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; } 

Answer 2

Here's a variation of Sulthan's answer that uses XCTest, which is the default for test classes generated by XCode 5.

 int main(int argc, char * argv[]) {     @autoreleasepool {         BOOL runningTests = NSClassFromString(@"XCTestCase") != nil;         if(!runningTests)         {             return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));         }         else         {             return UIApplicationMain(argc, argv, nil, @"TestAppDelegate");         }     } } 

This goes into main.m, which should be under Supporting Files in a standard project layout.

Then in your tests directory add:

TestAppDelegate.h

 #import <Foundation/Foundation.h>  @interface TestAppDelegate : NSObject<UIApplicationDelegate> @end 

TestAppDelegate.m

 #import "TestAppDelegate.h"  @implementation TestAppDelegate @end