A method that you can use in your test cases so you'll have a managed object context around.

gistfile1.m

- (NSManagedObjectContext*)managedObjectContextForTesting {
  NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"YourModelName" withExtension:@"momd"];
  NSManagedObjectModel* model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
  NSPersistentStoreCoordinator* coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];
  [coordinator addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:NULL];
  NSManagedObjectContext* managedObjectContext= [[NSManagedObjectContext alloc] init];
  managedObjectContext.persistentStoreCoordinator = coordinator;
  return managedObjectContext;
}