How to use PHPUnit for regression testing in PHP development

With the rapid development of web applications, PHP has become a widely used programming language. As PHP programmers, we need to ensure that our code can run normally, especially after multiple developments and modifications. This is the purpose of regression testing - to ensure that updating or modifying the code does not negatively impact existing functionality. PHPUnit is one of the most popular testing frameworks in PHP and it is the best choice for unit testing. In this article, we will learn about the PHPUnit framework and its application in PHP development.

What is PHPUnit?

PHPUnit is a testing framework based on the xUnit architecture developed by Sebastian Bergmann, which can be used to test units and functions in PHP applications. It supports PHPUnit Mock Objects, which allows us to easily test code that depends on other objects or resources. PHPUnit provides powerful features to help us write more robust applications faster.

Installing PHPUnit

Before starting the PHPUnit test, we need to install it first. PHPUnit can be installed manually or through Composer. Composer is a dependency manager that helps us download and install PHPUnit and other necessary files. To install PHPUnit, use the following command:

$ composer require --dev phpunit/phpunit ^9.5

This will install PHPUnit in the dev environment of the test application.

Writing PHPUnit tests

PHPUnit tests usually have three parts: preparing test code, running the test, and viewing the test results. To write PHPUnit tests, we need to create a class and name it according to certain rules. This class should extend PHPUnitFrameworkTestCase class. Each method in the class should correspond to a test case, which we call a test method. The test method name must start with test and the parameters are empty. Next, let's look at an example:

use PHPUnitFrameworkTestCase;

class MathTest extends TestCase
{
    public function testAddition()
    {
        $this->assertEquals(2+2, 4);
    }

    public function testSubtraction()
    {
        $this->assertEquals(5-3, 2);
    }
}

In the above example, we defined a MathTest test class and wrote two test methods inside it to test addition and subtraction respectively. The test method uses the assertion assertEquals() provided by PHPUnit, which compares whether two values ​​are equal. If equal, the test passes, otherwise the test fails.

Run the PHPUnit test

After writing the PHPUnit test, we can run the test. We can use the following command line command to execute the test:

$ ./vendor/bin/phpunit tests/

The above command executes all test cases in the tests directory (you can also specify a test file). If all tests pass we should see a green message "OK", otherwise we will see a failure message in red. We can also add the "--verbose" flag to the command line to get more verbose test output.

PHPUnit is a powerful testing framework that can be used to test various types of units and functions in PHP applications. By using PHPUnit, we can ensure that our code will work properly and that modifications to the code will not negatively impact existing functionality. Hope this article helps you understand how to use PHPUnit for regression testing.

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