TestViewControllerTransitionCoordinator.swift

func makeTestViewControllerTransitionCoordinator() -> UIViewControllerTransitionCoordinator {
    
    class ViewControllerTransitionCoordinator: NSObject, UIViewControllerTransitionCoordinatorContext, UIViewControllerTransitionCoordinator {

        public var isAnimated: Bool { return false }
        
        public var presentationStyle: UIModalPresentationStyle { return .formSheet }
        
        public var initiallyInteractive: Bool { return false }
        
        @available(iOS 10.0, *)
        public var isInterruptible: Bool { return false }
        
        public var isInteractive: Bool { return false }
        
        public var isCancelled: Bool { return false }
        
        public var transitionDuration: TimeInterval { return 1 }

        public var percentComplete: CGFloat { return 0 }
        
        public var completionVelocity: CGFloat { return 1 }
        
        public var completionCurve: UIViewAnimationCurve { return .easeIn }

        @available(iOS 2.0, *)
        public func viewController(forKey key: UITransitionContextViewControllerKey) -> UIViewController? {
            return nil
        }

        @available(iOS 8.0, *)
        public func view(forKey key: UITransitionContextViewKey) -> UIView? {
            return nil
        }
        
        @available(iOS 2.0, *)
        public var containerView: UIView { return UIView() }

        @available(iOS 8.0, *)
        public var targetTransform: CGAffineTransform { return .identity }
        
        @available(iOS 10.0, *)
        public func notifyWhenInteractionChanges(_ handler: @escaping (UIViewControllerTransitionCoordinatorContext) -> Void) {
            
        }
        
        @available(iOS, introduced: 7.0, deprecated: 10.0, message: "Use notifyWhenInteractionChangesUsingBlock")
        public func notifyWhenInteractionEnds(_ handler: @escaping (UIViewControllerTransitionCoordinatorContext) -> Void) {
            
        }

        func animate(alongsideTransition animation: ((UIViewControllerTransitionCoordinatorContext) -> Void)?, completion: ((UIViewControllerTransitionCoordinatorContext) -> Void)?) -> Bool {
            return true
        }
        
        func animateAlongsideTransition(
            in view: UIView?,
            animation: ((UIViewControllerTransitionCoordinatorContext) -> Void)?,
            completion: ((UIViewControllerTransitionCoordinatorContext) -> Void)?
            ) -> Bool {
            return true
        }
        
    }
    
    return ViewControllerTransitionCoordinator()
    
}

// Setup your test...

        viewController.viewWillTransition(to: .zero, with: makeTestViewControllerTransitionCoordinator())

// Validate the output...