y := new(Int)

	if a.Sign() <= 0 || b.Sign() <= 0 {
		return true // can only test positive arguments
	}

	d := new(Int).lehmerGCD(x, y, a, b)
	d0, x0, y0 := euclidExtGCD(a, b)

	return d.Cmp(d0) == 0 && x.Cmp(x0) == 0 && y.Cmp(y0) == 0
}

var gcdTests = []struct {
	d, x, y, a, b string
}{
	// a <= 0 || b <= 0
	{"0", "0", "0", "0", "0"},
	{"7", "0", "1", "0", "7"},