it("should multiply temperature degrees", () => {
      var qty = Qty("2degF");
      var result = qty.mul(3);
      expect(result.scalar).toBe(6);
      expect(result.units()).toBe("degF");

      result = qty.mul("3degF");
      expect(result.scalar).toBe(6);
      expect(result.units()).toBe("degF2");

      // TODO: Should we convert degrees ("2 degK" to "degC") before we do the math?
      qty = Qty("2degC");
      result = qty.mul("2degK");
      expect(result.scalar).toBe(4);
      expect(result.units()).toBe("degC*degK");

      qty = Qty("2degC");
      result = qty.mul("degF");
      expect(result.scalar).toBe(2);
      expect(result.units()).toBe("degC*degF");
    });

 expect(() => { qty.mul("-1"); }).toThrow("Temperatures must not be less than absolute zero");

 expect(function () { qty.mul("1 degC"); }).toThrow("Cannot multiply by temperatures");