Ios 如何通过S定义的对象设置删除基于块的观察者的测试

假设我有这样的代码:

class Foo {

    private let nc: NotificationCenter
    
    init(nc: NotificationCenter = .default) {
        self.nc = nc
        
        nc.addObserver(forName: Notification.Name.Foo, object: nil, queue: .main) { _ in
            Task { [weak self] in
                self?.doSomething()
            }
        }
    }

    deinit {
        nc.removeObserver(self, name: Notification.Name.Foo, object: nil)
    }

    @objc
    private func doSomething() async {
        // triggers some async code
    }
}

我想要编写一个单元测试，以确保在释放类时删除该观察器.

苹果公司的文件规定:

如果您使用addWatch(forName:Object:Queue:Using:)来创建您的观察器，则应在系统释放addWatch(forName:Object:Queue:Using:)指定的任何对象之前调用此方法或移除该方法或删除该方法(_:name:Object:).

我曾嘲笑过一个通知中心:

class MockNotificationCenter: NotificationCenter {

    var notifications: [NSNotification.Name?] = []

    override func addObserver(
        forName name: NSNotification.Name?,
        object obj: Any?,
        queue: OperationQueue?,
        using block: @escaping (Notification) -> Void) -> NSObjectProtocol
    {
        notifications.append(name)
        return super.addObserver(forName: name, object: obj, queue: queue, using: block)
    }

    override func removeObserver(
        _ observer: Any, 
        name aName: NSNotification.Name?, 
        object anObject: Any?
    ) {
        notifications = notifications.filter { $0 != aName }
        super.removeObserver(observer, name: aName, object: anObject)
    }

下面是我的单元测试:

    func testDeinit_DoesRemoveObserver() {
        // Given
        var sut: Foo?
        let mockNC = MockNotificationCenter()
        // When
        sut = Foo(notificationCenter: mockNC)
        // Then
        XCTAssertEqual(mockNC.notifications.count, 1) // Succeeds
        // When
        sut = nil
        // Then
        XCTAssertEqual(mockNC.notifications.count, 0) // Fails
    }

XCTAssertEqual失败:("1")不等于("0")

我如何解决这个问题，以断言观察者在我的观察对象解除分配后已从通知中心移除？