How to mock a Scala singleton object?

Question

I am trying to mock a Scala singleton object. In particular, I need to mock the object play.api.libs.ws.WS used inside a service component (class under test). U

Answer 1

Don't mock the singleton. Instead of WS, make your service component depend on a thin facade hiding it:

trait GeolocationService {
  def ws: (String, Seq[String]) => Promise[Response] = { (url, params) =>
    wsClient.url(serviceProviderEndpoint.get).withQueryString(params: _*).get()
  }
  def getPath(origin: Location, destination: Location): Future[Route]
}

and in your test, just override ws method with a mock, which is now easy to create:

val mockedWs = mock[(String, Seq[String]) => Promise[Response]]
// TODO specify mock's behavior here
val service = new DefaultGeolocationService() {
  override def ws = mockedWs
}