}
	}
}

func testFunNN(t *testing.T, msg string, f funNN, a argNN) {
	z := f(nil, a.x, a.y)
	if z.cmp(a.z) != 0 {
		t.Errorf("%s%+v\n\tgot z = %v; want %v", msg, a, z, a.z)
	}
}

func TestFunNN(t *testing.T) {
	for _, a := range sumNN {
		arg := a
		testFunNN(t, "add", nat.add, arg)

		arg = argNN{a.z, a.y, a.x}
		testFunNN(t, "add symmetric", nat.add, arg)