it("should return kind", () => {
      var qty = Qty("1 mm");
      expect(qty.kind()).toBe("length");

      qty = Qty("1 N");
      expect(qty.kind()).toBe("force");
    });

Qty.parse('foo'); // => null

Qty.getKinds(); // => Array of names of every well-known kind of units

Qty.getUnits('currency'); // => [ 'dollar', 'cents' ]
// Or all alphabetically sorted
Qty.getUnits(); // => [ 'acre','Ah','ampere','AMU','angstrom']

Qty.getAliases('m'); // => [ 'm', 'meter', 'meters', 'metre', 'metres' ]

const qty1 = Qty('1m');
const qty2 = Qty('2m');

qty1.isCompatible(qty2); // => true or false

qty.kind(); // => 'length', 'area', etc...

qty.isUnitless(); // => true or false
qty.isBase(); // => true if quantity is represented with base units

qty.toBase(); // converts to SI units (10 cm => 0.1 m) (new instance)

qty.toFloat(); // returns scalar of unitless quantity (otherwise throws error)

qty.to('m'); // converts quantity to meter if compatible or throws an error (new instance)
qty1.to(qty2); // converts quantity to same unit of qty2 if compatible or throws an error (new instance)

qty.inverse(); // converts quantity to its inverse ('100 m/s' => '.01 s/m')
// Inverses can be used, but there is no special checking to
// rename the units
Qty('10ohm').inverse(); // '.1/ohm' (not '.1S', although they are equivalent)