public void T10_should_decompose()
        {
            var d = new DensityUnit(MassUnits.Gram, VolumeUnits.CubicFeet);
            var g = d.Decompose();

            Assert.Equal(2, g.Count);
            Assert.Equal(MassUnits.Gram, (MassUnit)g[0].Unit);
            Assert.Equal(1, g[0].Power);
            Assert.Equal(LengthUnits.Feet, (LengthUnit)g[1].Unit);
            Assert.Equal(-3, g[1].Power);
        }