public void TestAdd()
{
Cartesian original = new Cartesian(10.0, 20.0, 30.0);
Cartesian toAdd = new Cartesian(1.0, 2.0, 3.0);
Cartesian result = original + toAdd;
Assert.AreEqual(11.0, result.X);
Assert.AreEqual(22.0, result.Y);
Assert.AreEqual(33.0, result.Z);
result = original.Add(toAdd);
Assert.AreEqual(11.0, result.X);
Assert.AreEqual(22.0, result.Y);
Assert.AreEqual(33.0, result.Z);
}