public void TestSumWithNegativeNumber()
 {
     Assert.AreEqual(-15, BasicMethods.Sum(-5));
 }
 public void TestSumWithZero()
 {
     Assert.AreEqual(0, BasicMethods.Sum(0));
 }
 public void TestSumWithOneNumber()
 {
     Assert.AreEqual(21, BasicMethods.Sum(6));
 }