Test-Driven Development in Android

To create our first test we’ll also need two properties. We’ll need our database access object:

private val wishlistDao: WishlistDao =
    Mockito.spy(WishlistDaoImpl())
private val viewModel =
    DetailViewModel(RepositoryImpl(wishlistDao))

First you created a spy for the WishlistDao object which in turn we’re going to use to create our repositoryImpl.

Now we’re ready to create our first integration tests. Remember we’re doing test driven development, which means we need to create a test, see it fail and then make it pass. So, add a few spaces here and type:

@Test
fun saveNewItemCallsDatabase() {
  viewModel.saveNewItem(Wishlist("Victoria",
      listOf("RW Android Apprentice Book", "Android phone"), 1),
      "Smart watch")

  verify(wishlistDao).save(any())
}

Now, execute your test and see it fail. Remember that you’ll need an emulator running or roboelectric.

As expected the tests failed because we wanted to see a call to the save method of our wishlistdao but it was never called. So, open your DetailViewModel class and add the following line to saveNewItem:

repository.saveWishlistItem("", listOf())

Execute your tests and see it pass.

Nice!