aNonNull unexpected behaviour

[Jan Kodet]

I've probably misinterpreted something, but here goes....

Using the State pattern (see e.g. http://exciton.cs.rice.edu/JavaResources/DesignPatterns/StatePat.htm) I want to test the logic in my states. So I have two interfaces: State and Context. Interface Context defines the method setState(State newState) and interface State defines some event handling methods. The interfaces are then implemented by the classes I want to test.

My test methods look something like (using version 2.4.0):

    @Test
    public void testOnEvent() {
        // Class under test
        StateOne stateOne = new StateOne(mockContext);

        context.checking(new Expectations() {
                {
                    // We should transit to StateTwo
                    one(mockContext).setState(with(aNonNull(StateTwo.class)));
                }
        });

        stateOne.onEvent(new SomeEvent());
        context.assertIsSatisfied();
    }


To my delight, the test succeeds. My joy was somewhat dimmed when I noted that I can put any state I like as argument to aNonNull(), as long as it implements State. They all fullfill the expectation.

This was not what I'd expect. I hoped that "with(aNonNull(StateTwo.class))" would ensure that I go to the right state, not just that the argument has the correct interface.

I assume that I've got something wrong, but hope for any pointers to how I should do my tests to ensure that I really go to StateTwo.

Cheers,

/JMK

[Steve Freeman-2]

Try

   one(context).setState(with(instanceOf(StateTwo.class));

which should be more precise. Look at the static methods on the  
hamcrest Matchers class for more options.

Give all the collaboration going on, I'd make a point of writing some  
integration tests to make sure this all hangs together.

S.


On 4 Jun 2008, at 12:04, Jan Kodet wrote:

>
> I've probably misinterpreted something, but here goes....
>
> Using the State pattern (see e.g.
> http://exciton.cs.rice.edu/JavaResources/DesignPatterns/ 
> StatePat.htm) I want
> to test the logic in my states. So I have two interfaces: State and  
> Context.
> Interface Context defines the method setState(State newState) and  
> interface
> State defines some event handling methods. The interfaces are then
> implemented by the classes I want to test.
>
> My test methods look something like (using version 2.4.0):
>
>    @Test
>    public void testOnEvent() {
>        // Class under test
>        StateOne stateOne = new StateOne(mockContext);
>
>        context.checking(new Expectations() {
>                {
>                    // We should transit to StateTwo
>
> one(mockContext).setState(with(aNonNull(StateTwo.class)));
>                }
>        });
>
>        stateOne.onEvent(new SomeEvent());
>        context.assertIsSatisfied();
>    }
>
>
> To my delight, the test succeeds. My joy was somewhat dimmed when I  
> noted
> that I can put any state I like as argument to aNonNull(), as long  
> as it
> implements State. They all fullfill the expectation.
>
> This was not what I'd expect. I hoped that  
> "with(aNonNull(StateTwo.class))"
> would ensure that I go to the right state, not just that the  
> argument has
> the correct interface.
>
> I assume that I've got something wrong, but hope for any pointers to  
> how I
> should do my tests to ensure that I really go to StateTwo.
>

Steve Freeman
Winner of the Agile Alliance Gordon Pask award 2006

http://www.m3p.co.uk

M3P Limited.
Registered office. 2 Church Street, Burnham, Bucks, SL1 7HZ.
Company registered in England & Wales. Number 03689627



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[Jan Kodet]

Well, it works, but since instanceOf returns Object, I have to cast it back to what I expected:

   one(context).setState((StateTwo)with(instanceOf(StateTwo.class));

This lacks the normal beauty of JMock, so my gut feeling tells me that there is something here that I've missed.

/JMK

Steve Freeman-2 wrote:

Try

   one(context).setState(with(instanceOf(StateTwo.class));

which should be more precise. Look at the static methods on the  
hamcrest Matchers class for more options.

Give all the collaboration going on, I'd make a point of writing some  
integration tests to make sure this all hangs together.

S.


On 4 Jun 2008, at 12:04, Jan Kodet wrote:

>
> I've probably misinterpreted something, but here goes....
>
> Using the State pattern (see e.g.
> http://exciton.cs.rice.edu/JavaResources/DesignPatterns/ 
> StatePat.htm) I want
> to test the logic in my states. So I have two interfaces: State and  
> Context.
> Interface Context defines the method setState(State newState) and  
> interface
> State defines some event handling methods. The interfaces are then
> implemented by the classes I want to test.
>
> My test methods look something like (using version 2.4.0):
>
>    @Test
>    public void testOnEvent() {
>        // Class under test
>        StateOne stateOne = new StateOne(mockContext);
>
>        context.checking(new Expectations() {
>                {
>                    // We should transit to StateTwo
>
> one(mockContext).setState(with(aNonNull(StateTwo.class)));
>                }
>        });
>
>        stateOne.onEvent(new SomeEvent());
>        context.assertIsSatisfied();
>    }
>
>
> To my delight, the test succeeds. My joy was somewhat dimmed when I  
> noted
> that I can put any state I like as argument to aNonNull(), as long  
> as it
> implements State. They all fullfill the expectation.
>
> This was not what I'd expect. I hoped that  
> "with(aNonNull(StateTwo.class))"
> would ensure that I go to the right state, not just that the  
> argument has
> the correct interface.
>
> I assume that I've got something wrong, but hope for any pointers to  
> how I
> should do my tests to ensure that I really go to StateTwo.
>

Steve Freeman
Winner of the Agile Alliance Gordon Pask award 2006

http://www.m3p.co.uk

M3P Limited.
Registered office. 2 Church Street, Burnham, Bucks, SL1 7HZ.
Company registered in England & Wales. Number 03689627



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[Steve Freeman-2]

I fear that's the best we can do given the mess that is Java generics.  
One kludge might be to write a little helper method in the test class  
that wraps up the cast.

one(context).setState(withA(StateTwo.class));

S.

On 5 Jun 2008, at 08:32, Jan Kodet wrote:

> Well, it works, but since instanceOf returns Object, I have to cast  
> it back
> to what I expected:
>
>   one(context).setState((StateTwo)with(instanceOf(StateTwo.class));
>
> This lacks the normal beauty of JMock, so my gut feeling tells me  
> that there
> is something here that I've missed.
>
> /JMK

Steve Freeman
Winner of the Agile Alliance Gordon Pask award 2006

http://www.m3p.co.uk

M3P Limited.
Registered office. 2 Church Street, Burnham, Bucks, SL1 7HZ.
Company registered in England & Wales. Number 03689627



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