gistfile1.swift

import UIKit
import CoreData

class SomeClass: NSManagedObject {}

class MyManagedObjectContext: NSManagedObjectContext {
    
    override func executeFetchRequest(request: NSFetchRequest) throws -> [AnyObject] {
        return [SomeClass()]
    }
    
}

let context = MyManagedObjectContext(concurrencyType: .PrivateQueueConcurrencyType)

let result = try context.executeFetchRequest(NSFetchRequest()) as? [SomeClass]

print(result!.first!)