Question

Hello I am struggling with simple problem.

General idea:

class Foo(){
  public boolean method1();
  public String method2();
  public String method3();
  public String shortcut(){
    return (method1() == true) ? method2() : method3();
  }
}

How should I test shortcut method?

I know how to mock objects and test methods that use other object. Sample:

class Car{
  public boolean start(){};
  public boolean stop(){};
  public boolean drive(int km){};
}
class CarAutoPilot(){
  public boolean hasGotExternalDevicesAttached(){
     //Hardware specific func and api calls
     //check if gps is available 
     //check if speaker is on
     //check if display is on 
  }
  public boolean drive(Car car, int km){
    //drive
    boolean found = hasGotExternalDevicesAttached();
    boolean start = c.start();
    boolean drive = c.drive(km);
    boolean stop = c.stop();
    return (found && start && drive && stop) == true;   
  }
}

class CarAutoPilotTest(){
   @Test
   public void shouldDriveTenKm(){
     Car carMock = EasyMock.Create(Car.class);
     EasyMock.expect(carMock.start()).andReturns(true);
     EasyMock.expect(carMock.drive()).andReturns(true);
     EasyMock.expect(carMock.stop()).andReturns(true);
     EasyMock.reply(carMock);     

     CarAutoPilot cap = new CarAutoPilot();
     boolean result = cap.drive(cap,10);
     Assert.assertTrue(result);
     EasyMock.verify(carMock);
   }
}

But what about hasGotExternalDevicesAttached() method? This is only sample not real scenario. How should I test drive method? Should I also mock hasGotExternalDevicesAttached function?

Can I mock class that is being tested?

Answer 1

You can create a subclass of CarAutoPilot in which you override hasGotExternalDevicesAttached(), and run the test with an instance of this subclass.

You can do it inline:

CarAutoPilot cap = new CarAutoPilot() {
    public boolean hasGotExternalDevicesAttached(){
        // return true or false depending on what you want to test
    }
};

This way you can create a valid unit test for the rest of CarAutoPilot‘s behaviour.

You can call this a poor man’s partial mock if you wish 🙂