Hello, I have a mocked object and trying to setup `coEvery` to mock a specific function although som...

# mockk

[André Martins]

Hello, I have a mocked object and trying to setup coEvery to mock a specific function although somehow the coEvery call is hanging when I run the test. What can cause this hanging?

[Mattia Tommasone]

is the function you are mocking suspend?

[André Martins]

Think I’ve found the problem, it was due to mocking it twice

[Mattia Tommasone]

do you have a full reproducible example? I’d like to take a look

[André Martins]

I’m mocking a CoroutineCollection from KMongo and using this function that I’ve came up with to do it regarding this

inline fun <reified T : Any> mockkCoroutineCollection(
    name: String? = null,
    relaxed: Boolean = false,
    vararg moreInterfaces: KClass<*>,
    relaxUnitFun: Boolean = false,
    block: MongoCollection<T>.() -> Unit = {}
): MongoCollection<T> = mockk(name, relaxed, *moreInterfaces, relaxUnitFun = relaxUnitFun) {
    mockkStatic(MongoCollection<T>::coroutine)
    val that = this
    every { coroutine } returns mockk(name, relaxed, *moreInterfaces, relaxUnitFun = relaxUnitFun) {
        every { collection } returns that
    }
    block()
}

And I have a service which receives the database and obtains both collections and seems that from the order I call it the mock doesn’t capture type information

[André Martins]

Now trying to figure it out if I can return the respective collection for the specified type

[André Martins]

Some more context here

data class User(val id: Int, val name: String)
data class Book(val id: Int, val name: String)

class Service(private val myDatabase: CoroutineDatabase) {
    private val userCollection: CoroutineCollection<User> = myDatabase.getCollection("users")
    private val booksCollection: CoroutineCollection<Book> = myDatabase.getCollection("books")

    fun getUserById(id: Int): User? = userCollection.findOneById(id)
    fun getBookById(id: Int): Book? = booksCollection.findOneById(id)
    // ...
}

fun test() {
    val mongoDatabase = mockkCoroutineDatabase(relaxed = true)
    val usersCollection = mockkCoroutineCollection<User>(relaxed = true)
    val booksCollection = mockkCoroutineCollection<Book>(relaxed = true)
    val coroutineUsers: CoroutineCollection<User> = usersCollection.coroutine
    val coroutineBooks: CoroutineCollection<Book> = booksCollection.coroutine

    every {
        mongoDatabase.getCollection(any(), User::class.java)
    } returns usersCollection

    every {
        mongoDatabase.getCollection(any(), Book::class.java)
    } returns booksCollection

    val sut: Service = Service(mongoDatabase)
    

    val expectedUser = User(20, "Joe")

    // depending on the order I create the mocked collections this hangs or not
    coEvery {
        coroutineUsers.findOneById(any())
    } returns expectedUser

    assertEquals(expectedUser, sut.getUserById(20))
}

[André Martins]

Basically if I switch the two lines that call mockkCoroutineCollection this will pass

[André Martins]

@Mattia Tommasone any ideias? 😅

[Mattia Tommasone]

not many ideas on how to solve it, but i’m guessing the issue is with the fact that MongoCollection<T>::coroutine is static, so mockkStatic-ing it more than once leads to recorded calls being erased

[André Martins]

the thing is the every { coroutine } returns … doesn’t capture type information

[André Martins]

Think I figured it out

[André Martins]

just did every { ofType<MongoCollection<T>>().coroutine } returns …

[Mattia Tommasone]

ah nice, that makes sense

[André Martins]

binding the type to the mock

[André Martins]

guess it was doing any().coroutine