it("should return null when passing an invalid quantity", () => {
   expect(Qty.parse("aa")).toBeNull();
 });

qty = Qty('1 m^2/s^2');
qty = Qty('1 m^2 s^-2'); // negative powers
qty = Qty('1 m2 s-2'); // ^ is optional

qty = Qty('1 m^2 kg^2 J^2/s^2 A');

qty = Qty('1.5'); // unitless quantity
qty = Qty(1.5); // number as initializing value

qty = Qty('1 attoparsec/microfortnight');

let qtyCopy: Qty;

qtyCopy = Qty(qty); // quantity could be copied when used as initializing value

Qty.parse('1 m'); // => 1 meter
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

 expect(() => { Qty.parse("foo"); }).not.toThrow("Argument should be a string");

 expect(function () { Qty.parse("foo"); }).not.toThrow("Argument should be a string");