Test for Live Data

app/build.gradle

@@ -66,6 +66,7 @@ dependencies {
     testImplementation "androidx.test.ext:junit-ktx:$androidXTestExtKotlinRunnerVersion"
     testImplementation "androidx.test:core-ktx:$androidXTestCoreVersion"
     testImplementation "org.robolectric:robolectric:$robolectricVersion"
+    testImplementation "androidx.arch.core:core-testing:$archTestingVersion"
 
     // AndroidX Test - Instrumented testing
     androidTestImplementation "androidx.test.ext:junit:$androidXTestExtKotlinRunnerVersion"

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

@@ -1,24 +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.google.common.truth.Truth
+import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
 
 
 @RunWith(AndroidJUnit4::class)
 internal class TasksViewModelTest {
 
+    @get:Rule
+    val instantExecutorRule = InstantTaskExecutorRule()
+
     @Test
     fun addNewTask_setNewTask() {
 
         // Assign a ViewModel
         val tasksViewModel = TasksViewModel(ApplicationProvider.getApplicationContext())
+        val observer = Observer<Event<Unit>>{}
+
+        try {
+
+            // Act new Task is added
+            tasksViewModel.newTaskEvent.observeForever(observer)
+            tasksViewModel.addNewTask()
 
-        // Assert adding a new Task
-        tasksViewModel.addNewTask()
+            // Assert adding a new Task
+            val value = tasksViewModel.newTaskEvent.value
+            Truth.assertThat(value?.getContentIfNotHandled()).isNotNull()
 
-        // Act new Task is added
-        // TODO: Test live data.
+        } finally {
+            tasksViewModel.newTaskEvent.removeObserver(observer)
+        }
     }
 }

build.gradle

@@ -50,4 +50,5 @@ ext {
     robolectricVersion = '4.10.3'
     swipeRefreshLayoutVersion = '1.1.0'
     timberVersion = '4.7.1'
+    archTestingVersion = '2.1.0'
 }