import Foundation
import UIKit
​
@propertyWrapper
struct UnsafeBitCast<Actual: NSObjectProtocol, Mocked: NSObjectProtocol> {
    init(wrappedValue: Actual?, to mocked: Mocked.Type) {
        self.wrappedValue = wrappedValue
    }
    var wrappedValue: Actual?
    var projectedValue: Mocked? {
        wrappedValue.map({ unsafeBitCast($0, to: Mocked.self) }) // fix-it suggests unsafeDowncast
    }
}
​
class MockUIWindow: NSObject {
    @UnsafeBitCast(to: UIScene.self) var mockWindowScene: MockUIScene? = nil
    init(mockWindowScene: MockUIScene? = .init()) {
        self.mockWindowScene = mockWindowScene
    }
    var windowScene: UIScene? {
        $mockWindowScene
    }
}
​
class MockUIScene: NSObject {
    @objc var activationState: UIScene.ActivationState
    init(activationState: UIScene.ActivationState = .foregroundActive) {
        self.activationState = activationState
    }
}
​
let mockWindow = MockUIWindow()
print(mockWindow.windowScene!.activationState == .foregroundActive)