[Do not merge] Learning Codelab

app/build.gradle

@@ -60,4 +60,16 @@ dependencies {
     // Kotlin
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
     implementation "androidx.fragment:fragment-ktx:$fragmentKtxVersion"
+
+    // Other dependencies
+    testImplementation "org.hamcrest:hamcrest-all:$hamcrestVersion"
+
+    // AndroidX Test - JVM testing
+    testImplementation "androidx.test.ext:junit-ktx:$androidXTestExtKotlinRunnerVersion"
+    testImplementation "androidx.test:core-ktx:$androidXTestCoreVersion"
+    testImplementation "org.robolectric:robolectric:$robolectricVersion"
+
+    // Architecture Components core testing library (for LiveData test)
+    testImplementation "androidx.arch.core:core-testing:$archTestingVersion"
+
 }

app/src/main/java/com/example/android/architecture/blueprints/todoapp/statistics/StatisticsUtils.kt

@@ -22,12 +22,16 @@ import com.example.android.architecture.blueprints.todoapp.data.Task
  * Function that does some trivial computation. Used to showcase unit tests.
  */
 internal fun getActiveAndCompletedStats(tasks: List<Task>?): StatsResult {
-    val totalTasks = tasks!!.size
-    val numberOfActiveTasks = tasks.count { it.isActive }
-    return StatsResult(
-        activeTasksPercent = 100f * numberOfActiveTasks / tasks.size,
-        completedTasksPercent = 100f * (totalTasks - numberOfActiveTasks) / tasks.size
-    )
+    return if (tasks == null || tasks.isEmpty()) {
+        StatsResult(0f, 0f)
+    } else {
+        val totalTasks = tasks.size
+        val numberOfActiveTasks = tasks.count { it.isActive }
+        StatsResult(
+            activeTasksPercent = 100f * numberOfActiveTasks / tasks.size,
+            completedTasksPercent = 100f * (totalTasks - numberOfActiveTasks) / tasks.size
+        )
+    }
 }
 
 data class StatsResult(val activeTasksPercent: Float, val completedTasksPercent: Float)

app/src/main/java/com/example/android/architecture/blueprints/todoapp/tasks/TasksViewModel.kt

@@ -160,6 +160,7 @@ class TasksViewModel(application: Application) : AndroidViewModel(application) {
     /**
      * Called by the Data Binding library and the FAB's click listener.
      */
+    // local test 수행할 함수
     fun addNewTask() {
         _newTaskEvent.value = Event(Unit)
     }

app/src/test/java/com/example/android/architecture/blueprints/todoapp/LiveDataTestUtil.kt

@@ -0,0 +1,45 @@
+package com.example.android.architecture.blueprints.todoapp
+
+import androidx.annotation.VisibleForTesting
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.Observer
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.TimeoutException
+
+
+/**
+ * observeForever()로 등록된 옵저버를 해제하도록 작성된 확장 함수.
+ */
+@VisibleForTesting(otherwise = VisibleForTesting.NONE)
+fun <T> LiveData<T>.getOrAwaitValue(
+    time: Long = 2,
+    timeUnit: TimeUnit = TimeUnit.SECONDS,
+    afterObserve: () -> Unit = {}
+): T {
+    var data: T? = null
+    val latch = CountDownLatch(1)
+    val observer = object : Observer<T> {
+        override fun onChanged(o: T?) {
+            data = o
+            latch.countDown()
+            this@getOrAwaitValue.removeObserver(this)
+        }
+    }
+    this.observeForever(observer)
+
+    try {
+        afterObserve.invoke()
+
+        // Don't wait indefinitely if the LiveData is not set.
+        if (!latch.await(time, timeUnit)) {
+            throw TimeoutException("LiveData value was never set.")
+        }
+
+    } finally {
+        this.removeObserver(observer)
+    }
+
+    @Suppress("UNCHECKED_CAST")
+    return data as T
+}

app/src/test/java/com/example/android/architecture/blueprints/todoapp/statistics/StatisticsUtilsTest.kt

@@ -0,0 +1,79 @@
+package com.example.android.architecture.blueprints.todoapp.statistics
+
+import com.example.android.architecture.blueprints.todoapp.data.Task
+import org.hamcrest.CoreMatchers.`is`
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.Test
+
+class StatisticsUtilsTest {
+
+    // 1. 앞서 생성한 테스트 클래스를 open
+    // 2. 테스트 함수를 생성.
+    // 3. 테스트임을 나타내기 위해 함수 이름 위에 @Test annotation을 추가.
+    @Test
+    fun getActiveAndCompletedStats_완료된작업이없으면_100과_0으로_계산되는가() {
+
+        // 4. 작업 목록 만들기
+        val tasks = listOf<Task>(
+            Task("title", "desc", isCompleted = false)
+        )
+        // 5. 계산 함수인 getActiveAndCompletedStats()를 호출
+        val result = getActiveAndCompletedStats(tasks)
+
+        // 6. assertion을 사용하여 결과를 확인
+        assertThat(result.completedTasksPercent, `is`(0f))
+        assertThat(result.activeTasksPercent, `is`(100f))
+    }
+
+    @Test
+    fun getActiveAndCompletedStats_활성화된작업이없으면_0과_100으로_계산되는가() {
+        val tasks = listOf(
+            Task("title", "desc", isCompleted = true)
+        )
+        // When the list of tasks is computed with a completed task
+        val result = getActiveAndCompletedStats(tasks)
+
+        // Then the percentages are 0 and 100
+        assertThat(result.activeTasksPercent, `is`(0f))
+        assertThat(result.completedTasksPercent, `is`(100f))
+    }
+
+    @Test
+    fun getActiveAndCompletedStats_active와complete두경우모두_제대로계산되는가() {
+        // Given 3 completed tasks and 2 active tasks
+        val tasks = listOf(
+            Task("title", "desc", isCompleted = true),
+            Task("title", "desc", isCompleted = true),
+            Task("title", "desc", isCompleted = true),
+            Task("title", "desc", isCompleted = false),
+            Task("title", "desc", isCompleted = false)
+        )
+        // When the list of tasks is computed
+        val result = getActiveAndCompletedStats(tasks)
+
+        // Then the result is 40-60
+        assertThat(result.activeTasksPercent, `is`(40f))
+        assertThat(result.completedTasksPercent, `is`(60f))
+    }
+
+    @Test
+    fun getActiveAndCompletedStats_null이입력되면_0을리턴하는가() {
+        // When there's an error loading stats
+        val result = getActiveAndCompletedStats(null)
+
+        // Both active and completed tasks are 0
+        assertThat(result.activeTasksPercent, `is`(0f))
+        assertThat(result.completedTasksPercent, `is`(0f))
+    }
+
+    @Test
+    fun getActiveAndCompletedStats_빈리스트가입력되면_0을리턴하는가() {
+        // When there are no tasks
+        val result = getActiveAndCompletedStats(emptyList())
+
+        // Both active and completed tasks are 0
+        assertThat(result.activeTasksPercent, `is`(0f))
+        assertThat(result.completedTasksPercent, `is`(0f))
+    }
+
+}

app/src/test/java/com/example/android/architecture/blueprints/todoapp/tasks/TasksViewModelTest.kt

@@ -0,0 +1,41 @@
+package com.example.android.architecture.blueprints.todoapp.tasks
+
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import androidx.lifecycle.Observer
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import com.example.android.architecture.blueprints.todoapp.Event
+import com.example.android.architecture.blueprints.todoapp.getOrAwaitValue
+import org.hamcrest.CoreMatchers.not
+import org.hamcrest.CoreMatchers.nullValue
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.Rule
+
+import org.junit.Test
+import org.junit.runner.RunWith
+
+// AndroidX Test 라이브러리의 annotation
+@RunWith(AndroidJUnit4::class)
+class TasksViewModelTest {
+
+    @get:Rule
+    var instantExecutorRule = InstantTaskExecutorRule()
+
+    @Test
+    fun addNewTask_setsNewTaskEvent() {
+
+        // Given a fresh ViewModel
+        // AndroidX Test 라이브러리로부터 applicationContext를 얻어와 뷰모델을 생성한다.
+        val tasksViewModel = TasksViewModel(ApplicationProvider.getApplicationContext())
+
+        // When adding a new task
+        tasksViewModel.addNewTask()
+
+        // Then the new task event is triggered
+        val value = tasksViewModel.newTaskEvent.getOrAwaitValue()
+
+        // LiveData 캐싱 이슈 방지를 위한 getContentIfNotHandled() 호출 참고.
+        assertThat(value.getContentIfNotHandled(), (not(nullValue())))
+    }
+
+}

build.gradle

@@ -48,4 +48,7 @@ ext {
     rulesVersion = '1.0.1'
     swipeRefreshLayoutVersion = '1.1.0'
     timberVersion = '4.7.1'
+    hamcrestVersion = '1.3'
+    robolectricVersion = '4.4'
+    archTestingVersion = '2.1.0'
 }