diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index f363898..fcc7247 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-versions: ['7.4', '8.0', '8.1', '8.2', '8.3', '8.4', '8.5']
+        php-versions: ['8.2', '8.3', '8.4', '8.5']
     steps:
     - uses: actions/checkout@v2
 
@@ -43,8 +43,5 @@ jobs:
     - name: PHPStan
       run: bin/phpstan
 
-    - name: Composer validate
-      run: composer validate
-
- #   - name: Infection
-#      run: bin/infection --formatter=progress
+    - name: Infection
+      run: bin/infection --formatter=progress
diff --git a/composer.json b/composer.json
index fda8381..823bde7 100644
--- a/composer.json
+++ b/composer.json
@@ -20,20 +20,23 @@
         }
     },
     "require": {
-        "php": ">=7.4|^8.0",
+        "php": ">=8.2",
         "webmozart/assert": "^1.0",
-        "symfony/event-dispatcher": "^4.0|^5.0|^6.0|^7.0"
+        "symfony/event-dispatcher": "^7.0||^8.0"
     },
     "require-dev": {
         "ext-pdo": "*",
-        "doctrine/annotations": "^1.13",
-        "doctrine/orm": "^2.5",
+        "doctrine/orm": ">=2.5",
         "infection/infection": "~0.13",
         "phpstan/phpstan": "^2.0",
         "phpstan/phpstan-phpunit": "^2.0",
-        "phpunit/phpunit": "^10.0|^11.0|^12.0",
+        "phpunit/phpunit": "^12.0",
         "squizlabs/php_codesniffer": "^3.2",
-        "symfony/cache": "^4.0|^5.0|^6.0"
+        "symfony/cache": ">=7.0",
+        "symfony/var-exporter": "^7.0"
+    },
+    "scripts": {
+        "test": "bin/phpunit; bin/phpcs; bin/phpstan; bin/infection"
     },
     "config": {
         "bin-dir": "bin",
diff --git a/examples/ContextUsingBuilderTest.php b/examples/ContextUsingBuilderTest.php
index 848ebbc..1951dd7 100644
--- a/examples/ContextUsingBuilderTest.php
+++ b/examples/ContextUsingBuilderTest.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State\Example;
 
diff --git a/examples/DoctrineMappedContextTest.php b/examples/DoctrineMappedContextTest.php
index 65c9e8a..ff3759c 100644
--- a/examples/DoctrineMappedContextTest.php
+++ b/examples/DoctrineMappedContextTest.php
@@ -2,16 +2,12 @@
 
 namespace Star\Component\State\Example;
 
+use Doctrine\DBAL\DriverManager;
 use Doctrine\ORM\EntityManager;
 use Doctrine\ORM\EntityManagerInterface;
-use Doctrine\ORM\Mapping\Column;
-use Doctrine\ORM\Mapping\Embedded;
-use Doctrine\ORM\Mapping\Embeddable;
-use Doctrine\ORM\Mapping\Entity;
-use Doctrine\ORM\Mapping\GeneratedValue;
-use Doctrine\ORM\Mapping\Id;
+use Doctrine\ORM\Mapping as ORM;
+use Doctrine\ORM\ORMSetup;
 use Doctrine\ORM\Tools\SchemaTool;
-use Doctrine\ORM\Tools\Setup;
 use PHPUnit\Framework\AssertionFailedError;
 use PHPUnit\Framework\TestCase;
 use Star\Component\State\Builder\StateBuilder;
@@ -27,14 +23,15 @@ public function setUp(): void
             $this->markTestSkipped('Sqlite extension is needed');
         }
 
-        $configuration = Setup::createAnnotationMetadataConfiguration([__DIR__], true);
-        $this->em = EntityManager::create(
+        $configuration = ORMSetup::createAttributeMetadataConfiguration([__DIR__], true);
+        $connection = DriverManager::getConnection(
             [
                 'driver' => 'pdo_sqlite',
                 'in_memory' => true,
             ],
-            $configuration
+            $configuration,
         );
+        $this->em = new EntityManager($connection, $configuration);
         $tool = new SchemaTool($this->em);
         $tool->createSchema([$this->em->getClassMetadata(MyEntity::class)]);
     }
@@ -82,24 +79,16 @@ private function save(MyEntity $entity): MyEntity
     }
 }
 
-/**
- * @Entity()
- */
+#[ORM\Entity]
 class MyEntity
 {
-    /**
-     * @var int
-     * @Id()
-     * @GeneratedValue(strategy="AUTO")
-     * @Column(name="id", type="integer")
-     */
+    #[ORM\Id()]
+    #[ORM\GeneratedValue(strategy: "AUTO")]
+    #[ORM\Column(name: "id", type: "integer")]
     public int $id;
 
-    /**
-     * @var MyState|StateMetadata
-     * @Embedded(class="MyState", columnPrefix="my_")
-     */
-    private $state;
+    #[ORM\Embedded(class: "MyState", columnPrefix: "my_")]
+    private MyState $state;
 
     public function __construct()
     {
@@ -122,15 +111,10 @@ public function unlock(): void
     }
 }
 
-/**
- * @Embeddable()
- */
+#[ORM\Embeddable]
 final class MyState extends StateMetadata
 {
-    /**
-     * @var string
-     * @Column(name="state", type="string")
-     */
+    #[ORM\Column(name: "state", type: "string")]
     protected string $current;
 
     public function __construct()
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 63df743..6dc3d51 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -2,6 +2,7 @@
 <ruleset>
     <rule ref="PSR2" />
     <arg name="colors" />
+    <arg value="p" />
 
     <file>src</file>
     <file>examples</file>
diff --git a/src/Builder/StateBuilder.php b/src/Builder/StateBuilder.php
index 3033e4a..dbc9ca1 100644
--- a/src/Builder/StateBuilder.php
+++ b/src/Builder/StateBuilder.php
@@ -9,6 +9,7 @@
 use Star\Component\State\TransitionRegistry;
 use Star\Component\State\Transitions\ManyToOneTransition;
 use Star\Component\State\Transitions\OneToOneTransition;
+use function is_array;
 
 /**
  * Tool to build the StateMachine.
@@ -16,12 +17,22 @@
 final class StateBuilder
 {
     private TransitionRegistry $registry;
-    private EventRegistry $listeners;
+    private EventRegistry /* todo use StateRegistry */ $listeners;
 
-    public function __construct()
-    {
-        $this->registry = new TransitionRegistry();
-        $this->listeners = new EventDispatcherAdapter();
+    public function __construct(
+        ?TransitionRegistry $registry = null,
+        ?EventRegistry $listeners = null,
+    ) {
+        /** @todo deprecated nullable construct, move to private */
+        if (!$registry) {
+            $registry = new TransitionRegistry();
+        }
+        $this->registry = $registry;
+
+        if (!$listeners) {
+            $listeners = new EventDispatcherAdapter();
+        }
+        $this->listeners = $listeners;
     }
 
     /**
@@ -31,9 +42,9 @@ public function __construct()
      *
      * @return StateBuilder
      */
-    public function allowTransition(string $name, $from, string $to): StateBuilder
+    public function allowTransition(string $name, string|array $from, string $to): StateBuilder
     {
-        if (\is_array($from)) {
+        if (is_array($from)) {
             $transition = new ManyToOneTransition($name, $to, ...$from);
         } else {
             $transition = new OneToOneTransition($name, $from, $to);
@@ -49,6 +60,7 @@ public function allowTransition(string $name, $from, string $to): StateBuilder
      */
     public function allowCustomTransition(StateTransition $transition): void
     {
+        // todo add interface for registry, and inject interface instead
         $this->registry->addTransition($transition);
     }
 
@@ -58,7 +70,7 @@ public function allowCustomTransition(StateTransition $transition): void
      *
      * @return StateBuilder
      */
-    public function addAttribute(string $attribute, $states): StateBuilder
+    public function addAttribute(string $attribute, string|array $states): StateBuilder
     {
         $states = (array) $states;
         foreach ($states as $stateName) {
@@ -73,8 +85,10 @@ public function create(string $currentState): StateMachine
         return new StateMachine($currentState, $this->registry, $this->listeners);
     }
 
-    public static function build(): StateBuilder
-    {
-        return new static();
+    public static function build(
+        ?TransitionRegistry $registry = null,
+        ?EventRegistry $listeners = null,
+    ): StateBuilder {
+        return new self($registry, $listeners);
     }
 }
diff --git a/src/Callbacks/BufferStateChanges.php b/src/Callbacks/BufferStateChanges.php
new file mode 100644
index 0000000..94e36a6
--- /dev/null
+++ b/src/Callbacks/BufferStateChanges.php
@@ -0,0 +1,51 @@
+<?php declare(strict_types=1);
+
+namespace Star\Component\State\Callbacks;
+
+use RuntimeException;
+use Star\Component\State\InvalidStateTransitionException;
+use Star\Component\State\StateMachine;
+use Webmozart\Assert\Assert;
+use function get_class;
+use function is_object;
+
+final class BufferStateChanges implements TransitionCallback
+{
+    /**
+     * @var array<string, list<string>>
+     */
+    private array $buffer = [];
+
+    public function beforeStateChange($context, StateMachine $machine): void
+    {
+        if (is_object($context)) {
+            $context = get_class($context);
+        }
+        Assert::string($context, 'Context is expected to be a string. Got: %s');
+
+        $this->buffer[$context][] = __FUNCTION__;
+    }
+
+    public function afterStateChange($context, StateMachine $machine): void
+    {
+        if (is_object($context)) {
+            $context = get_class($context);
+        }
+        Assert::string($context, 'Context is expected to be a string. Got: %s');
+
+        $this->buffer[$context][] = __FUNCTION__;
+    }
+
+    public function onFailure(InvalidStateTransitionException $exception, $context, StateMachine $machine): string
+    {
+        throw new RuntimeException(__METHOD__ . ' is not implemented yet.');
+    }
+
+    /**
+     * @return array<string, list<string>>
+     */
+    public function flushBuffer(): array
+    {
+        return $this->buffer;
+    }
+}
diff --git a/src/Event/StateEventStore.php b/src/Event/StateEventStore.php
index 197b5db..18929b3 100644
--- a/src/Event/StateEventStore.php
+++ b/src/Event/StateEventStore.php
@@ -1,12 +1,11 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State\Event;
 
+use InvalidArgumentException;
+use function get_class;
+use function sprintf;
+
 final class StateEventStore
 {
     /**
@@ -29,4 +28,20 @@ final class StateEventStore
      * @see TransitionWasFailed
      */
     const FAILURE_TRANSITION = 'star_state.transition_failure';
+
+    public static function eventNameFromClass(StateEvent $event): string
+    {
+        // todo deprecate string event in favor of class name
+        return match (get_class($event)) {
+            TransitionWasRequested::class => self::BEFORE_TRANSITION,
+            TransitionWasSuccessful::class => self::AFTER_TRANSITION,
+            TransitionWasFailed::class => self::FAILURE_TRANSITION,
+            default => throw new InvalidArgumentException(
+                sprintf(
+                    'Event "%s" is not mapped to a name.',
+                    get_class($event),
+                )
+            ),
+        };
+    }
 }
diff --git a/src/Event/TransitionWasRequested.php b/src/Event/TransitionWasRequested.php
index 06c62f0..9b93983 100644
--- a/src/Event/TransitionWasRequested.php
+++ b/src/Event/TransitionWasRequested.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State\Event;
 
diff --git a/src/Event/TransitionWasSuccessful.php b/src/Event/TransitionWasSuccessful.php
index 7ef6ef9..24be7dd 100644
--- a/src/Event/TransitionWasSuccessful.php
+++ b/src/Event/TransitionWasSuccessful.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State\Event;
 
diff --git a/src/InvalidStateTransitionException.php b/src/InvalidStateTransitionException.php
index e7f6fd0..49d5c31 100644
--- a/src/InvalidStateTransitionException.php
+++ b/src/InvalidStateTransitionException.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
diff --git a/src/NotFoundException.php b/src/NotFoundException.php
index bdb00a0..e4c5c21 100644
--- a/src/NotFoundException.php
+++ b/src/NotFoundException.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
diff --git a/src/Port/Symfony/EventDispatcherAdapter.php b/src/Port/Symfony/EventDispatcherAdapter.php
index f4fc6b9..5a644dd 100644
--- a/src/Port/Symfony/EventDispatcherAdapter.php
+++ b/src/Port/Symfony/EventDispatcherAdapter.php
@@ -3,6 +3,7 @@
 namespace Star\Component\State\Port\Symfony;
 
 use Star\Component\State\Event\StateEvent;
+use Star\Component\State\Event\StateEventStore;
 use Star\Component\State\EventRegistry;
 use Symfony\Component\EventDispatcher\EventDispatcher;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
@@ -22,7 +23,7 @@ public function __construct(
 
     public function dispatch(string $name, StateEvent $event): void
     {
-        $this->dispatcher->dispatch($event);
+        $this->dispatcher->dispatch($event, StateEventStore::eventNameFromClass($event));
     }
 
     public function addListener(string $event, callable $listener): void
diff --git a/src/StateMachine.php b/src/StateMachine.php
index 16748c3..19eeb38 100644
--- a/src/StateMachine.php
+++ b/src/StateMachine.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
@@ -45,6 +40,7 @@ public function transit(
         mixed $context,
         ?TransitionCallback $callback = null
     ): string {
+        // todo deprecate mixed to use StateContext
         if (!$callback) {
             $callback = new AlwaysThrowExceptionOnFailure();
         }
diff --git a/src/StateTransition.php b/src/StateTransition.php
index db6de73..b396a56 100644
--- a/src/StateTransition.php
+++ b/src/StateTransition.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
diff --git a/src/TransitionRegistry.php b/src/TransitionRegistry.php
index 609c8b0..9b08912 100644
--- a/src/TransitionRegistry.php
+++ b/src/TransitionRegistry.php
@@ -1,13 +1,13 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
 use Star\Component\State\Transitions\ReadOnlyTransition;
+use function array_key_exists;
+use function array_map;
+use function array_merge;
+use function array_unique;
+use function in_array;
 
 final class TransitionRegistry implements StateRegistry
 {
@@ -62,10 +62,10 @@ public function addAttribute(string $state, string $attribute): void
     {
         $attributes = [$attribute];
         if ($this->hasState($state)) {
-            $attributes = \array_merge($this->states[$state], $attributes);
+            $attributes = array_merge($this->states[$state], $attributes);
         }
 
-        $this->states[$state] = \array_unique($attributes);
+        $this->states[$state] = array_unique($attributes);
     }
 
     /**
@@ -74,7 +74,7 @@ public function addAttribute(string $state, string $attribute): void
      */
     private function addAttributes(string $state, array $attributes): void
     {
-        \array_map(
+        array_map(
             function ($attribute) use ($state) {
                 $this->addAttribute($state, $attribute);
             },
@@ -89,7 +89,7 @@ public function transitionStartsFrom(string $transition, string $state): bool
             $from = $this->transitions[$transition]['from'];
         }
 
-        return \in_array($state, $from, true); // @phpstan-ignore-line
+        return in_array($state, $from, true); // @phpstan-ignore-line
     }
 
     public function hasAttribute(string $state, string $attribute): bool
@@ -98,12 +98,12 @@ public function hasAttribute(string $state, string $attribute): bool
             return false;
         }
 
-        return \in_array($attribute, $this->states[$state]);
+        return in_array($attribute, $this->states[$state]);
     }
 
     public function hasState(string $name): bool
     {
-        return \array_key_exists($name, $this->states);
+        return array_key_exists($name, $this->states);
     }
 
     public function acceptTransitionVisitor(TransitionVisitor $visitor): void
diff --git a/src/Visitor/AttributeDumper.php b/src/Visitor/AttributeDumper.php
index 9d237dc..53f212b 100644
--- a/src/Visitor/AttributeDumper.php
+++ b/src/Visitor/AttributeDumper.php
@@ -8,16 +8,16 @@ final class AttributeDumper implements StateVisitor
 {
     /**
      * An array having the state name as key and the attributes of this state.
-     * @var string[][]
+     * @var array<string, string[]>
      */
-    private array $structure = [];
+    private array $attributesByStates = [];
 
     /**
-     * @return string[][]
+     * @return array<string, string[]>
      */
     public function getStructure(): array
     {
-        return $this->structure;
+        return $this->attributesByStates;
     }
 
     /**
@@ -26,10 +26,6 @@ public function getStructure(): array
      */
     public function visitState(string $name, array $attributes): void
     {
-        if (!isset($this->structure[$name])) {
-            $this->structure[$name] = [];
-        }
-
-        $this->structure[$name] = array_unique(array_merge($this->structure[$name], $attributes));
+        $this->attributesByStates[$name] = $attributes;
     }
 }
diff --git a/tests/Callbacks/BufferStateChangesTest.php b/tests/Callbacks/BufferStateChangesTest.php
new file mode 100644
index 0000000..18ace69
--- /dev/null
+++ b/tests/Callbacks/BufferStateChangesTest.php
@@ -0,0 +1,84 @@
+<?php declare(strict_types=1);
+
+namespace Star\Component\State\Callbacks;
+
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+use Star\Component\State\Builder\StateBuilder;
+
+class BufferStateChangesTest extends TestCase
+{
+    public function test_it_should_buffer_context_as_object(): void
+    {
+        $buffer = new BufferStateChanges();
+        $machine = StateBuilder::build()
+            ->create('');
+
+        $buffer->beforeStateChange(
+            (object) [],
+            $machine
+        );
+        $buffer->afterStateChange(
+            (object) [],
+            $machine
+        );
+
+        self::assertSame(
+            [
+                'stdClass' => [
+                    0 => 'beforeStateChange',
+                    1 => 'afterStateChange',
+                ],
+            ],
+            $buffer->flushBuffer(),
+        );
+    }
+
+    public function test_it_should_buffer_context_as_string(): void
+    {
+        $buffer = new BufferStateChanges();
+        $machine = StateBuilder::build()
+            ->create('');
+
+        $buffer->beforeStateChange(
+            'stdClass',
+            $machine
+        );
+        $buffer->afterStateChange(
+            'stdClass',
+            $machine
+        );
+
+        self::assertSame(
+            [
+                'stdClass' => [
+                    0 => 'beforeStateChange',
+                    1 => 'afterStateChange',
+                ],
+            ],
+            $buffer->flushBuffer(),
+        );
+    }
+
+    public function test_it_should_not_allow_non_string_context_in_before(): void
+    {
+        $buffer = new BufferStateChanges();
+        $machine = StateBuilder::build()
+            ->create('');
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Context is expected to be a string. Got: integer');
+        $buffer->beforeStateChange(42, $machine);
+    }
+
+    public function test_it_should_not_allow_non_string_context_in_after(): void
+    {
+        $buffer = new BufferStateChanges();
+        $machine = StateBuilder::build()
+            ->create('');
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Context is expected to be a string. Got: integer');
+        $buffer->afterStateChange(42, $machine);
+    }
+}
diff --git a/tests/Event/StateEventStoreTest.php b/tests/Event/StateEventStoreTest.php
new file mode 100644
index 0000000..1d651b0
--- /dev/null
+++ b/tests/Event/StateEventStoreTest.php
@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace Star\Component\State\Event;
+
+use InvalidArgumentException;
+use PHPUnit\Framework\TestCase;
+
+class StateEventStoreTest extends TestCase
+{
+    public function test_it_should_throw_exception_when_invalid_event(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('is not mapped to a name.');
+        StateEventStore::eventNameFromClass($this->createStub(StateEvent::class));
+    }
+}
diff --git a/tests/StateBuilderTest.php b/tests/StateBuilderTest.php
index 5a9c854..e4ee0c4 100644
--- a/tests/StateBuilderTest.php
+++ b/tests/StateBuilderTest.php
@@ -4,6 +4,8 @@
 
 use PHPUnit\Framework\TestCase;
 use Star\Component\State\Builder\StateBuilder;
+use Star\Component\State\Event\StateEventStore;
+use Star\Component\State\Port\Symfony\EventDispatcherAdapter;
 
 final class StateBuilderTest extends TestCase
 {
@@ -34,4 +36,29 @@ public function test_it_should_return_whether_the_current_state_has_attribute_af
         self::assertTrue($machine->isInState('to'));
         self::assertFalse($machine->hasAttribute('attr'));
     }
+
+    public function test_it_should_dispatch_event_on_transit(): void
+    {
+        $i = 0;
+        $addition = function () use (&$i): void {
+            $i ++;
+        };
+
+        $listeners = new EventDispatcherAdapter();
+        $listeners->addListener(
+            StateEventStore::BEFORE_TRANSITION,
+            $addition
+        );
+        $listeners->addListener(
+            StateEventStore::AFTER_TRANSITION,
+            $addition
+        );
+
+        $machine = StateBuilder::build(listeners: $listeners)
+            ->allowTransition('t', 'from', 'to')
+            ->create('from');
+
+        $machine->transit('t', 'c');
+        self::assertSame(2, $i);
+    }
 }
diff --git a/tests/StateMachineTest.php b/tests/StateMachineTest.php
index 07d134e..203ecb4 100644
--- a/tests/StateMachineTest.php
+++ b/tests/StateMachineTest.php
@@ -1,13 +1,10 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
 use PHPUnit\Framework\TestCase;
+use Star\Component\State\Callbacks\BufferStateChanges;
+use Star\Component\State\Callbacks\TransitionCallback;
 use Star\Component\State\Event\StateEventStore;
 use Star\Component\State\Event\TransitionWasFailed;
 use Star\Component\State\Event\TransitionWasSuccessful;
@@ -102,14 +99,15 @@ public function test_state_can_have_attribute(): void
 
     public function test_it_should_visit_the_transitions(): void
     {
-        $registry = $this->createMock(StateRegistry::class);
-        $machine = new StateMachine('', $registry, $this->events);
         $visitor = $this->createStub(TransitionVisitor::class);
-
+        $registry = $this->createMock(StateRegistry::class);
         $registry
             ->expects($this->once())
             ->method('acceptTransitionVisitor')
             ->with($visitor);
+
+        $machine = new StateMachine('', $registry, $this->events);
+
         $machine->acceptTransitionVisitor($visitor);
     }
 
@@ -136,4 +134,31 @@ public function test_it_should_dispatch_an_event_before_a_transition_has_failed(
         self::assertCount(1, $events);
         self::assertContainsOnlyInstancesOf(TransitionWasFailed::class, $events);
     }
+
+    public function test_it_should_invoke_before_state_change_callback(): void
+    {
+        $this->registry->addTransition(new OneToOneTransition('t', 'current', 'to'));
+        $buffer = new BufferStateChanges();
+
+        self::assertSame(
+            [],
+            $buffer->flushBuffer(),
+        );
+
+        $this->machine->transit(
+            't',
+            'context',
+            $buffer,
+        );
+
+        self::assertSame(
+            [
+                'context' => [
+                    'beforeStateChange',
+                    'afterStateChange',
+                ],
+            ],
+            $buffer->flushBuffer(),
+        );
+    }
 }
diff --git a/tests/TestContext.php b/tests/TestContext.php
index 2543164..a6f33ef 100644
--- a/tests/TestContext.php
+++ b/tests/TestContext.php
@@ -1,9 +1,4 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
diff --git a/tests/TransitionRegistryTest.php b/tests/TransitionRegistryTest.php
index b62a211..1d4bab2 100644
--- a/tests/TransitionRegistryTest.php
+++ b/tests/TransitionRegistryTest.php
@@ -1,15 +1,11 @@
 <?php declare(strict_types=1);
-/**
- * This file is part of the php-state project.
- *
- * (c) Yannick Voyer (http://github.com/yvoyer)
- */
 
 namespace Star\Component\State;
 
 use PHPUnit\Framework\TestCase;
 use Star\Component\State\Transitions\ManyToOneTransition;
 use Star\Component\State\Transitions\OneToOneTransition;
+use Star\Component\State\Visitor\AttributeDumper;
 
 final class TransitionRegistryTest extends TestCase
 {
@@ -147,4 +143,25 @@ public function visitState(string $name, array $attributes): void
             $visitor->attributes
         );
     }
+
+    public function test_it_should_add_unique_attributes(): void
+    {
+        $this->registry->addAttribute('a', '1');
+        $this->registry->addAttribute('a', '2');
+        $this->registry->addAttribute('a', '2');
+        $this->registry->addAttribute('a', '3');
+        $this->registry->addAttribute('a', '3');
+
+        $this->registry->acceptStateVisitor($visitor = new AttributeDumper());
+        self::assertSame(
+            [
+                'a' => [
+                    '1',
+                    '2',
+                    '3',
+                ],
+            ],
+            $visitor->getStructure()
+        );
+    }
 }
diff --git a/tests/Visitor/AttributeDumperTest.php b/tests/Visitor/AttributeDumperTest.php
index 10d041c..54476b5 100644
--- a/tests/Visitor/AttributeDumperTest.php
+++ b/tests/Visitor/AttributeDumperTest.php
@@ -4,25 +4,19 @@
 
 use PHPUnit\Framework\TestCase;
 use Star\Component\State\Builder\StateBuilder;
-use Star\Component\State\StateMachine;
 
 final class AttributeDumperTest extends TestCase
 {
-    private StateMachine $machine;
-
-    public function setUp(): void
+    public function test_it_should_dump_the_attributes(): void
     {
-        $this->machine = StateBuilder::build()
+        $machine = StateBuilder::build()
             ->allowTransition('t1', 's1', 's2')
             ->allowTransition('t2', ['s2', 's3'], 's1')
             ->addAttribute('a1', 's1')
             ->addAttribute('a2', ['s1', 's2'])
             ->create('s1');
-    }
+        $machine->acceptStateVisitor($dumper = new AttributeDumper());
 
-    public function test_it_should_dump_the_attributes(): void
-    {
-        $this->machine->acceptStateVisitor($dumper = new AttributeDumper());
         self::assertEquals(
             [
                 's1' => ['a1', 'a2'],
@@ -32,4 +26,24 @@ public function test_it_should_dump_the_attributes(): void
             $dumper->getStructure()
         );
     }
+
+    public function test_it_should_dump_unique_attributes_by_state(): void
+    {
+        $machine = StateBuilder::build()
+            ->allowTransition('t1', 's1', 's2')
+            ->addAttribute('a1', ['s1', 's2'])
+            ->addAttribute('a2', ['s1', 's2'])
+            ->addAttribute('a3', ['s1', 's2'])
+            ->addAttribute('a4', ['s1', 's2'])
+            ->create('s1');
+        $machine->acceptStateVisitor($dumper = new AttributeDumper());
+
+        self::assertEquals(
+            [
+                's1' => ['a1', 'a2', 'a3', 'a4'],
+                's2' => ['a1', 'a2', 'a3', 'a4'],
+            ],
+            $dumper->getStructure()
+        );
+    }
 }