add database testing

app/src/androidTest/java/it/unisannio/ding/ids/wedroid/app/TestHelper.kt

@@ -0,0 +1,22 @@
+package it.unisannio.ding.ids.wedroid.app
+
+import androidx.lifecycle.*
+
+class OneTimeObserver<T>(private val handler: (T) -> Unit) : Observer<T>, LifecycleOwner {
+    private val lifecycle = LifecycleRegistry(this)
+    init {
+        lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_RESUME)
+    }
+
+    override fun getLifecycle(): Lifecycle = lifecycle
+
+    override fun onChanged(t: T) {
+        handler(t)
+        lifecycle.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY)
+    }
+}
+
+fun <T> LiveData<T>.observeOnce(onChangeHandler: (T) -> Unit) {
+    val observer = OneTimeObserver(handler = onChangeHandler)
+    observe(observer, observer)
+}

app/src/androidTest/java/it/unisannio/ding/ids/wedroid/app/data/dao/BoardDaoTest.kt

@@ -0,0 +1,103 @@
+package it.unisannio.ding.ids.wedroid.app.data.dao
+
+import android.content.Context
+import androidx.arch.core.executor.testing.InstantTaskExecutorRule
+import androidx.room.Room
+import androidx.test.core.app.ApplicationProvider
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import it.unisannio.ding.ids.wedroid.app.data.database.BoardDatabase
+import it.unisannio.ding.ids.wedroid.app.data.entity.Board
+import it.unisannio.ding.ids.wedroid.app.observeOnce
+import junit.framework.TestCase.assertEquals
+import kotlinx.coroutines.runBlocking
+import org.junit.After
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import java.io.IOException
+
+
+@RunWith(AndroidJUnit4::class)
+class BoardDaoTest {
+    private lateinit var dao: BoardDao
+    private lateinit var db: BoardDatabase
+
+    @get:Rule
+    val instantTaskExecutorRule = InstantTaskExecutorRule()
+
+    @Before
+    fun createDb() {
+        val context = ApplicationProvider.getApplicationContext<Context>()
+        db = Room.inMemoryDatabaseBuilder(
+            context, BoardDatabase::class.java
+        ).build()
+        dao = db.boardDao()
+    }
+
+    @After
+    @Throws(IOException::class)
+    fun closeDb() {
+        db.close()
+    }
+
+    @Test
+    fun emptyDatabaseOnCreation() {
+        dao.getAllBoard().observeOnce {
+            assertEquals(0, it.size)
+        }
+    }
+
+    @Test
+    fun insert() {
+        val board = Board("id", "title")
+
+        runBlocking {
+            dao.insert(board)
+        }
+
+        dao.getAllBoard().observeOnce {
+            assertEquals(1, it.size)
+            assertEquals(board, it[0])
+        }
+    }
+
+    fun getInAscendingOrder() {
+        val board0 = Board("id0", "title0")
+        val board1 = Board("id1", "title1")
+
+        runBlocking {
+            dao.insert(board1)
+        }
+
+        runBlocking {
+            dao.insert(board0)
+        }
+
+        dao.getAllBoard().observeOnce {
+            assertEquals(2, it.size)
+            assertEquals(board0, it[0])
+            assertEquals(board1, it[1])
+        }
+    }
+
+    fun delete() {
+        val board = Board("id", "title")
+
+        runBlocking {
+            dao.insert(board)
+        }
+
+        runBlocking {
+            dao.delete(board)
+        }
+
+        dao.getAllBoard().observeOnce {
+            assertEquals(0, it.size)
+        }
+    }
+}
+
+
+
+