a := test.a.DeepCopy()
		a.Neg()
		// ensure value is same
		if a.Cmp(test.expected) != 0 {
			t.Errorf("[%d] Expected %q, got %q", i, test.expected.String(), a.String())
		}
	}
}

func TestAdd(t *testing.T) {
	tests := []struct {
		a        Quantity
		b        Quantity
		expected Quantity
	}{
		{decQuantity(10, 0, DecimalSI), decQuantity(1, 1, DecimalSI), decQuantity(20, 0, DecimalSI)},