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I am using a third party framework to send data to a server. I am mocking that third party framework to isolate and test how my code interacts with it. This is to avoid to avoid waiting to get back data from the network while unit testing, and because I want to test the error handling code that I've written.

I am not using OCMock or anything like it, I am writing my own mock object by subclassing the 3rd party framework.

My method looks like this-

- (void)loginWithCredentials:(NSDictionary *)credentials
{
    NSDictionary *credentials = [self credentials];
    NSString *username = [credentials objectForKey:kUserCredintialUsername];
    NSString *password = [credentials objectForKey:kUserCredintialPassword];

    [ThirdPartyClass loginWithUsername:username 
                           andPassword:password 
                                 block:^(ThirdPartyClass *user, NSError *error){
    if (user) {
        NSLog(@"We logged in");
    }
    else if (error) {
        NSLog(@"%@", [error errorString]);
    }
}];
}

What I'd like to do is to is to call loginWithUsername:andPassword:block: on my mock in my unit tests. The current method is, obviously, untestable because it doesn't follow "tell, don't ask" (I'm not telling loginWithCredentials: which class to call loginWithUser...block: on). The only way that I can think to solve this is to add a class variable to my instance or class or add an argument to loginWithCredentials: so I can substitute my mock in. The production code doesn't gain any clarity by doing so - it is already being written as an adapter to the 3rd party library. Instead, I would prefer to try to refactor the loginWithCredentials: method.

Nat Osten
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    You can swizzle class methods to replace `loginWithUsername:andPassword:block:` with a stub or fake (i.e. http://stackoverflow.com/questions/3267506/how-to-swizzle-a-class-method-on-ios). Is there any reason you don't want to use testing libraries which can provide this behavior? I'm a fan of https://github.com/allending/Kiwi which would allow you to write statements like `[[[ThirdPartClass] should] receive:@selector(loginWithUsername:andPassword:block:) andReturn:mockObject]`. I find that much easier than manually swizzling methods, especially since I then don't have to undo the swizzle. – Jonah Sep 12 '12 at 20:55
  • I had considered swizzling but it seems rather fragile and I'm concerned that if it's not done right I might get false confirmation of my unit tests passing. The problem also gave off a code smell that I might be going about writing my method in a less than ideal way. As for the testing libraries, I am just trying to avoid accommodating another third party library into my code. – Nat Osten Sep 12 '12 at 21:10

1 Answers1

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There is an HTTP stubbing library at https://github.com/AliSoftware/OHHTTPStubs. It works by catching outgoing requests and returning file data. It also allows rudimentary simulation of loading speeds for different types of networks.

James Stewart
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