UsingMockObjects

last edited May 13, 2008 21:56:20 (216.27.179.42)
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CocoaDiscussions - OCMock - how?I am interested in using OCMock but there is little documentation and I am unsure of how to begin. I have been using OCUnit successfully. The reason I think I need to use mock objects is that I am designing an object that will function in response to user input. I want the object (functioning as a controller) I am going to test to present some choice to the user, then respond to the user's choice by manipulating model objects. I want to be able to tell the object what the user's choices were and then test what it will do based on these choices. I think I need a MockObject to substitute for the view object.Can anyone point me to a useful tutorial or at least post a few hints?
Martin Fowler has a very good article on Mock Objects here:http://www.martinfowler.com/articles/mocksArentStubs.html Basically, you're right - if you want to test that a controller properly interacts with a view - without actually using the view, than Mock Objects are a good way to go.--TimHart!
Original Poster (or anybody else): Have you had success? Anybody care to write up a brief HOWTO for OCMock? I'm in the same boat. Or, how about a more concrete question: I'm trying to mock an object that is a delegate for another object, to make sure that the appropriate messages get passed to the delegate. I have an informal protocol in the object that sends the delegate messages (the protocol is on NSObject). I don't have any classes that "implement" this informal protocol - that's for people who use my framework to do. So how can I create a mock object that responds to the message? When I try something like: 
  // I've declared an informal protocol in MYObject.h on NSObject, called MYInformalProtocol
  MYObject *mo = [[MYObject alloc] init];
  OCMockObject *delegateMock = [OCMockObject MYInformalProtocol];

  [mo setDelegate:delegateMock];
  [[delegateMock expect] myDelegateMessage:mo];

  [mo myMessage];

  [delegateMock verify];
I get an error: error: -[MYTestTarget? myTestName]: *** -[NSProxy methodSignatureForSelector:] called!. I assume that this is because MYObject? checks whether its delegate responds to myDelegateMessage before sending the message. Is there a good way to do this? Do I need to create a formal protocol for classes to use as a delegate??
A request for OCMock (posted here, because I don't see any way to contact the author on OCMock's site): allow andReturn: (or some similar method) to return BOOL values. NO works (by chance, because 0=NO=nil), but YES doesn't work. Generally, it would be useful to andReturn:YES, and specifically when I'm using delegates. I cannot mock a delegate object because the code checks whether or not the delegate respondsToSelector:, which needs to return YES, which I can't do in my mock object. So I can't test code that has delegates with OCMock (at least not test whether they properly call the delegate).
Values such as YES are supported but you have to specify them with OCMOCK_VALUE, eg. [[[myMock expect] andReturn:OCMOCK_VALUE(YES)] foo]
Actually, that won't quite work. You cannot pass something other than a variable into OCMOCK_VALUE. So the boolean would have to look like this: 
BOOL no = NO;
[[[myMock expect] andReturn:OCMOCK_VALUE(no)] haveYouGotAnyLimburger];
To the above poster, you have to get the mock object as follows: 
OCMockObject *delegateMock = [OCMockObject mockForClass:[NSObject class]];
The OCMock homepage at Mulle Kybernetik now has a how-to and contact details, even a mailing list.