PartTests

Steps

• 1.1 - First ViewModel & LiveData with Weather Detail View
• 1.2 - ViewModel & Events with the Splash View
• 1.3 - Shared ViewModel between Activity/Fragments, with the Weather View

Writing unit tests for Android ViewModel

1.1 - DetailViewModelMockTest

Let's update the corresponding unit tests.

• Let's create the DetailViewModelMockTest from DetailPresenterMockTest
• Your mocked view is now an Android Observer (android.arch.lifecycle.Observer) of State:

@Mock
lateinit var view: Observer<ViewModelState>

• Rename your presenter property to viewModel and change its type to DetailViewModel

Let's update the before() function to setup your dependency:

• Also make the view observe the ViewModel with observeForever function: viewModel.states.observeForever(view)
• Uncomment the InstantTaskExecutorRule rule to allow LiveData execution in test

Now update the tests to check that view has been notified with an ArgumentCaptor:

// setup ArgumentCaptor
val arg = ArgumentCaptor.forClass(ViewModelState::class.java)
// Here we expect 2 calls on view.onChanged
verify(view, times(2)).onChanged(arg.capture())

val values = arg.allValues
// Test obtained values in order
assertEquals(2, values.size)
assertEquals(Loading, values[0])
assertEquals(DetailViewModel.DetailLoaded(weather), values[1])

1.2 - SplashViewModelMockTest

Update the corresponding tests in SplashViewModelMockTest.kt:

• Create SplashViewModelMockTest from SplashPresenterMockTest class
• Uncomment InstantTaskExecutorRule
• Rename presenter property to viewModel
• Change type of view property to Observer<ViewModelEvent>
• Update before() function to observe your viewModel
• Update the tests using ArgumentCaptor to check the returned events

1.3 - WeatherViewModelMockTest

Let's update our tests. From the WeatherHeaderPresenterMockTest class:

• Delete WeatherListPresenterMockTest
• Rename WeatherHeaderPresenterMockTest class to WeatherViewModelMockTest
• Rename presenter property to viewModel
• Change type of view property to Observer<ViewModelState>, and rename it statesView
• Add a new view, eventsView of type Observer<ViewModelEvent>
• Uncomment InstantTaskExecutorRule
• Update before() function to observe with statesView and eventsView
• Update the tests using ArgumentCaptor to check the returned states and events (look at the MockedData object which contains mocked data)