AVPlayerItem Status Observer - Unit Test Status Changes - swift

Question

Does anyone have any references on unit testing key value observing logic in swift? I'd like to mock the AVPlayerItem's status changes in my unit tests to confirm that the expected logic is triggered. For simplicity this is what I have so far:
A function that observes the provided playerItem's status
public func observePlayerItemStatus(playerItemToObserve: AVPlayerItem) -> NSKeyValueObservation {
let observerToken = playerItemToObserve.observe(\.status, options: [.new, .old], changeHandler: { (playerItemToObserve, _) in
switch playerItemToObserve.status {
case .failed:
// failed logic
case .readyToPlay:
// ready to play logic
default:
// default logic
}
})
return observerToken
}
I've created a mock class, MockAVPlayerItem
class MockAVPlayerItem: AVPlayerItem {
var mockStatus: AVPlayerItem.Status = .unknown
public override var status: AVPlayerItem.Status {
get { return mockStatus }
set { self.mockStatus = newValue }
}
}
My unit test attempting to trigger the status code change does the following:
func test_readyToPlayIsTriggered() {
let url = URL(string: "https://www.rmp-streaming.com/media/big-buck-bunny-360p.mp4")!
let mockPlayerItem = MockPlayerItem(url: url)
let statusToken = observePlayerItemStatus(playerItemToObserve: mockPlayerItem)
mockPlayerItem.status = .readyToPlay
... some assertion that ready to play was called ....
}
The logic itself works when I run the application however my unit tests are unable to trigger my observer. I've followed a similar approach to mock AVPlayer.timeControlStatus and it's worked great but for some reason AVPlayerItem.status isn't behaving the same.

Answer 1

Using a willChangeValue and didChangeValue in my mock solved my problem. Observers are now triggered as expected.
class MockAVPlayerItem: AVPlayerItem {
var mockStatus: AVPlayerItem.Status = .unknown
public override var status: AVPlayerItem.Status {
get { return mockStatus }
set {
willChangeValue(for: \.status)
self.mockStatus = newValue
didChangeValue(for: \.status)
}
}
}