saving and retrieving data is working and db files are generated

build.gradle

@@ -78,6 +78,7 @@ dependencies {
     testImplementation "junit:junit:4.12"
     androidTestImplementation "androidx.test:runner:1.1.0"
     androidTestImplementation "androidx.test.espresso:espresso-core:3.1.0"
+    androidTestImplementation "androidx.test:core:1.0.0"
     androidTestImplementation "androidx.arch.core:core-testing:${versions.architectureComponents}"
 }
 

src/androidTest/java/cash/z/wallet/sdk/db/DbIntegrationTest.kt

@@ -0,0 +1,46 @@
+package cash.z.wallet.sdk.db
+
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import cash.z.wallet.sdk.dao.CompactBlockDao
+import cash.z.wallet.sdk.vo.CompactBlock
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+
+class DbIntegrationTest {
+    @get:Rule
+    var instantTaskExecutorRule = InstantTaskExecutorRule()
+
+    private var dao: CompactBlockDao? = null
+    private var db: CompactBlockDb? = null
+
+    @Before
+    fun initDb() {
+        // create real DB to inspect
+        db = Room
+            .databaseBuilder(ApplicationProvider.getApplicationContext(), CompactBlockDb::class.java, "compact-block.db")
+            .fallbackToDestructiveMigration()
+            .build()
+            .apply { dao = complactBlockDao() }
+    }
+
+    @Test
+    fun testDbExists() {
+        assertNotNull(db)
+    }
+
+    @Test
+    fun testDaoExists() {
+        assertNotNull(dao)
+        dao?.insert(CompactBlock(21))
+        dao?.insert(CompactBlock(18))
+
+        val block = dao?.findById(18)
+        assertNotNull(block)
+        assertEquals(18, block?.height)
+    }
+}

src/main/java/cash/z/wallet/sdk/dao/CompactBlockDao.kt

@@ -13,5 +13,5 @@ interface CompactBlockDao {
     fun insert(block: CompactBlock)
 
     @Query("SELECT * FROM CompactBlock WHERE height = :height")
-    fun findById(height: Int): LiveData<CompactBlock>
+    fun findById(height: Int): CompactBlock
 }