Unit testing for UNUserNotificationCenter .requestAuthorization in Swift 5

Question

I am using test-driven development on Xcode and in Swift to develop an app.

I want to add timed notification alerts to remind people to come back to the app to perform an action. To do that I need to request authorization from my user using the notification center.

To do this, I want to write a test in my unit tests that only passes when the shared UNUserNotificationCenter instance calls its requestAuthorization(options:completionHandler:) method.

I have tried mocking UNUserNotificationCenter:

extension NotificationsExperimentsTests {

    class MockNotificationCentre: UNUserNotificationCenter {

        var didRequestAuthorization = false

        override func requestAuthorization(options: UNAuthorizationOptions = [], completionHandler: @escaping (Bool, Error?) -> Void) {
            didRequestAuthorization = true
        }
    }
}

But then when I try and initialise it in a test,

func test_requestAuthorization_IsCalled() {

    var mockNotificationCenter = MockNotificationCentre()
}

the compiler tells me that:

'NotificationsExperimentsTests.MockNotificationCentre' cannot be constructed because it has no accessible initializers

I'm not sure what to try next, or even whether what I'm trying to do is possible?

Does this help you? https://stackoverflow.com/questions/40862551/unit-testing-ios-10-notifications — Ramy Al Zuhouri, Nov 20 '19 at 18:00
Thank you, unfortunately not, I've been looking at it. With some syntax revisions it works fine in a Playground, but when I transfer it to separate test and build targets it won't compile. — Kramer, Nov 20 '19 at 18:09
If I define the MockNotificationCenter within an extension to my testClass then I get: "Cannot assign value of type 'testClass.MockNotificationCenter' to type 'UNUserNotificationCenter'" If I move the definition outside of the test class, I get essentially the same message: "Cannot assign value of type 'MockNotificationCenter' to type 'UNUserNotificationCenter'" — Kramer, Nov 20 '19 at 18:30

Kramer · Accepted Answer · 2019-11-24T11:41:03.767

So here's where I'm at so far. With thanks to this previous answer:

Unit testing iOS 10 notifications

My testclass:

import XCTest
import UserNotifications

@testable import NotificationsExperiments

class TestClass: XCTestCase {

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

  func testDoSomething() {
        //Given
        // Class being tested
        let exampleClass = ExampleClass()
        // Create your mock class.
        let mockNotificationCenter = MockNotificationCenter()
        exampleClass.notificationCenter = mockNotificationCenter
    //When
        exampleClass.doSomething()
        //Then
        XCTAssertTrue(mockNotificationCenter.didRequestAuthorization)
  }
}


extension TestClass {

    class MockNotificationCenter: MockUserNotificationCenterProtocol {

        var didRequestAuthorization = false

        func requestAuthorization(options: UNAuthorizationOptions, completionHandler: ((Bool, Error?) -> Void)) {
            didRequestAuthorization = true
        }
    }
}

My Example class:

import Foundation
import UserNotifications

class ExampleClass {

    #if DEBUG
    var notificationCenter: MockUserNotificationCenterProtocol = UNUserNotificationCenter.current()
    #else
    var notificationCenter = UNUserNotificationCenter.current()
    #endif

    func doSomething() {
        let options: UNAuthorizationOptions = [.alert, .sound, .badge]
        notificationCenter.requestAuthorization(options) {
            (didAllow, error) in
            if !didAllow {
                print("User has declined notifications")
            }
        }
  }
}

#if DEBUG
protocol MockUserNotificationCenterProtocol: class {
    func requestAuthorization(options: UNAuthorizationOptions, completionHandler: ((Bool, Error?) -> Void))

}

extension UNUserNotificationCenter: MockUserNotificationCenterProtocol {
    func requestAuthorization(options: UNAuthorizationOptions, completionHandler: ((Bool, Error?) -> Void)) {
        print("Requested Authorization")
    }
}
#endif

This does work, but it's more than a bit hacky. In DEBUG mode it doesn't actually send a request for authorization, but it does when it's released.

Any further contributions would be gladly accepted.

Unit testing for UNUserNotificationCenter .requestAuthorization in Swift 5

1 Answers1