Swift cannot test core data in Xcode tests?

Question

I am working on a iOS project that uses core data. I am using swift. The Core Data stack is setup right and all seems to be fine. I have created a class for an entity (NSManage

Answer 1

I also faced similar issue when I tried to write unit test cases for a sample app (MedicationSchedulerSwift3.0) written in Swift 3.0, apart from implementing solution provided by johnford I created a category on XCTestCase to setup an NSManagedObjectContext with in-memory store by using below code:

//  XCTestCase+CoreDataHelper.swift

import CoreData
import XCTest
@testable import Medication

extension XCTestCase {
    func setUpInMemoryManagedObjectContext() -> NSManagedObjectContext {
        let managedObjectModel = NSManagedObjectModel.mergedModel(from: [Bundle.main])!

        let persistentStoreCoordinator = NSPersistentStoreCoordinator(managedObjectModel: managedObjectModel)

        do {
            try persistentStoreCoordinator.addPersistentStore(ofType: NSInMemoryStoreType, configurationName: nil, at: nil, options: nil)
        } catch {
            print("Adding in-memory persistent store failed")
        }

        let managedObjectContext = NSManagedObjectContext(concurrencyType:.privateQueueConcurrencyType)
        managedObjectContext.persistentStoreCoordinator = persistentStoreCoordinator

        return managedObjectContext
    }
}

And used it like this:

//  NurseTests.swift

import XCTest
import CoreData
@testable import Medication

class NurseTests: XCTestCase {
    var managedObjectContext: NSManagedObjectContext?

    //MARK: Overriden methods
    override func setUp() {
        super.setUp()
        // Put setup code here. This method is called before the invocation of each test method in the class.
        if managedObjectContext == nil {
            managedObjectContext = setUpInMemoryManagedObjectContext()
        }
    }

//MARK:- Testing functions defined in Nurse.swift
    // testing : class func addNurse(withEmail email: String, password: String, inManagedObjectContext managedObjectContext: NSManagedObjectContext) -> NSError?
    func testAddNurse() {
        let nurseEmail = "clara@gmail.com"
        let nursePassword = "clara"

        let error = Nurse.addNurse(withEmail: nurseEmail, password: nursePassword, inManagedObjectContext: managedObjectContext!)
        XCTAssertNil(error, "There should not be any error while adding a nurse")
    }
}

In case if someone needs more examples they can look at unit test cases over here - MedicationTests