Repository testing with fakes in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a fake repository class implementing the UserRepository interface.

Android Kotlin

class FakeUserRepository : UserRepository {
    override fun getUser(id: Int): User {
        return [1]
    }
}

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

AUser()

Bnull

Cthrow Exception("Not implemented")

DUser(id, "Fake User")

Attempts:

3 left

💡 Hint

Common Mistakes

Returning null instead of a User object.

Throwing an exception instead of returning a fake user.

The fake repository returns a dummy User object with the given id and a fixed name.

2fill in blank

medium

Complete the test function to verify the fake repository returns the expected user name.

Android Kotlin

fun testGetUserReturnsFake() {
    val repo = FakeUserRepository()
    val user = repo.getUser(1)
    assert(user.name == [1])
}

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

A"Real User"

B"Test User"

C"Fake User"

D"Unknown"

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong expected name in the assertion.

Confusing the fake user name with a real user name.

The fake repository returns a user with the name "Fake User" as defined in the fake.

3fill in blank

hard

Fix the error in the fake repository to store users in a mutable map and return them by id.

Android Kotlin

class FakeUserRepository : UserRepository {
    private val users = mutableMapOf<Int, User>()

    fun addUser(user: User) {
        users[[1]] = user
    }

    override fun getUser(id: Int): User? {
        return users[[2]]
    }
}

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

Auser.id

Buser.name

Cid

Duser

Attempts:

3 left

💡 Hint

Common Mistakes

Using user.name as the key instead of user.id.

Using user instead of id to retrieve from the map.

The addUser function uses user.id as the key to store the user. The getUser function uses the id parameter to retrieve the user.

4fill in blank

hard

Fill both blanks to complete the test that adds a user to the fake repository and verifies retrieval.

Android Kotlin

fun testAddAndGetUser() {
    val repo = FakeUserRepository()
    val user = User(10, "Test User")
    repo.[1](user)
    val retrieved = repo.[2](10)
    assert(retrieved?.name == "Test User")
}

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

AaddUser

BgetUser

CremoveUser

DupdateUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using removeUser or updateUser instead of addUser or getUser.

Mixing up the order of method calls.

The test calls addUser to add the user, then getUser to retrieve it by id.

5fill in blank

hard

Fill all three blanks to create a fake repository with a mutable list and implement add, get, and clear methods.

Android Kotlin

class FakeUserRepository : UserRepository {
    private val users = mutableListOf<User>()

    fun [1](user: User) {
        users.[2](user)
    }

    fun [3]() {
        users.clear()
    }

    override fun getUser(id: Int): User? {
        return users.find { it.id == id }
    }
}

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

AaddUser

Badd

CclearUsers

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect method names that don't match the calls.

Calling wrong list methods like remove instead of add.

The method to add a user is named addUser, which calls the list's add method. The method to clear users is named clear, which calls users.clear().