How to test NSPersistentDocument in XCTestCase?

I'm just starting an OS X document-based app using Core Data. To test my model relationships, I'd like to create some NSManagedObject entities, save them to a file, and read them back in an XCTestCase object. Using code like below, I can create entities in the managed object context, but I cannot figure out how to create a functioning persistent store coordinator and/or save to a file.

class MyTests: XCTestCase {

    var doc: Document!
    var moc: NSManagedObjectContext!
    //...//

    override func setUp() {
        super.setUp()
        doc = Document()
        moc = doc.managedObjectContext
    }

    //...//
}

Problem with my initial approach above was that I was getting the managedObjectContext before using configurePersistentStoreCoordinatorForURL. Once I resolved that, the solution was fairly straightforward.

class DocTests : XCTestCase {

    let testFileURL = NSURL.fileURLWithPath("/Users/Me/Temp/DocTests", isDirectory: false)

    override func setUp() {
        super.setUp()
    }

    func testWriteAndRead() {

        writeSimpleTestDocument()

        let doc = Document()        
        do {
            try doc.readFromURL(testFileURL, ofType: "mydoctype")
        } catch let error as NSError {
            print("Failed to read, \(error), \(error.userInfo)")
        }

        let moc = doc.managedObjectContext!

        // fetch from moc and verify test entities here ...
        // ...
    }


    func writeSimpleTestDocument() {

        // if test document exists, delete it
        let fm = NSFileManager.defaultManager()

        if fm.fileExistsAtPath(testFileURL.path!) {
            do {
                try fm.removeItemAtURL(testFileURL)
            } catch let error as NSError {
                print("Failed to remove, \(error), \(error.userInfo)")
            }
        }

        let doc = Document()

        do {
            try doc.configurePersistentStoreCoordinatorForURL(testFileURL, ofType: "mydoctype", modelConfiguration: nil, storeOptions: nil)
        } catch let error as NSError {
            print("Failed to configure coordinator, \(error), \(error.userInfo)")
        }

        let moc = doc.managedObjectContext!

        // create test entities in moc here ...
        // ...

        do {
            try moc.save()
        } catch let error as NSError {
            print("Failed to save, \(error), \(error.userInfo)")
        }
    }

}