Unit testing DI with CoreData won't work - ios

Question

I'm trying to write a test to make sure that my view model's model property when set calls my fetchPlan method from the model and then sets my 'plan' property in my view model. It seems to be setting the property but the values are missing...
Here's my view model
final class PlanProgressViewModel: PlanProgressViewModelView {
// MARK: - Properties
fileprivate var plan: PlanData?
// MARK: - PlanProgressViewModelView
weak var viewDelegate: PlanProgressViewModelViewDelegate?
var model: PlanModel? {
didSet {
model?.fetchCurrentPlan(completionHandler: { (plan) in
guard let plan = plan else {return}
self.plan = plan
})
}
}
// Testing this fails...
var planName: String! {
guard let plan = plan else {return "No plan"}
return plan.name
}
var planProgressionString: String! {
return "\(Int(round(self.progress * 100)))%"
}
var progress: Double! {
guard let plan = plan, let workouts = plan.workouts, let completedWorkouts = plan.completedWorkouts else {return 0}
return Double(Int(completedWorkouts) / workouts.count)
}
}
Here's my test suite, i'm using a mock to return hardcoded data from the model.
var sut: PlanProgressViewModel!
var model: MockPlanModel!
var moc: NSManagedObjectContext!
override func setUp() {
super.setUp()
moc = setupInMemoryMOC()
let mockModel = MockPlanModel(moc: moc)
model = mockModel
let viewModel = PlanProgressViewModel()
viewModel.model = model
sut = viewModel
}
override func tearDown() {
moc = nil
model = nil
sut = nil
super.tearDown()
}
// This passes
func testModelFetchesCurrentPlanOnce() {
XCTAssertEqual(model.fetchPlanWasCalled, 1)
}
// This is failing
func testPlanName() {
XCTAssertEqual(sut.planName, "Test plan")
}
Here's my method for setting up a in memory persistent store...
public func setupInMemoryMOC() -> NSManagedObjectContext {
let mom = NSManagedObjectModel.mergedModel(from: [Bundle.main])
let psc = NSPersistentStoreCoordinator(managedObjectModel: mom!)
do {
try psc.addPersistentStore(ofType: NSInMemoryStoreType, configurationName: nil, at: nil, options: nil)
} catch {
fatalError()
}
let moc = NSManagedObjectContext.init(concurrencyType: .mainQueueConcurrencyType)
moc.persistentStoreCoordinator = psc
return moc }
Here's my mock for the model which returns hardcoded data...
public class MockPlanModel: MWPlanModel {
var fetchPlanWasCalled = 0
override public func fetchCurrentPlan(completionHandler: #escaping (_ plan: PlanData?) -> ()) {
fetchPlanWasCalled += 1
let moc = setupInMemoryMOC()
let plan = createTestPlan(moc: moc)
completionHandler(plan)
}}
Here's my helper method for creating the model object, (PlanData is a protocol that my 'Plan' NSManaged object inherits).
public func createTestPlan(moc: NSManagedObjectContext) -> PlanData {
let plan: Plan = Plan(context: moc)
plan.name = "Test plan"
plan.completedWorkouts = 5
plan.currentPlan = true
for _ in 0..<5 {
plan.mutableOrderedSetValue(forKeyPath: #keyPath(Plan.workouts)).add(createTestCompletedWorkout(moc: moc))
}
return plan }
The plan name should be "Test plan" as that is what i set the hardcoded value to be but it fails and returns an empty string instead...
Really stuck on this, i'm fairly new to testing so i appreciate any help with this. Thanks

Answer 1

#MartinR comment good point out :
The non-optional on the left side "Test plan" gets automatically promoted to an optional. because sut.planName is an optional. more check this Swift comparing Strings optionals vs non-optional
You need to unwrap sut.planName
if let planName = sut.planName{
XCTAssertEqual(planName, "Test plan")
}
Or try this way :
XCTAssertEqual((sut.planName ?? ""), "Test plan")
Note: If you face still same issue then update your Xcode
// Using Apple XCTest (Xcode 7.3.1), this produces the output:
// "XCTAssertEqual failed: ("Optional(1)") is not equal to ("Optional(2)") - "
XCTAssertEqual(1, 2)
More details : Here Bug reported