This is why we use DI...

Author: JoseAlcerreca

app/src/androidTestMock/java/com/example/android/architecture/blueprints/todoapp/tasks/TasksActivityTest.kt

@@ -33,6 +33,7 @@ import androidx.test.espresso.matcher.ViewMatchers.withId
 import androidx.test.espresso.matcher.ViewMatchers.withText
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.filters.LargeTest
+import androidx.test.internal.runner.junit4.statement.UiThreadStatement.runOnUiThread
 import com.example.android.architecture.blueprints.todoapp.R
 import com.example.android.architecture.blueprints.todoapp.R.string
 import com.example.android.architecture.blueprints.todoapp.ServiceLocator
@@ -67,13 +68,19 @@ class TasksActivityTest {
 
     @Before
     fun init() {
-        repository = ServiceLocator.provideTasksRepository(getApplicationContext())
-        repository.deleteAllTasksBlocking()
+        // Run on UI thread to make sure the same instance of the SL is used.
+        runOnUiThread {
+            ServiceLocator.createDataBase(getApplicationContext(), inMemory = true)
+            repository = ServiceLocator.provideTasksRepository(getApplicationContext())
+            repository.deleteAllTasksBlocking()
+        }
     }
 
     @After
     fun reset() {
-        ServiceLocator.resetRepository()
+        runOnUiThread {
+            ServiceLocator.resetRepository()
+        }
     }
 
     /**

app/src/mock/java/com/example/android/architecture/blueprints/todoapp/ServiceLocator.kt

@@ -55,11 +55,23 @@ object ServiceLocator {
         return TasksLocalDataSource(database.taskDao())
     }
 
-    private fun createDataBase(context: Context): ToDoDatabase {
-        val result = Room.databaseBuilder(
-            context.applicationContext,
-            ToDoDatabase::class.java, "Tasks.db"
-        ).build()
+    @VisibleForTesting
+    fun createDataBase(
+        context: Context,
+        inMemory: Boolean = false
+    ): ToDoDatabase {
+        val result = if (inMemory) {
+            // Use a faster in-memory database for tests
+            Room.inMemoryDatabaseBuilder(context.applicationContext, ToDoDatabase::class.java)
+                .allowMainThreadQueries()
+                .build()
+        } else {
+            // Real database using SQLite
+            Room.databaseBuilder(
+                context.applicationContext,
+                ToDoDatabase::class.java, "Tasks.db"
+            ).build()
+        }
         database = result
         return result
     }