ViewModel testing in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a ViewModel instance in a test.

Android Kotlin

val viewModel = [1]()

Drag options to blanks, or click blank then click option'

ALiveData

BMyViewModel

CViewModelProvider

DMutableLiveData

Attempts:

3 left

💡 Hint

Common Mistakes

Using ViewModelProvider in unit tests without Android framework.

Trying to instantiate LiveData instead of ViewModel.

You create an instance of your ViewModel class directly in tests to test its logic.

2fill in blank

medium

Complete the code to observe LiveData value changes in a test.

Android Kotlin

viewModel.data.observeForever [1]

Drag options to blanks, or click blank then click option'

A{ value -> println(value) }

B(value) -> println(value)

CObserver { value -> println(value) }

Dthis

Attempts:

3 left

💡 Hint

Common Mistakes

Using Observer class syntax instead of lambda.

Passing 'this' which is not a valid observer.

In tests, observeForever takes a lambda to react to LiveData changes.

3fill in blank

hard

Fix the error in the test code to get LiveData value synchronously.

Android Kotlin

val value = viewModel.data.[1]()

Drag options to blanks, or click blank then click option'

ApostValue

BgetValue

Cobserve

DgetOrAwaitValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using getValue which returns null if no value is set.

Using observe which requires a lifecycle owner.

getOrAwaitValue is a helper function to get LiveData value in tests synchronously.

4fill in blank

hard

Fill both blanks to mock a repository and inject it into ViewModel for testing.

Android Kotlin

val mockRepo = [1]()
val viewModel = MyViewModel([2])

Drag options to blanks, or click blank then click option'

Amockk

BmockRepo

Crepository

Dmock

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the class name instead of the mock instance.

Not using a mocking library to create the mock.

Use mockk() to create a mock repository, then pass it to ViewModel constructor.

5fill in blank

hard

Fill all three blanks to verify a repository method call in ViewModel test.

Android Kotlin

verify(exactly = [1]) { mockRepo.[2]([3]) }

Drag options to blanks, or click blank then click option'

A1

BfetchData

Cany()

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 for exactly means no calls expected.

Not using any() causes verification to fail if argument differs.

Verify that fetchData was called exactly once with any argument.