Call
+
+/**
+ * News API
+ *
+ * @author juancho.
+ */
+interface NewsAPI {
+    fun getNews(after: String, limit: String): Call<RedditNewsResponse>
+}

app/src/main/java/com/droidcba/kedditbysteps/api/RestAPI.kt → app/src/main/java/com/droidcba/kedditbysteps/api/NewsRestAPI.kt

@@ -4,7 +4,7 @@ import retrofit2.Call
 import retrofit2.Retrofit
 import retrofit2.converter.moshi.MoshiConverterFactory
 
-class RestAPI() {
+class NewsRestAPI() : NewsAPI {
 
     private val redditApi: RedditApi
 
@@ -17,7 +17,7 @@ class RestAPI() {
         redditApi = retrofit.create(RedditApi::class.java)
     }
 
-    fun getNews(after: String, limit: String): Call<RedditNewsResponse> {
+    override fun getNews(after: String, limit: String): Call<RedditNewsResponse> {
         return redditApi.getTop(after, limit)
     }
 }

app/src/main/java/com/droidcba/kedditbysteps/features/news/NewsManager.kt

@@ -1,6 +1,7 @@
 package com.droidcba.kedditbysteps.features.news
 
-import com.droidcba.kedditbysteps.api.RestAPI
+import com.droidcba.kedditbysteps.api.NewsAPI
+import com.droidcba.kedditbysteps.api.NewsRestAPI
 import com.droidcba.kedditbysteps.commons.RedditNews
 import com.droidcba.kedditbysteps.commons.RedditNewsItem
 import rx.Observable
@@ -10,7 +11,7 @@ import rx.Observable
  *
  * @author juancho
  */
-class NewsManager(private val api: RestAPI = RestAPI()) {
+class NewsManager(private val api: NewsAPI = NewsRestAPI()) {
 
     /**
      *

app/src/test/java/com/droidcba/kedditbysteps/NewsManagerTest.kt

@@ -0,0 +1,102 @@
+package com.droidcba.kedditbysteps
+
+import com.droidcba.kedditbysteps.api.*
+import com.droidcba.kedditbysteps.commons.RedditNews
+import com.droidcba.kedditbysteps.features.news.NewsManager
+import okhttp3.MediaType
+import okhttp3.ResponseBody
+import org.junit.Before
+import org.junit.Test
+import org.mockito.Mockito
+import org.mockito.Mockito.`when`
+import org.mockito.Mockito.anyString
+import retrofit2.Call
+import retrofit2.Response
+import rx.observers.TestSubscriber
+import java.util.*
+
+/**
+ * Unit Tests for NewsManager
+ *
+ * @author juancho.
+ */
+class NewsManagerTest {
+
+    var testSub = TestSubscriber<RedditNews>()
+    var apiMock = mock<NewsAPI>()
+    var callMock = mock<Call<RedditNewsResponse>>()
+
+    @Before
+    fun setup() {
+        testSub = TestSubscriber<RedditNews>()
+        apiMock = mock<NewsAPI>()
+        callMock = mock<Call<RedditNewsResponse>>()
+        `when`(apiMock.getNews(anyString(), anyString())).thenReturn(callMock)
+    }
+
+    @Test
+    fun testSuccess_basic() {
+        // prepare
+        val redditNewsResponse = RedditNewsResponse(RedditDataResponse(listOf(), null, null))
+        val response = Response.success(redditNewsResponse)
+
+        `when`(callMock.execute()).thenReturn(response)
+
+        // call
+        val newsManager = NewsManager(apiMock)
+        newsManager.getNews("").subscribe(testSub)
+
+        // assert
+        testSub.assertNoErrors()
+        testSub.assertValueCount(1)
+        testSub.assertCompleted()
+    }
+
+    @Test
+    fun testSuccess_checkOneNews() {
+        // prepare
+        val newsData = RedditNewsDataResponse(
+                "author",
+                "title",
+                10,
+                Date().time,
+                "thumbnail",
+                "url"
+        )
+        val newsResponse = RedditChildrenResponse(newsData)
+        val redditNewsResponse = RedditNewsResponse(RedditDataResponse(listOf(newsResponse), null, null))
+        val response = Response.success(redditNewsResponse)
+
+        `when`(callMock.execute()).thenReturn(response)
+
+        // call
+        val newsManager = NewsManager(apiMock)
+        newsManager.getNews("").subscribe(testSub)
+
+        // assert
+        testSub.assertNoErrors()
+        testSub.assertValueCount(1)
+        testSub.assertCompleted()
+
+        assert(testSub.onNextEvents[0].news[0].author == newsData.author)
+        assert(testSub.onNextEvents[0].news[0].title == newsData.title)
+    }
+
+    @Test
+    fun testError() {
+        // prepare
+        val responseError = Response.error<RedditNewsResponse>(500,
+                ResponseBody.create(MediaType.parse("application/json"), ""))
+
+        `when`(callMock.execute()).thenReturn(responseError)
+
+        // call
+        val newsManager = NewsManager(apiMock)
+        newsManager.getNews("").subscribe(testSub)
+
+        // assert
+        assert(testSub.onErrorEvents.size == 1)
+    }
+}
+
+inline fun <reified T : Any> mock(): T = Mockito.mock(T::class.java)