Unit testing certain tasks are done in a process

Question

I have some Scala code that I wish to unit test using ScalaMock:

class CancellationManagerSpec extends FlatSpec with MockFactory {

  "Cancelling a shipment" should "check shipment is not already shipped" in {

    val manager = mock[CancellationsManager]
    (manager.checkStatus _).expects(*, *).returning(true).once()

    val request = CancellationRequestedEvent("shipmentNumber")
    manager.processCancellation(request)
  }
}

The test fails:

[info] - should complete a series of tasks in happy case *** FAILED ***
[info]   Unexpected call: <mock-6> CancellationsManager.processCancellation(CancellationRequestedEvent(shipmentNumber))
[info]   
[info]   Expected:
[info]   inAnyOrder {
[info]     <mock-6> CancellationsManager.checkStatus(*, *) once (never called - UNSATISFIED)
[info]   }
[info]   
[info]   Actual:
[info]     <mock-6> CancellationsManager.processCancellation(CancellationRequestedEvent(shipmentNumber)) (Option.scala:121)

I want to test that when I process a cancellation, certain tasks are done. More generally, there is logic such as this that I would like to test:

class SalesOrderShippedProcess {
  def execute(salesOrder: SalesOrder): Unit = {
    if (doTask1() && doTask2()) {
      doTask3()
      doTask4()
      doTask5()
    }
  }

  def doTask1(): Boolean = ???
  def doTask2(): Boolean = ???
  def doTask3(): Boolean = ???
  def doTask4(): Boolean = ???
  def doTask5(): Boolean = ???
}

Where for some process, I want to check task 3, 4, and 5 are done only if task 1 and 2 is successful, and even if task 3 fails, task 4 and 5 should execute regardless.

What's the best way to test this? Is it failing because I'm calling a method of the mocked object directly? Do I need to move all the task methods to its own class then mock it, which seems a little strange to me just to be able to write a test for it?

Answer 1

Yes, you're doing this wrong - you should be calling a method on the real object (i.e. CancellationsManager in your case), not on the mock. So your test would look a bit like:

it should "check the status when an order is cancelled" in {
  val manager = new CancellationManager();
  val request = new CancellationRequestedEvent("shipmentId");

  manager.processCancellation(request);

  (manager.checkStatus _).expects(*, *).returning(true).once()
}

Mocks are there to replace the dependencies of the object being tested, not the object itself - for example, if your CancellationManager depended on an ShipmentFinder, you would mock out the ShipmentFinder so that you are testing only the CancellationManager code, not all its dependencies as well.