In memory CoreData configuration for unit testing

CoreDataHelper.swift

import Foundation
import CoreData

func setUpInMemoryManagedObjectContext() -> NSManagedObjectContext {
    let managedObjectModel = NSManagedObjectModel.mergedModelFromBundles([NSBundle.mainBundle()])!
    
    let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)
    do {
        try persistentStoreCoordinator.addPersistentStoreWithType(NSInMemoryStoreType, configuration: nil, URL: nil, options: nil)
    } catch {
        assertionFailure("Unable to setup coredata")
    }
    
    let managedObjectContext = NSManagedObjectContext()
    managedObjectContext.persistentStoreCoordinator = persistentStoreCoordinator
    
    return managedObjectContext
}

Usage:

let context = setUpInMemoryManagedObjectContext()
let myObject = NSEntityDescription.insertNewObjectForEntityForName("MyObject", inManagedObjectContext: context) as! MyObject