Testing UserDao

app/src/androidTest/java/com/ericampire/android/androidstudycase/room/CoroutineTestRule.kt

@@ -0,0 +1,26 @@
+package com.ericampire.android.androidstudycase.room
+
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.TestCoroutineDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.setMain
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+
+@ExperimentalCoroutinesApi
+class CoroutineTestRule(
+  val testDispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher()
+) : TestWatcher() {
+
+  override fun starting(description: Description?) {
+    super.starting(description)
+    Dispatchers.setMain(testDispatcher)
+  }
+
+  override fun finished(description: Description?) {
+    super.finished(description)
+    Dispatchers.resetMain()
+    testDispatcher.cleanupTestCoroutines()
+  }
+}

app/src/androidTest/java/com/ericampire/android/androidstudycase/room/UserDaoTest.kt

@@ -0,0 +1,62 @@
+package com.ericampire.android.androidstudycase.room
+
+import android.content.Context
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import app.cash.turbine.test
+import com.ericampire.android.androidstudycase.app.room.AppDatabase
+import com.ericampire.android.androidstudycase.data.room.UserDao
+import com.ericampire.android.androidstudycase.util.PreviewData
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.test.*
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
+import org.junit.After
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import java.io.IOException
+import kotlin.time.ExperimentalTime
+
+@RunWith(AndroidJUnit4::class)
+@ExperimentalCoroutinesApi
+@ExperimentalTime
+class UserDaoTest {
+
+  private val testDispatcher = TestCoroutineDispatcher()
+  private val testScope = TestCoroutineScope(testDispatcher)
+
+  private lateinit var userDao: UserDao
+  private lateinit var db: AppDatabase
+
+  @Before
+  fun setupDispatcher() {
+    Dispatchers.setMain(testDispatcher)
+  }
+
+
+  @Before
+  fun createDb() {
+    val context = ApplicationProvider.getApplicationContext<Context>()
+    db = Room.inMemoryDatabaseBuilder(context, AppDatabase::class.java).build()
+    userDao = db.userDao
+  }
+
+  @Test
+  fun saveUser() = testScope.runBlockingTest {
+    userDao.save(PreviewData.User.data.first())
+    userDao.findAll().test {
+      assertThat(awaitItem(), equalTo(PreviewData.User.data.first()))
+    }
+  }
+
+  @After
+  @Throws(IOException::class)
+  fun teardown() {
+    db.close()
+    Dispatchers.resetMain()
+    testDispatcher.cleanupTestCoroutines()
+  }
+}