Full disclosure: I'm very new to mocking and mocking frameworks. I'm trying to use ScalaMock because it seemed like the 'default' mocking framework to use with ScalaTest but I am happy to use any other framework which is compatible with ScalaTest.
The problem: I've written in Scala a class that talks to a socket. The class has a type parameter of what sort of socket it is to talk to and one of it's arguments is a factory for creating sockets of that type. It has the signature:
class XScanner[T <: SocketClient]( confPath: String = "/etc/default/configPath", socketClientFactory: String => T ) extends ScannerBase(path)
I would like to be able to write unit tests for this class by supplying a mock SocketClient so my test code doesn't have to connect to a real socket but I can't work out how to do this with ScalaMock.
My test code looks like this:
val t = new XScanner[SocketClient](confPath, (s: String) => mock[SocketClient])
Clearly that won't compile because SocketClient expects a path to the socket as an argument but I can't call mock[SocketClient(s)] because that's not a type and I can't call mock[SocketClient](s) because mock doesn't take the arguments of the type passed to it as it's own arguments.
So how can I write a mock SocketClient factory to pass to my Scanner? I can't even work out how to mock a class that takes arguments!
The insight is that what you need to mock is socketClientFactory. And then set it up to return a mock SocketClient.
Given:
trait SocketClient { def frobnicate(): Unit } class ScannerBase(path: String) class XScanner[T <: SocketClient]( confPath: String = "/etc/default/configPath", socketClientFactory: String => T ) extends ScannerBase(confPath) { val socket = socketClientFactory("Some Socket Name") socket.frobnicate }
(side note - your default value for confPath can never be used because there's no default value for socketClientFactory).
then this should get you started (this is with Scala 2.9.x and ScalaMock2 - 2.10.x with ScalaMock3 will be slightly different, but not much so):
import org.scalatest.FunSuite import org.scalamock.scalatest.MockFactory import org.scalamock.generated.GeneratedMockFactory class ScannerTest extends FunSuite with MockFactory with GeneratedMockFactory { test("scanner") { val mockFactory = mockFunction[String, SocketClient] val mockClient = mock[SocketClient] mockFactory.expects("Some Socket Name").returning(mockClient) mockClient.expects.frobnicate val scanner = new XScanner("path/to/config", mockFactory) } }
For completeness, here's the same test in Scala 2.10.0 and ScalaMock3:
import org.scalatest.FunSuite import org.scalamock.scalatest.MockFactory class ScannerTest extends FunSuite with MockFactory { test("scanner") { val mockFactory = mockFunction[String, SocketClient] val mockClient = mock[SocketClient] mockFactory.expects("Some Socket Name").returning(mockClient) (mockClient.frobnicate _).expects() val scanner = new XScanner("path/to/config", mockFactory) } }
