Mockito Scala NullPointerException

Question

I am having troubles getting my first Mock working in my Chat application using Mockito, I am trying to mock a Repository that takes a user ID as a string and returns all the conversations for this user. I am having a very hard time getting rid of a NullPointerException

Here is my Repository trait:

trait UserRepository {
  val getConversations: (String) => Option[Vector[User]]
}

Here is my Service:

class UserService(userRepository: UserRepository){
  private val boolToNumber : (Boolean) => Int = (bool) => ... not useful here
  private val countToBool : (Int) => Boolean = (int) => ... not useful here

  val getParticipations: (String) => Option[Vector[User]] = (name) => {
    userRepository.getConversations(name) match {
    ... some implementation
  }
}

And my tests

  // init
  val userRepository = mock[UserRepository]

  // setup
  when(userRepository.getConversations("Smith")) thenReturn (
    Some(
      Vector(
        User("Smith", true, true, ConversationKey("Smith", "Smith and O'Connell chatroom")),
        User("Smith", false, true, ConversationKey("Smith", "Smith and O'Connell chatroom"))
      )
    )
  )
  val userService : UserService = new UserService(userRepository)
  // run
  val actual = userService.getParticipations("Smith")

  // verify
  actual mustBe Vector(User("Smith", false, true, ConversationKey("Smith", "Smith and O'Connell chatroom")))

What I have tried so far:

printing after each operation in the tests, printing UserRepository returns Mock for UserRepository, hashCode: 1319190020, but the UserService is not printing so it is the one throwing the NullPointerException
changing "Smith" by the matcher any[String], same error, and anyString same error
Wrapping String in a class called StringValue, same error Mockito matchers

That solved it!! Thank you, do you have any idea why it would cause a NullPointerException? EDIT: Can you answer (not with a comment) so I can accept your answer? — Daniel, May 28 '17 at 14:51
@Daniel, can you please update your example to add how you created test class and maven or sbt dependency. I cannot get how you mock with Mockito using the following syntax: val userRepository = mock[UserRepository]. — Alexandr, Jun 25 '18 at 07:46

score 1 · Accepted Answer · answered May 28 '17 at 22:58

1

Change your val functions to def functions.

Im not too sure exactly why this is, but mockito is a java library so im not surprised that it doesnt handle scala function values well where Def's compile to the same thing as java methods.

answered May 28 '17 at 22:58

Stephen

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Mockito Scala NullPointerException

1 Answers1