How to use PHPUnit for code coverage testing in PHP development

For PHP developers, using PHPUnit for code coverage testing is a very important task. Code coverage testing can help developers check whether there are untested parts of the code they write and whether the test coverage is high enough. This article will introduce how to use PHPUnit for code coverage testing.

First, we need to install PHPUnit. Composer can be used to install PHPUnit:

composer require --dev phpunit/phpunit

After the installation is complete, we can run the following command in the terminal to check whether PHPUnit has been successfully installed:

php vendor/bin/phpunit --version

Next, we need to configure it before running the test PHPUnit. Create a phpunit.xml file in the root directory of the project with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<phpunit backupGlobals="false"
         backupStaticAttributes="false"
         colors="true"
         convertErrorsToExceptions="true"
         convertNoticesToExceptions="true"
         convertWarningsToExceptions="true"
         processIsolation="false"
         stopOnFailure="false">
    <testsuites>
        <testsuite name="Example Test Suite">
            <directory>tests</directory>
        </testsuite>
    </testsuites>
    <filter>
        <whitelist processUncoveredFilesFromWhitelist="true">
            <directory suffix=".php">src</directory>
        </whitelist>
    </filter>
</phpunit>

This configuration file tells PHPUnit which files should be included when running tests, and also configures some errors during test runs.

Before we write the test code, let's take a look at a simple example below:

<?php

class Foo
{
    public function bar()
    {
        return true;
    }
}

This is a very simple PHP class that contains a public method called bar() , returns a Boolean value. Now we need to write a test for this class to make sure it behaves as expected. Create a test file in the test directory named FooTest.php with the following content:

<?php
    
use PHPUnitFrameworkTestCase;

class FooTest extends TestCase
{
    /** @test */
    public function it_should_return_true()
    {
        $foo = new Foo;
        $this->assertTrue($foo->bar());
    }
}

This test is very simple. We instantiate class Foo and make sure its bar() method returns true. Now we can run the tests and view the coverage report generated by PHPUnit. Run the following command in the terminal:

php vendor/bin/phpunit --coverage-html coverage

This command will generate an HTML coverage report and save it in the coverage directory under the project root directory. Open the report and you can see that the code coverage of class Foo is 100%. This means that the test we wrote has covered all the code of class Foo.

In general, PHPUnit is a very powerful testing tool that can help us write high-quality PHP code. Code coverage testing is a key feature of PHPUnit, ensuring that the tests we write cover every part of our code. Using PHPUnit for code coverage testing in projects can greatly improve the quality of our code and avoid some potential errors and loopholes.

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