public void TestFlip(double a1_0, double a1_1, double e_0, double e_1)
        {
            AxisPosition pos1     = new AxisPosition(a1_0, a1_1);
            AxisPosition expected = new AxisPosition(e_0, e_1);
            AxisPosition result   = pos1.Flip();

            Assert.AreEqual(expected, result);
        }