PayPal\Api\ItemList::addItem PHP Method

    public function addItem($item)
    {
        if (!$this->getItems()) {
            return $this->setItems(array($item));
        } else {
            return $this->setItems(array_merge($this->getItems(), array($item)));
        }
    }

 public function testRemoveItemMethod()
 {
     $itemList = new ItemList();
     $item1 = ItemTest::createItem();
     $item1->setName("Name1");
     $item2 = ItemTest::createItem();
     $itemList->addItem($item1);
     $itemList->addItem($item2);
     $itemList->removeItem($item2);
     $this->assertEquals(sizeof($itemList->getItems()), 1);
     $remainingElements = $itemList->getItems();
     $this->assertEquals($remainingElements[0]->getName(), "Name1");
 }