Phpunit test simple getPath() method

Question

*This is a beginner's question in phpunit so i don't know if it belongs here or not.

I want to test that the var path is correct, but I'm getting Failed asserting that null matches expected '/magento2/var'.

I suppose because I am using a mock for DirectoryList, instead instantiating the class. How does one test it? Should I instantiate DirectoryList? I am having issues with it's constructor...

<?php
namespace Vendor\Module\Cron;
use Magento\Framework\App\Filesystem\DirectoryList;
class Products {
 /**
 * Retrieve var path
 *
 * @return string
 */
 protected $directory_list;
 public function __construct(
 DirectoryList $directory_list
 )
 {
 $this->directory_list = $directory_list;
 }
 /**
 * Retrieve var path
 *
 * @return string
 */ 
 public function getVarFolderPath()
 {
 return $this->directory_list->getPath('var');
 }
}

and my test:

<?php
namespace Vendor\Module\Test\Unit\Model;
use Magento\Framework\App\Filesystem\DirectoryList;
use Vendor\Module\Cron\Products;
class ProductsTest extends \PHPUnit_Framework_TestCase
{
 /**
 * @var string
 *
 * dummy var path
 */
 const VAR_PATH = '/magento2/var';
 /**
 * @var Vendor\Module\Cron\Products;
 */
 protected $products;
 /**
 * setup tests
 */
 protected function setUp()
 {
 /** @var \PHPUnit_Framework_MockObject_MockObject|DirectoryList */
 $directoryListMock = $this->getMockBuilder(DirectoryList::class)
 ->disableOriginalConstructor()
 ->getMock();
 $this->products = new Products(
 $directoryListMock
 );
 }
 /**
 * @test Vendor\Module\Cron\Products::getVarFolderPath()
 */
 public function testGetVarFolderPath()
 {
 $this->assertEquals(self::VAR_PATH, $this->products->getVarFolderPath());
 }
}

Update: so Kandy's answer was ok. in unit test you test just that specific class.

Answer 1

All mocked methods returns null, so you need describe in your test what getPath method will return:

$directoryListMock->expects($this->any())
->method('getPath')
->with('var')
->willReturn(self::VAR_PATH);

• Claudiu Creanga: and that will actually test anything? to me it looks like I am asserting that self::VAR_PATH == self::VAR_PATH and not actually testing the result of getVarFolderPath
• KAndy: This is because your code does not do anything ;)
• Claudiu Creanga: Sorry but I don't understand what you mean by the code doesn't do anything. I just want to test that $this->directory_list->getPath always returns a specific string because my host often changes paths and I have a third party extension that inserts files in the var folder. So I am unsure how to do it. Should I load the object DirectoryList and not make a mock?