public void Abs(double value, AngularUnit unit, double expected)
        {
            var v  = new Measurement <AngularUnit>(value, unit);
            var v1 = MeasurementMath.Abs(v);

            v1.Value.Should().BeApproximately(expected, 1e-10);
            v1.Unit.Should().Be(unit);

            var v2 = v.Abs();

            v2.Value.Should().BeApproximately(expected, 1e-10);
            v2.Unit.Should().Be(unit);
        }