Extending PHPUnit

Subclass PHPUnit\Framework\TestCase

Write custom assertions and utility methods in an abstract subclass of PHPUnit\Framework\TestCase and derive your test case classes from that class. This is one of the easiest ways to extend PHPUnit.

Write custom assertions

When writing custom assertions it is the best practice to follow how PHPUnit’s own assertions are implemented. As you can see in Example 11.1, the assertTrue() method is a wrapper around the isTrue() and assertThat() methods: isTrue() creates a matcher object that is passed on to assertThat() for evaluation.

<?php declare(strict_types=1);
namespace PHPUnit\Framework;

use PHPUnit\Framework\Constraint\IsTrue;

abstract class Assert
{
    // ...

    public static function assertTrue($condition, string $message = ''): void
    {
        static::assertThat($condition, static::isTrue(), $message);
    }

    // ...

    public static function isTrue(): IsTrue
    {
        return new IsTrue;
    }

    // ...
}

Example 11.2 shows how PHPUnit\Framework\Constraint\IsTrue extends the abstract base class for matcher objects (or constraints), PHPUnit\Framework\Constraint.

<?php declare(strict_types=1);
namespace PHPUnit\Framework\Constraint;

use PHPUnit\Framework\Constraint;

final class IsTrue extends Constraint
{
    public function toString(): string
    {
        return 'is true';
    }

    protected function matches($other): bool
    {
        return $other === true;
    }
}

The effort of implementing the assertTrue() and isTrue() methods as well as the PHPUnit\Framework\Constraint\IsTrue class yields the benefit that assertThat() automatically takes care of evaluating the assertion and bookkeeping tasks such as counting it for statistics. Furthermore, the isTrue() method can be used as a matcher when configuring mock objects.

Extending the TestRunner

PHPUnit’s test runner can be extended by registering objects that implement one or more of the following interfaces:

• AfterIncompleteTestHook
• AfterLastTestHook
• AfterRiskyTestHook
• AfterSkippedTestHook
• AfterSuccessfulTestHook
• AfterTestErrorHook
• AfterTestFailureHook
• AfterTestWarningHook
• AfterTestHook
• BeforeFirstTestHook
• BeforeTestHook

Each “hook”, meaning each of the interfaces listed above, represents an event that can occur while the tests are being executed.

See The <extensions> Element for details on how to register extensions in PHPUnit’s XML configuration.

Example 11.3 shows an example for an extension implementing BeforeFirstTestHook and AfterLastTestHook:

<?php declare(strict_types=1);
namespace Vendor;

use PHPUnit\Runner\BeforeFirstTestHook;
use PHPUnit\Runner\AfterLastTestHook;

final class MyExtension implements BeforeFirstTestHook, AfterLastTestHook
{
    public function executeBeforeFirstTest(): void
    {
        // called before the first test is being run
    }

    public function executeAfterLastTest(): void
    {
        // called after the last test has been run
    }
}

<?php declare(strict_types=1);
namespace Vendor;

use PHPUnit\Runner\BeforeFirstTestHook;
use PHPUnit\Runner\AfterLastTestHook;

final class MyConfigurableExtension implements BeforeFirstTestHook, AfterLastTestHook
{
    protected $config_value_1 = '';

    protected $config_value_2 = 0;

    public function __construct(string $value1 = '', int $value2 = 0)
    {
        $this->config_value_1 = $config_1;
        $this->config_value_2 = $config_2;
    }

    public function executeBeforeFirstTest(): void
    {
        if (strlen($this-config_value_1) {
            echo 'Testing with configuration value: ' . $this->config_value_1;
        }
    }

    public function executeAfterLastTest(): void
    {
        if ($this->config_value_2 > 10) {
            echo 'Second config value is OK!';
        }
    }
}

<extensions>
    <extension class="Vendor\MyUnconfigurableExtension" />
    <extension class="Vendor\MyConfigurableExtension">
        <arguments>
            <string>Hello world!</string>
            <int>15</int>
        </arguments>
    </extension>
</extensions>