Adding CoreData to XCTest

XCTestCase+CoreData.m

@implementation XCTestCase(CoreData)

+ (id)fakeEntityForTests:(Class)clazz {
    NSEntityDescription *entityDesc = [NSEntityDescription entityForName:NSStringFromClass(clazz)
                                                  inManagedObjectContext:[[self class] managedObjectContextForTests]];
    return [[clazz alloc] initWithEntity:entityDesc
          insertIntoManagedObjectContext:[[self class] managedObjectContextForTests]];
}

+ (NSManagedObjectContext *)managedObjectContextForTests {
    static NSManagedObjectModel *model = nil;
    if (!model) {
        model = [NSManagedObjectModel mergedModelFromBundles:[NSBundle allBundles]];
    }
    
    NSPersistentStoreCoordinator *psc = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
    NSPersistentStore *store = [psc addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:nil];
    NSAssert(store, @"Should have a store by now");

    // To keep a unique Context !    
    static NSManagedObjectContext *moc = nil;
    if (!moc) {
        moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
        moc.persistentStoreCoordinator = psc;
    }
    
    return moc;
}

@end