Unit test with example Core Data

Question

This is start of my XCTestCase class:

var moc: NSManagedObjectContext!

    override func setUp() {
        super.setUp()

        moc = self.setUpInMemoryManagedObjectContext()
        self.fillManagedObjectContextWithExampleData(moc)
    }

    func setUpInMemoryManagedObjectContext() -> NSManagedObjectContext {

        let modelName = "ProjectApp"
        let modelURL = NSBundle.mainBundle().URLForResource(modelName, withExtension:"momd")!
        let managedObjectModel = NSManagedObjectModel(contentsOfURL: modelURL)!

        let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)
        persistentStoreCoordinator.addPersistentStoreWithType(NSInMemoryStoreType, configuration: nil, URL: nil, options: nil, error: nil)

        let managedObjectContext = NSManagedObjectContext()
        managedObjectContext.persistentStoreCoordinator = persistentStoreCoordinator

        return managedObjectContext
    }

    func fillManagedObjectContextWithExampleData(context: NSManagedObjectContext) {
        // var firstSC = NSEntityDescription..insertNewObjectForEntityForName("StaticContent", inManagedObjectContext: context) as! StaticContent
        var staticContentEntity = NSEntityDescription.entityForName("StaticContent", inManagedObjectContext: context)!

        var firstSC = StaticContent(entity: staticContentEntity, insertIntoManagedObjectContext: context)
        firstSC.name = "First Name"

        var secondSC = StaticContent(entity: staticContentEntity, insertIntoManagedObjectContext: context)
        secondSC.name = "Second Name"

        var error: NSError? = nil

        if context.save(&error) {
            return
        }
    }

I just want to create managedObjectContext (in memory, just for testing) and fill it with example data. So I could use:

managedObjectContext.executeFetchRequest(fetchRequest, error: nil) as! [StaticContent]

in my unit tests. It executes but when I call function which takes [StaticContent] I got an error:

fatal error: NSArray element failed to match the Swift Array Element type

So what is a problem with this? My function which I call works fine. When I using it in my app and not in unit tests I don't have problem. So what I am doing wrong?

And btw, this may have something to do with the entity's managedObjectClassName being different in your test target: if your include your manage object subclass in your test target, its class name would be YourTestTarget.StaticContent... It can be solved with this workaround: https://gist.github.com/efa85/d82cc8fb0358e970e1e4 — e1985, Jul 01 '15 at 14:36
Thanks, I found similar code in another stackoverflow question. I was searching for solution for hour and then after I post my question I found it. — Libor Zapletal, Jul 01 '15 at 14:38

score 2 · Accepted Answer · answered Jul 01 '15 at 14:37

I really don't like to answer my question but I have found an answer and I want help the others. I found a part of code which changes entities class names according to which target they are run. So I have added these lines of code where I create NSManagedObjectModel and it helps:

    // Create the module name
    let moduleName = "ProjectAppTests"

    // Create a new managed object model with updated entity class names
    var newEntities = [] as [NSEntityDescription]
    for (_, entity) in enumerate(managedObjectModel.entities) {
        let newEntity = entity.copy() as! NSEntityDescription
        newEntity.managedObjectClassName = "\(moduleName).\(entity.name)"
        newEntities.append(newEntity)
    }
    let newManagedObjectModel = NSManagedObjectModel()
    newManagedObjectModel.entities = newEntities

    let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: newManagedObjectModel)

Don't know why it is so complicated with Class name in Core Data using Swift. But it helps and it's working now.

This looks quite similar to the solution proposed in http://stackoverflow.com/a/26796626/1187415. — Martin R, Jul 01 '15 at 15:08
After reading that question, I think the best solution is to use @objc(YourClass) as suggested in Christer's answer — e1985, Jul 01 '15 at 16:15
I was trying to use @objc(YourClass) but still I got problems with that. — Libor Zapletal, Jul 01 '15 at 19:42

taitelman · Answer 2 · 2017-09-03T08:45:23.327

in swift 3.0:

func setUpInMemoryManagedObjectContext() -> NSManagedObjectContext {
        let moduleName = "Model"
        do {
            let managedObjectContext = NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
            let modelURL = Bundle.main.url(forResource: moduleName, withExtension:"momd")
            let newObjectModel = NSManagedObjectModel.init(contentsOf: modelURL!)
            let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel : newObjectModel!)
            try  persistentStoreCoordinator.addPersistentStore(ofType: NSInMemoryStoreType, configurationName: nil, at: nil, options: nil)

            managedObjectContext.persistentStoreCoordinator = persistentStoreCoordinator
            return managedObjectContext
        } catch let error as NSError {
            logErr(error.localizedDescription)
            XCTFail()
        }
        XCTFail("failed to created mocked coreData (inMemroy)")
        return NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType)
    } 
func fillManagedObjectContextWithExampleData(context: NSManagedObjectContext) {
//lets assume you got some Food POJO class
    do {
        let foodJson: NSDictionary = ["id" : "1" , "foodId" : "1" , "displayName": "Pizza"]
        let firstFood = try Food.createOrUpdate(dict: foodJson, inManagedObjectContext: context)
        try  context.save()
        return
    } catch let error as NSError {
        logErr(error.localizedDescription)
    }
}

Unit test with example Core Data

2 Answers2