public void StartEngineTest()
        {
            //
            ToyPlane toy = new ToyPlane();

            toy.StartEngine();
            Assert.AreEqual(toy.Engine.isStarted, false);
            //
            toy.windUp();
            toy.StartEngine();
            Assert.AreEqual(toy.Engine.isStarted, true);
        }
        public void WindUpTest()
        {
            ToyPlane toy = new ToyPlane();
            //isWoundUp = false
            string isWoundUpString = toy.getWindUpString();

            Assert.AreEqual(isWoundUpString, $"{toy} is not wound up.");
            //isWoundUp = true;
            toy.windUp();
            isWoundUpString = toy.getWindUpString();
            Assert.AreEqual(isWoundUpString, $"{toy} is wound up.");
        }
        public void TakeOffTest()
        {
            //
            ToyPlane toy           = new ToyPlane();
            string   TakeOffString = toy.TakeOff();

            Assert.AreEqual(TakeOffString, "You need to start the engine!");
            //
            toy.windUp();
            toy.StartEngine();
            toy.TakeOff();
            TakeOffString = toy.TakeOff();
            Assert.AreEqual(TakeOffString, "You are flying");
            //
        }