iphone - Unit Testing in Xcode, does it run the app?

Question

I'm running into a strange problem that I haven't run into before.

When you do cmd+U to run your Unit Tests (OCUnit for example) does it actually call the main.m, new up the appDelegate and run the app as if your had pressed cmd+R?

I only ask because I'm using CoreData behind this DataLayer. I'm mocking out the DataLayer successfully in my tests, but once I implemented a getAll method that is actually calling CoreData, the app/xcode is throwing an exception about the managed object model can't be nil. Which I understand, but I'm not meaning to actually new up the DataLayer class, and I've put a break point in my mainviewcontroller loadView method where it is calling the DataLayer getAll method. It shouldn't matter with tests because this is a mock object, but it's apparently calling the real instance.

So back to my question, when pressing cmd+U does it also run the app first then run the tests?

Answer 1

The application is actually run but there is a trick you can use to prevent it from running.

int main(int argc, char* argv[]) {
    int returnValue;

    @autoreleasepool {
        BOOL inTests = (NSClassFromString(@"SenTestCase") != nil
                     || NSClassFromString(@"XCTest") != nil);    

        if (inTests) {
            //use a special empty delegate when we are inside the tests
            returnValue = UIApplicationMain(argc, argv, nil, @"TestsAppDelegate");
        }
        else {
            //use the normal delegate 
            returnValue = UIApplicationMain(argc, argv, nil, @"AppDelegate");
        }
    }

    return returnValue;
}