CODEWITHSUNDEEP
scalaunit-testingmockitoscalatest
Saturnian
Saturnian

Reputation: 1948

thenReturn overloaded method has alternatives - how can this be resolved?

I have a function within a class like:

def saveToken(token: Token, ttl: Instant, client: Client, partner: Partner, info: Info): Future[EitherErrorsOr[Done]]

and EitherErrorsOr is :

type EitherErrorsOr[A] = scala.Either[Errors, A]

Errors is our internal Errors class

When I try to mock saveToken as follows:

when(
      mockService.saveToken(
        any(), any(), any(), any(), any()
    )
  ).thenReturn(Right(NoOpVal).toFut)

then I get an error such as:

overloaded method value thenReturn with alternatives:
  (x$1: scala.concurrent.Future[EitherErrorsOr[Done]],x$2: scala.concurrent.Future[EitherErrorsOr[Done]]*)org.mockito.stubbing.OngoingStubbing[scala.concurrent.Future[EitherErrorsOr[Done]]] <and>
  (x$1: scala.concurrent.Future[EitherErrorsOr[Done]])org.mockito.stubbing.OngoingStubbing[scala.concurrent.Future[EitherErrorsOr[Done]]]
 cannot be applied to (scala.concurrent.Future[scala.util.Right[Nothing,NoOp]])
      ).thenReturn(Right(NoOpVal).toFut)

Why does thenReturn come up with so many alternatives?

Note: Done is our internal class that signifies that an operation is complete , toFut converts to a Future object, NoOpVal is just some type created for testing purposes

Upvotes: 1

Views: 1033

Answers (1)

Tomer Shetah
Tomer Shetah

Reputation: 8539

The issue you are having is in the return type. The return type of the method is Future[EitherErrorsOr[Done]], which is Future[Either[Errors, Done]].

Let's now analyze the type of Right(NoOpVal).toFut. The implementation of Right is:

final case class Right[+A, +B](b: B) extends Either[A, B] {
  def isLeft = false
  def isRight = true
}

Let's assume that NoOpVal is of type A, when calling Right(NoOpVal) you get an instance of type Right[Nothing, A], because you didn't supply the first generics to Right.

Right[Nothing, A] cannot be casted into Future[EitherErrorsOr[Done]].

How do you solve that? Easy just do:

when(mockService.saveToken(any(), any(), any(), any(), any()))
    .thenReturn(Right[Errors, Done](NoOpVal).toFut)

and make sure NoOpVal extends Done.

Upvotes: 2

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