public function testNth()
{
$this->assertEquals(1, P::nth(0, [1, 2, 3]));
$this->assertEquals(2, P::nth(1, [1, 2, 3]));
$this->assertEquals(NULL, P::nth(2, []));
$this->assertEquals(3, P::nth(2, ["a" => 1, "b" => 2, "c" => 3]));
}