unwrite if statements with switch and case, php gilded rose

one text

https://github.com/emilybache/GildedRose-Refactoring-Kata/tree/main/php

im doing the gilded rose refactoring kata for php right now. I have written some unittests and they all work with the standard GildedRose.php code. Now i wanted to refactory the 40 line of if statements to do the code easier to read, but somewhere a mistake has crept in and idk where and how.

my unittest are like (for each item):

public function testAgedBrieAtBeginning(): void          //  +1 quality till sell_in = 0 than +2 quality
{
    $items = [new Item('Aged Brie', 2, 0)];
    $gildedRose = new GildedRose($items);
    $gildedRose->updateQuality();
    $this->assertEquals($items[0]->sell_in, 1);
    $this->assertEquals($items[0]->quality, 1);
}

public function testAgedBrieWhenSellInZero(): void
{
    $items = [new Item('Aged Brie', 0, 2)];
    $gildedRose = new GildedRose($items);
    $gildedRose->updateQuality();
    $this->assertEquals($items[0]->sell_in, -1);
    $this->assertEquals($items[0]->quality, 4);
}

public function testAgedBrieDontIncreaseMaximum(): void       // stand at 50 quality
{
    $items = [new Item('Aged Brie', -28, 50)];
    $gildedRose = new GildedRose($items);
    $gildedRose->updateQuality();
    $this->assertEquals($items[0]->sell_in, -29);
    $this->assertEquals($items[0]->quality, 50);
}

and my GildedRose.php is:

<?php

declare(strict_types=1);

namespace GildedRose;

final class GildedRose
{
/**
 * @var Item[]
 */
private $items;

public function __construct(array $items)
{
    $this->items = $items;

}

public function updateQuality(): void
{
    switch ($this->items) {
        case 'Normal':
            $this->tickNormal();
            return;
        case 'Aged Brie':
            $this->tickAgedBrie();
            return;
        case 'Sulfaras, Hand of Ragnaros':
            $this->tickSulfuras();
            return;
        case 'Backstage passes to a TAFKAL80ETC concert':
            $this->tickBackstage();
            return;
    }

}

private function tickNormal(): void  // for Dexterity, Elixir & Conjured
{
    $this->sell_in--;

    if($this->quality == 0) {
        return;
    }

    $this->quality--;
    if ($this->sell_in <= 0) {
        $this->quality--;
    }
}
private function tickAgedBrie()
{
    $this->sell_in -= 1;

    if($this->quality >= 50) {
        return;
    }

    $this->quality += 1;
    if ($this->sell_in <= 0) {
        $this->quality += 1;
    }
}

private function tickSulfuras() : void
{

}

private function tickBackstage() : void
{
    $this->sell_in -= 1;

    if ($this->quality >= 50) {
        return;
    }
    if ($this->sell_in < 0) {
        $this->quality = 0;
        return;
    }

    $this->quality += 1;
    if ($this->sell_in < 10) {
        $this->quality += 1;
    }
    if ($this->sell_in < 5) {
        $this->quality += 1;
    }
}

}

Firstly: The code was a full chaos. Look at the github repository /src/GildedRose.php. I have write some unittest to the original code to save the program. my unittest looks all similar to above. I test the changes of every items as they should be (https://github.com/emilybache/GildedRose-Refactor). After the unittests, i started to change the GildedRose.php to uncode the if-statements..