UserViewModelTestShould.kt

class UserViewModelTestShould{

    @get:Rule
    val rule = InstantTaskExecutorRule()

    private lateinit var viewModel: UserViewModel
    @Mock lateinit var repository: UserRepository
    @Mock lateinit var observer: Observer<UserViewModel.DisplayData>

    @Before
    fun setUp(){
        MockitoAnnotations.initMocks(this)
        viewModel = UserViewModel(repository)
        viewModel.getData().observeForever(observer)
    }

    @Test
     fun `test user data retrieved successfully`() = runBlockingTest{
        val username = "pranay1494"
        val data = User().apply { name = "Pranay" }
        
        Mockito.`when`(repository.fetchRepository(username)).thenReturn(data)

        viewModel.fetchUserData(username)

        Mockito.verify(observer,times(1)).onChanged(any())
    }
}