public void Test_Iterations(int startIteration, int numberOfIterations, double expected)
        {
            var pi = new Gregory_Leibniz();

            pi.Iterations(startIteration, numberOfIterations);
            Assert.That(Math.Abs(expected - pi.Calculate()), Is.LessThan(0.000001));
        }
        public void Test_NumberOfIterations(int iterations, double expectedDifference)
        {
            var pi = new Gregory_Leibniz();

            pi.NumberOfIterations = iterations;
            Assert.That(Math.Abs(3.14159265359 - pi.Calculate()), Is.LessThan(expectedDifference));
        }