public function test_reduce()
{
$collection = new Collection(array(1, 2, 3, 4));
$result = $collection->reduce(function ($result, $v) {
return $result + $v;
});
$this->assertSame(10, $result, '1 + 2 + 3 + 4 = 10');
$this->assertSame(array(1, 2, 3, 4), $collection->toArray(), 'Original array should remain intact');
}