scala mockito error `value thenReturn is not a member of Nothing`

[true-eye]

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I am new to Mockito so this may be a simple issue but I couldn't find a solution

  val users = List(User(name = "A"))
  val userRepoMock = mock[UserRepo]

  "GET /users" should {
    "return the users" in {
      when(userRepoMock.get()).thenReturn(Future.successful(Good(users)))

When I run the test, it fails as follows

   value thenReturn is not a member of Nothing
   [error]      L55:      
   when(userRepoMock.get()).thenReturn(Future.successful(Good(users)))
   [error]      L55:   

Here is the definition of UserRepo

trait UserRepo {
  def get(): Future[List[User]]
}

object UserRepo {

  class ActorImpl @Inject()(actor: UserSyncActor.Ref) extends UserRepo {
    override def get(): Future[List[User]] = {
      implicit val timeout: Timeout = 10.seconds
      actor.ref.ask(UserSyncActor.GetUsers).mapTo[List[User]]
    }
  }
}

versions:
Mockito ( mockito-core: 3.3.3, mockito-scala_2.12 )
os ( MacOS )

Could anyone can help me to fix this issue, please?
Thanks in advance

[dwijnand]

The issue is you're returning a Future[Good[List[User]]] not a Future[List[User]].