CoreDataEquality.m

// Run this in the viewDidLoad of a new Core Data project with the Master-Detail Application Template
// Replace the file name with your momd's filename.

- (void)testCoreDataEquality {
    NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"TestCoreDataISEqual" withExtension:@"momd"];
    NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
    
    NSPersistentStoreCoordinator *storeCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    [storeCoordinator addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:nil];
    NSManagedObjectContext *mainQueueContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
    mainQueueContext.persistentStoreCoordinator = storeCoordinator;
    
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:mainQueueContext];
    
    NSManagedObject *mainQueueObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:mainQueueContext];
    
    NSManagedObjectContext *backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
    backgroundContext.persistentStoreCoordinator = storeCoordinator;
    
    __block NSManagedObject *backgroundObject;
    [backgroundContext performBlockAndWait:^{
        backgroundObject = [backgroundContext objectWithID:mainQueueObject.objectID];
    }];
        
    if ([mainQueueObject.objectID isEqual:backgroundObject.objectID]) {
        NSLog(@"The objectIDs are equal");
        
        if ([mainQueueObject isEqual:backgroundObject]) {
            NSLog(@"Core Data believes the objects are equal");
        }
        else {
            NSLog(@"Core Data believes the objects are not equal");
        }
    }
    else {
        NSLog(@"The objectIDs aren't equal");
    }
}

Prints out:

2013-06-09 00:18:41.048 TestCoreDataISEqual[88449:c07] The objectIDs are equal
2013-06-09 00:18:41.049 TestCoreDataISEqual[88449:c07] Core Data believes the objects are not equal