As a Magento Open Source Developer, you should have to write Unit Tests for the modules to validate the code is errorless and bug-free.

What is Unit Testing in Magento Open Source?

Unit Testing is a crucial operation, a set of the smallest testable parts of an application, which are called units, in the development of software. The unit testing will ensure that the codes you wrote are running correctly as well as raise the software quality you created before. In addition, remember that the unit testing process is separate and completely automatic without any manual handling.

Why Unit Test?

The main objective of Magento Open Source unit testing is to isolate written code to test and determine if it works as intended. Unit testing is an important step in the development process because if done correctly, it can help detect early flaws in code which may be more difficult to find in later testing stages. The unit test plays a role in improving the manageability like:

• Tests Reduce Bugs in New Features
• Tests Reduce Bugs in Existing Features
• Tests Are Good Documentation
• Tests Reduce the Cost of Change
• Tests Allow Refactoring
• Tests Constrain Features
• Tests Defend Against Other Programmers
• Testing Makes Development Faster

For creating Unit Tests don’t forget you’ll find the Unit Test in app/code/[Vendor]/[ModuleName]/Unit/Test

How to run Magento Open Source Unit Test?

In the below example of helper the unitTest function is defined which returns some value. We are going to test it through Unit Test.

<?php
namespace Webkul\UnitTest\Helper;

use Magento\Store\Model\StoreManagerInterface;

class Data extends \Magento\Framework\App\Helper\AbstractHelper
{
    /**
     * @var StoreManagerInterface
     */
    protected $storeManager;

    /**
     * @var \Magento\Framework\App\Helper\Context
     */
    protected $context;

    /**
     * __construct function
     *
     * @param StoreManagerInterface $storeManager
     * @param \Magento\Framework\App\Helper\Context $context
     */
    public function __construct(
        StoreManagerInterface $storeManager,
        \Magento\Framework\App\Helper\Context $context
    ) {
        parent::__construct($context);
        $this->storeManager = $storeManager;
    }
    
    /**
     * Unit Test method
     *
     * @return string
     */
    public function unitTest()
    {
        return __("This is Unit Test");
    }
}

Create a Unit Test file: app/code/Webkul/UnitTest/Test/Unit/Helper/DataTest.php

<?php
namespace Webkul\UnitTest\Test\Unit\Helper;

use Webkul\UnitTest\Helper\Data;
use Magento\Store\Model\StoreManagerInterface;
use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;

class DataTest extends \PHPUnit\Framework\TestCase
{
    /**
     * @var StoreManagerInterface
     */
    protected $storeManager;

    /**
     * @var \Magento\Framework\App\Helper\Context
     */
    protected $context;

    protected $expectedMessage;

    /**
     * Set up
     *
     * @return void
     */
    protected function setUp(): void
    {
        $objectManager = new ObjectManager($this);

        $this->context = $this->createMock(
            \Magento\Framework\App\Helper\Context::class
        );

        $this->storeManager = $this->getMockForAbstractClass(
            StoreManagerInterface::class
        );

        /* Mock Class Object With Constructor Args*/
        $this->helper = $objectManager->getObject(
            Data::class,
            [
               "context" => $this->context,
               "storeManager" => $this->storeManager
            ]
        );
    }

    /**
     * Test unitTest function
     */
    public function testUnitTest()
    {
        $this->expectedMessage = __("This is Unit Test")
        $this->assertEquals($this->expectedMessage, $this->helper->unitTest());
        // Optionally
        $this->assertTrue(true);
    }
}

Running Unit Tests in the CLI

For running all Unit Tests

vendor/bin/phpunit -c dev/tests/unit/phpunit.xml.dist

Running only a subset of the unit tests

To run only tests within a specific directory branch, all you have to do is to specify the directory branch after the command.

vendor/bin/phpunit -c dev/tests/unit/phpunit.xml.dist          app/code/Webkul/UnitTest/Test/Unit/

You’ll run the above command from Magento Open Source root then it will display the test result.

PHPUnit 9.5.20

...........                                                                                                                        1 / 1 (100%)

Time: 00:00.171, Memory: 34.00 MB

OK (1 tests, 1 assertions)

This is the basic introduction to Unit Testing in Magento Open Source and Adobe Commerce. In the next blogs we will discuss the below points:

• Object Mocking Techniques.
• How to use methods of the mocked objects.
• Assertions.
• How to use data providers in Unit Testing.
• How to prevent object manager in Unit Testing.

Thank’s for reading this. If you have any queries please comment below.