public void Quantity_kindly_handle_the_default_quantity_with_null_Unit()
        {
            var qDef = new Quantity();

            qDef.ToNormalizedString().Should().Be("0");
            qDef.CanConvertTo(MeasureUnit.None).Should().BeTrue();

            var kilo = 1.WithUnit(MeasureUnit.Kilogram);

            qDef.CanConvertTo(kilo.Unit).Should().BeFalse();
            qDef.CanAdd(kilo).Should().BeFalse();
            kilo.CanAdd(qDef).Should().BeFalse();

            var zeroKilo = qDef.Multiply(kilo);

            zeroKilo.ToNormalizedString().Should().Be("0 kg");

            (qDef * kilo).ToNormalizedString().Should().Be("0 kg");
            (kilo * qDef).ToNormalizedString().Should().Be("0 kg");
            (kilo.Multiply(qDef)).ToNormalizedString().Should().Be("0 kg");
            (qDef / kilo).ToNormalizedString().Should().Be("0 kg-1");

            var qDef2 = qDef.ConvertTo(MeasureUnit.None);

            qDef2.ToNormalizedString().Should().Be("0");
        }