public void Test1()
 {
     // Don't forget the special cases!
     Assert.Equal(Kata.Factorial(1), 1);
     Assert.Equal(Kata.Factorial(5), 120);
     Assert.Equal(Kata.Factorial(0), 1);
 }
 public void TestNegativeNumbers()
 {
     Assert.Throws <Exception>(() => Kata.Factorial(-1));
 }