public void MassFractionFromMassesConstructedCorrectly()
{
var one_kg = Mass.FromKilograms(1);
var two_kg = Mass.FromKilograms(2);
var massFraction = MassFraction.FromMasses(one_kg, two_kg);
AssertEx.EqualTolerance(50, massFraction.Percent, PercentTolerance);
}