[differences between loading persistent container within the app or unit test

CoreDataPersistentContainerUniteTest.swift

// Inside the app (SQLite)
lazy var persistentContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "CoreDataUnitTesting")
  
    container.loadPersistentStores { (description, error) in
        if let error = error {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
    }
    return container
}()

// Inside the test (in-memory)
lazy var mockPersistantContainer: NSPersistentContainer = {
    let container = NSPersistentContainer(name: "CoreDataUnitTesting", managedObjectModel: self.managedObjectModel)
  
    let description = NSPersistentStoreDescription()
    description.type = NSInMemoryStoreType
    description.shouldAddStoreAsynchronously = false
  
    container.persistentStoreDescriptions = [description]
  
    container.loadPersistentStores { (description, error) in
        precondition(description.type == NSInMemoryStoreType)
        
        if let error = error {
            fatalError("In memory coordinator creation failed \(error)")
        }
    }
    return container
}()

var managedObjectModel: NSManagedObjectModel = {
  let managedObjectModel = NSManagedObjectModel.mergedModel(from: [Bundle.main])!
  return managedObjectModel
}()