public void CheckAgeTheory(int age)
        {
            var sut = new PlayerExpert();

            sut.age = age;


            Assert.Equal(sut.age, age);
        }
        public void CheckTypeSoft()
        {
            var sut = new PlayerExpert();

            sut.age = 34;


            Assert.IsAssignableFrom <Player>(sut);
        }
        public void CheckException()
        {
            var sut = new PlayerExpert();

            sut.age = 34;


            Assert.Throws <ArgumentNullException>(() => sut.CauseArgNulEx(null));
        }
        public void CheckType()
        {
            var sut = new PlayerExpert();  // well.. should be generated by some factory

            sut.age = 34;


            Assert.IsType <PlayerExpert>(sut);  // strict test
        }