public void GetFactorial() { int i; int r, a; i = 0; r = MathTool.GetFactorial(i); a = 1; Assert.IsTrue(r == a); i = 4; r = MathTool.GetFactorial(i); a = 24; Assert.IsTrue(r == a); i = -2; Assert.ThrowsException <ArgumentException>(() => MathTool.GetFactorial(i)); }