Testing utilities

With this library you can ease the testing for your event-sourcing project when using PHPUnit. It comes with utilities for aggregates and subscribers.

Installation

composer require --dev patchlevel/event-sourcing-phpunit

Given / When / Then

Testing Aggregates

There is a special TestCase for aggregate tests which you can extend from. Extending from AggregateRootTestCase enables you to use the given / when / then notation. This makes it very clear what the test is doing. When extending the class you will need to implement a method which provides the FQCN of the aggregate you want to test.

final class ProfileTest extends AggregateRootTestCase
{
    protected function aggregateClass(): string
    {
        return Profile::class;
    }
}

When this is done, you already can start testing your behaviour. For example testing that a event is recorded.

final class ProfileTest extends AggregateRootTestCase
{ 
    // protected function aggregateClass(): string;
    
    public function testBehaviour(): void
    {
        $this
            ->given(
                new ProfileCreated(
                    ProfileId::fromString('1'),
                    Email::fromString('[email protected]'),
                ),
            )
            ->when(static fn (Profile $profile) => $profile->visitProfile(ProfileId::fromString('2')))
            ->then(new ProfileVisited(ProfileId::fromString('2')));
    }
}

You can also test multiple calls and events:

final class ProfileTest extends AggregateRootTestCase
{ 
    // protected function aggregateClass(): string;
    
    public function testBehaviour(): void
    {
        $this
            ->given(
                new ProfileCreated(
                    ProfileId::fromString('1'),
                    Email::fromString('[email protected]'),
                ),
            )
            ->when(
                static fn (Profile $profile) => $profile->visitProfile(ProfileId::fromString('2')),
                static fn (Profile $profile) => $profile->visitProfile(ProfileId::fromString('2')),
                static fn (Profile $profile) => $profile->visitProfile(ProfileId::fromString('2')),
            )
            ->then(
                new ProfileVisited(ProfileId::fromString('2')),
                new ProfileVisited(ProfileId::fromString('2')),
                new ProfileVisited(ProfileId::fromString('2')),
            );
    }
}

You can also test the creation of the aggregate:

final class ProfileTest extends AggregateRootTestCase
{ 
    // protected function aggregateClass(): string;
    
    public function testBehaviour(): void
    {
        $this
            ->when(static fn () => Profile::createProfile(ProfileId::fromString('1'), Email::fromString('[email protected]')))
            ->then(new ProfileCreated(ProfileId::fromString('1'), Email::fromString('[email protected]')));
    }
}

And expect an exception and the message of it:

final class ProfileTest extends AggregateRootTestCase
{ 
    // protected function aggregateClass(): string;
    
    public function testBehaviour(): void
    {
        $this
            ->given(
                new ProfileCreated(
                    ProfileId::fromString('1'),
                    Email::fromString('[email protected]'),
                ),
            )
            ->when(static fn (Profile $profile) => $profile->throwException())
            ->expectsException(ProfileError::class)
            ->expectsExceptionMessage('throwing so that you can catch it!');
    }
}

Testing Subscriber

For testing a subscriber there is a trait which you can use. When using SubscriberUtilities you will also be provided with a bunch of dx features which makes the testing easier. First, providing the events is the same with a given method. After that, you can call executeRun which can take multiple subscribers, which will be provided with the given events. The events will be mapped according the #[Subscribe] attribute. For our example we are taking as simplified subscriber:

use Patchlevel\EventSourcing\Attribute\Setup;
use Patchlevel\EventSourcing\Attribute\Subscribe;
use Patchlevel\EventSourcing\Attribute\Subscriber;
use Patchlevel\EventSourcing\Attribute\Teardown;

#[Subscriber('profile_subscriber', RunMode::FromBeginning)]
final class ProfileSubscriber
{
    public int $called = 0;

    #[Subscribe(ProfileCreated::class)]
    public function run(): void
    {
        $this->called++;
    }

    #[Setup]
    public function setup(): void
    {
        $this->called++;
    }

    #[Teardown]
    public function teardown(): void
    {
        $this->called++;
    }
}

With this, we can now write our test for it:

use Patchlevel\EventSourcing\Attribute\Subscriber;
use Patchlevel\EventSourcing\Subscription\RunMode;
use Patchlevel\EventSourcing\PhpUnit\Test\SubscriberUtilities;

final class ProfileSubscriberTest extends TestCase
{
    use SubscriberUtilities;

    public function testProfileCreated(): void 
    {
        $subscriber = new ProfileSubscriber(/* inject deps, if needed */);
        
        $this
            ->given(
                new ProfileCreated(
                    ProfileId::fromString('1'),
                    Email::fromString('[email protected]'),
                ),
            )
            ->executeRun($subscriber);
            
        self::assertSame(1, $subscriber->count);
    }
}

You can also test the setup and teardown methods:

use Patchlevel\EventSourcing\Attribute\Subscriber;
use Patchlevel\EventSourcing\Subscription\RunMode;
use Patchlevel\EventSourcing\PhpUnit\Test\SubscriberUtilities;

final class ProfileSubscriberTest extends TestCase
{
    use SubscriberUtilities;

    public function testSetup(): void 
    {
        $subscriber = new ProfileSubscriber(/* inject deps, if needed */);
        
        $this->executeSetup($subscriber);
            
        self::assertSame(1, $subscriber->count);
    }

    public function testTeardown(): void 
    {
        $subscriber = new ProfileSubscriber(/* inject deps, if needed */);
        
        $this->executeTeardown($subscriber);
            
        self::assertSame(1, $subscriber->count);
    }
}

Of course, you can also execute the whole workflow in one test:

use Patchlevel\EventSourcing\Attribute\Subscriber;
use Patchlevel\EventSourcing\Subscription\RunMode;
use Patchlevel\EventSourcing\PhpUnit\Test\SubscriberUtilities;

final class ProfileSubscriberTest extends TestCase
{
    use SubscriberUtilities;

    public function testProfileCreated(): void 
    {
        $subscriber = new ProfileSubscriber(/* inject deps, if needed */);
        
        $this
            ->given(
                new ProfileCreated(
                    ProfileId::fromString('1'),
                    Email::fromString('[email protected]'),
                ),
            )
            ->executeSetup($subscriber)
            ->executeRun($subscriber)
            ->executeTeardown($subscriber);
            
        self::assertSame(3, $subscriber->count);
    }
}