如何通过插入和测试数据正确进行 Room 迁移测试？

Question

I'm trying to test Room DB after including a new Column date . But I'm not getting how to insert data as I cannot use context in Testing.java file.

my code looks like this,

@RunWith(AndroidJUnit4.class)
public class MigrationTest {
    private static final String TEST_DB = "note_database";

    @Rule
    public MigrationTestHelper helper;

    public MigrationTest() {
        helper = new MigrationTestHelper(InstrumentationRegistry.getInstrumentation(),
                NoteDatabase.class.getCanonicalName(),
                new FrameworkSQLiteOpenHelperFactory());
    }

    @Test
    public void migrateAll() throws IOException {
        // Create earliest version of the database.

        SupportSQLiteDatabase db = helper.createDatabase(TEST_DB, 2);
        db.execSQL("INSERT INTO note_table (title,description,priority,date)" +
                " VALUES ('title_test','description_test','priority_test','10/12/2019');  ");
        db.close();


        // Open latest version of the database. Room will validate the schema
        // once all migrations execute.
        NoteDatabase appDb = Room.databaseBuilder(
                InstrumentationRegistry.getInstrumentation().getTargetContext(),
                NoteDatabase.class,
                TEST_DB)
                .addMigrations(ALL_MIGRATIONS).build();
        appDb.getOpenHelper().getWritableDatabase();
        appDb.close();
    }

    // Array of all migrations
    private static final Migration[] ALL_MIGRATIONS = new Migration[]{
            MIGRATION_1_2};
}

This code was working fine but , look at this reference code. i need to do something like this. and I'm not getting how to read getMigratedRoomDatabase data. can anyone help me on this.

// MigrationTestHelper automatically verifies the schema  
    //changes, but not the data validity
    // Validate that the data was migrated properly.
    User dbUser = getMigratedRoomDatabase().userDao().getUser();
    assertEquals(dbUser.getId(), USER.getId());
    assertEquals(dbUser.getUserName(), USER.getUserName());
    // The date was missing in version 2, so it should be null in 
    //version 3
    assertEquals(dbUser.getDate(), null);

Answer 1

That is nothing but appDb in your code. it will look like

appDb.userDao().getUser();