CODEWITHSUNDEEP
scalaunit-testingmocking
Dani
Dani

Reputation: 1022

Scala unit testing - stubbing a singleton

I'm new to unit testing in Scala and I can't find a way to stub a function defined in a singleton object.

For example:

class Profile {
  def getLatest
    ...
    Feed.getLatestEntries
    ...
}

object Feed {
  def getLatestEntries: Future[List[FeedEntry]] { /* Access some API*/ }
}

I'm trying to unit test the getLatest function defined in the Profile class. Since I don't want to actually access an external API through the web in my unit tests I'm trying to stub the Feed object and its getLatestEntries function to return some predefined value.

I've looked into the ScalaMock, EasyMock and Mockito frameworks but could not find a way to stub a method of a singleton object. ScalaMock states

How come all the mocking frameworks do not offer this functionality? How can I do this? stub Feed.getLatestEntries ?

Thanks

Upvotes: 1

Views: 2801

Answers (1)

Arne Claassen
Arne Claassen

Reputation: 14404

My approach has been to create the logic of the singleton as a trait and then have the object extend the trait. This allows me provide the Singleton as a default or implicit argument, but provide a stubbed out implementation for testing

trait FeedLogic {
  def getLatestEntries: Future[List[FeedEntry]] { /* Access some API*/ }
}

object Feed extends FeedLogic

def somethingWantingFeed(...)(feed: FeeLogic = Feed) = { ??? }

Upvotes: 5

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