diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..b86e521
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,23 @@
+name: Tests
+on: [ pull_request ]
+
+jobs:
+  unit:
+    name: PHPUnit
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.4
+          coverage: none
+
+      - name: Download dependencies
+        uses: ramsey/composer-install@v2
+
+      - name: PHPUnit (unit tests)
+        run: ./vendor/bin/phpunit
diff --git a/README.md b/README.md
index 4817be1..39787f5 100644
--- a/README.md
+++ b/README.md
@@ -12,32 +12,15 @@ Via Composer
 $ composer require jongotlin/identity-number-bundle
 ```
 
-```php
-class AppKernel extends Kernel
-{
-  public function registerBundles()
-  {
-    $bundles = array(
-        // ...
-        new JGI\IdentityNumberValidatorBundle\IdentityNumberValidatorBundle(),
-    }
-  }
-}
-```
-
 ## Usage
 ```php
 use JGI\IdentityNumberValidatorBundle\Validator\Constraints as IdentityNumberAssert;
 
-/**
- * @IdentityNumberAssert\IdentityNumber(allowCoordinationNumber=true)
- */
-private $identityNumber;
+#[IdentityNumberAssert\IdentityNumber(allowCoordinationNumber=true)]
+private ?string $identityNumber;
 
-/**
- * @IdentityNumberAssert\OrganizationNumber(allowPersonalIdNumber=true, allowCoordinationNumber=true)
- */
-private $organizationNumber;
+#[IdentityNumberAssert\OrganizationNumber(allowPersonalIdNumber=true, allowCoordinationNumber=true)]
+private ?string $organizationNumber;
 ```
 
 Available options are
diff --git a/composer.json b/composer.json
index 9cdc54e..599e093 100644
--- a/composer.json
+++ b/composer.json
@@ -19,12 +19,12 @@
     }
   },
   "require": {
-    "php": "^7.0|^8.0",
-    "symfony/framework-bundle": "^2.7|^3.0|^4.0|^5.0|^6.0",
-    "byrokrat/id": "^1.0"
+    "php": "^8.2",
+    "symfony/framework-bundle": "^7.0|^8.0",
+    "byrokrat/id": "^2.1"
   },
   "require-dev": {
-    "phpunit/phpunit": "^9.5",
-    "symfony/validator": "^6.0"
+    "phpunit/phpunit": "^12.5",
+    "symfony/validator": "^8.0"
   }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 73d3304..58359ea 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -13,7 +13,7 @@
 
     <testsuites>
         <testsuite name="Project Test Suite">
-            <directory>Tests</directory>
+            <directory>tests</directory>
         </testsuite>
     </testsuites>
 
diff --git a/src/DependencyInjection/IdentityNumberValidatorExtension.php b/src/DependencyInjection/IdentityNumberValidatorExtension.php
index 612e68f..b7058a8 100644
--- a/src/DependencyInjection/IdentityNumberValidatorExtension.php
+++ b/src/DependencyInjection/IdentityNumberValidatorExtension.php
@@ -4,7 +4,7 @@
 
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\Config\FileLocator;
-use Symfony\Component\HttpKernel\DependencyInjection\Extension;
+use Symfony\Component\DependencyInjection\Extension\Extension;
 use Symfony\Component\DependencyInjection\Loader;
 
 class IdentityNumberValidatorExtension extends Extension
@@ -12,7 +12,7 @@ class IdentityNumberValidatorExtension extends Extension
     /**
      * {@inheritdoc}
      */
-    public function load(array $config, ContainerBuilder $container)
+    public function load(array $configs, ContainerBuilder $container): void
     {
         $loader = new Loader\YamlFileLoader($container, new FileLocator(__DIR__.'/../Resources/config'));
         $loader->load('services.yml');
diff --git a/src/Validator/Constraints/IdentityNumber.php b/src/Validator/Constraints/IdentityNumber.php
index c3b1bbb..8bf10ff 100644
--- a/src/Validator/Constraints/IdentityNumber.php
+++ b/src/Validator/Constraints/IdentityNumber.php
@@ -4,35 +4,26 @@
 
 use Symfony\Component\Validator\Constraint;
 
-/**
- * @Annotation
- */
+#[\Attribute]
 class IdentityNumber extends Constraint
 {
-    /**
-     * @var string
-     */
-    public $message = 'This value is not a valid identity number.';
-
-    /**
-     * @var string
-     */
-    public $messageWithCoordinationNumber = 'This value is not a valid identity number or coordination number.';
-
-    /**
-     * @var bool
-     */
-    public $allowCoordinationNumber = false;
-
-    /**
-     * @var bool
-     */
-    public $strict = false;
-
-    /**
-     * @return string
-     */
-    public function validatedBy()
+    public string $message = 'This value is not a valid identity number.';
+
+    public string $messageWithCoordinationNumber = 'This value is not a valid identity number or coordination number.';
+
+    public bool $allowCoordinationNumber = false;
+
+    public bool $strict = false;
+
+    public function __construct(?string $message = null, ?string $messageWithCoordinationNumber = null, ?bool $allowCoordinationNumber = null, ?bool $strict = null)
+    {
+        $this->message = $message ?? $this->message;
+        $this->messageWithCoordinationNumber = $messageWithCoordinationNumber ?? $this->messageWithCoordinationNumber;
+        $this->allowCoordinationNumber = $allowCoordinationNumber ?? $this->allowCoordinationNumber;
+        $this->strict = $strict ?? $this->strict;
+    }
+
+    public function validatedBy(): string
     {
         return 'jgi.validator.identity_number';
     }
diff --git a/src/Validator/Constraints/IdentityNumberValidator.php b/src/Validator/Constraints/IdentityNumberValidator.php
index df2d879..23356d1 100644
--- a/src/Validator/Constraints/IdentityNumberValidator.php
+++ b/src/Validator/Constraints/IdentityNumberValidator.php
@@ -7,37 +7,22 @@
 use byrokrat\id\PersonalIdFactory;
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 
 class IdentityNumberValidator extends ConstraintValidator
 {
-    /**
-     * @var PersonalIdFactory
-     */
-    protected $personalIdFactory;
-
-    /**
-     * @var CoordinationIdFactory
-     */
-    protected $coordinationIdFactory;
-
-    /**
-     * @param PersonalIdFactory $personalIdFactory
-     * @param CoordinationIdFactory $coordinationIdFactory
-     */
-    public function __construct(PersonalIdFactory $personalIdFactory, CoordinationIdFactory $coordinationIdFactory)
-    {
-        $this->personalIdFactory = $personalIdFactory;
-        $this->coordinationIdFactory = $coordinationIdFactory;
+    public function __construct(
+        private readonly PersonalIdFactory $personalIdFactory,
+        private readonly CoordinationIdFactory $coordinationIdFactory
+    ) {
     }
 
-    /**
-     * @param mixed $value
-     * @param Constraint|IdentityNumber $constraint
-     *
-     * @return void
-     */
-    public function validate($value, Constraint $constraint)
+    public function validate(mixed $value, Constraint $constraint): void
     {
+        if (!$constraint instanceof IdentityNumber) {
+            throw new UnexpectedTypeException($constraint, IdentityNumber::class);
+        }
+
         if (null === $value || '' === $value) {
             return;
         }
diff --git a/src/Validator/Constraints/OrganizationNumber.php b/src/Validator/Constraints/OrganizationNumber.php
index 6a66499..7fd7d54 100644
--- a/src/Validator/Constraints/OrganizationNumber.php
+++ b/src/Validator/Constraints/OrganizationNumber.php
@@ -4,35 +4,26 @@
 
 use Symfony\Component\Validator\Constraint;
 
-/**
- * @Annotation
- */
+#[\Attribute]
 class OrganizationNumber extends Constraint
 {
-    /**
-     * @var string
-     */
-    public $message = 'This value is not a valid organization number.';
-
-    /**
-     * @var bool
-     */
-    public $strict = false;
-
-    /**
-     * @var bool
-     */
-    public $allowPersonalIdNumber = false;
-
-    /**
-     * @var bool
-     */
-    public $allowCoordinationNumber = false;
-
-    /**
-     * @return string
-     */
-    public function validatedBy()
+    public string $message = 'This value is not a valid organization number.';
+
+    public bool $strict = false;
+
+    public bool $allowPersonalIdNumber = false;
+
+    public bool $allowCoordinationNumber = false;
+
+    public function __construct(?string $message = null, ?bool $strict = null, ?bool $allowPersonalIdNumber = null, ?bool $allowCoordinationNumber = null)
+    {
+        $this->message = $message ?? $this->message;
+        $this->strict = $strict ?? $this->strict;
+        $this->allowPersonalIdNumber = $allowPersonalIdNumber ?? $this->allowPersonalIdNumber;
+        $this->allowCoordinationNumber = $allowCoordinationNumber ?? $this->allowCoordinationNumber;
+    }
+
+    public function validatedBy(): string
     {
         return 'jgi.validator.organization_number';
     }
diff --git a/src/Validator/Constraints/OrganizationNumberValidator.php b/src/Validator/Constraints/OrganizationNumberValidator.php
index e7c5787..17b16f2 100644
--- a/src/Validator/Constraints/OrganizationNumberValidator.php
+++ b/src/Validator/Constraints/OrganizationNumberValidator.php
@@ -8,46 +8,23 @@
 use byrokrat\id\PersonalIdFactory;
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 
 class OrganizationNumberValidator extends ConstraintValidator
 {
-    /**
-     * @var OrganizationIdFactory
-     */
-    protected $organizationIdFactory;
-
-    /**
-     * @var PersonalIdFactory|null
-     */
-    protected $personalIdFactory;
-
-    /**
-     * @var CoordinationIdFactory|null
-     */
-    protected $coordinationIdFactory;
-
-    /**
-     * @param OrganizationIdFactory $factory
-     */
     public function __construct(
-        OrganizationIdFactory $organizationIdFactory,
-        PersonalIdFactory $personalIdFactory = null,
-        CoordinationIdFactory $coordinationIdFactory = null
-    )
-    {
-        $this->organizationIdFactory = $organizationIdFactory;
-        $this->personalIdFactory = $personalIdFactory;
-        $this->coordinationIdFactory = $coordinationIdFactory;
+        private readonly OrganizationIdFactory $organizationIdFactory,
+        private readonly ?PersonalIdFactory $personalIdFactory = null,
+        private readonly ?CoordinationIdFactory $coordinationIdFactory = null
+    ) {
     }
 
-    /**
-     * @param mixed $value
-     * @param Constraint|OrganizationNumber $constraint
-     *
-     * @return void
-     */
-    public function validate($value, Constraint $constraint)
+    public function validate($value, Constraint $constraint): void
     {
+        if (!$constraint instanceof OrganizationNumber) {
+            throw new UnexpectedTypeException($constraint, OrganizationNumber::class);
+        }
+
         if (null === $value || '' === $value) {
             return;
         }
diff --git a/tests/Validator/Constraints/IdentityNumberValidatorTest.php b/tests/Validator/Constraints/IdentityNumberValidatorTest.php
index b1343ea..4c6e124 100644
--- a/tests/Validator/Constraints/IdentityNumberValidatorTest.php
+++ b/tests/Validator/Constraints/IdentityNumberValidatorTest.php
@@ -6,15 +6,14 @@
 use byrokrat\id\PersonalIdFactory;
 use JGI\IdentityNumberValidatorBundle\Validator\Constraints\IdentityNumber;
 use JGI\IdentityNumberValidatorBundle\Validator\Constraints\IdentityNumberValidator;
+use PHPUnit\Framework\Attributes\Test;
+use Symfony\Component\Validator\ConstraintValidatorInterface;
 use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
 use byrokrat\id\Exception;
 
 class IdentityNumberValidatorTest extends ConstraintValidatorTestCase
 {
-    /**
-     * @return IdentityNumberValidator
-     */
-    protected function createValidator()
+    protected function createValidator(): ConstraintValidatorInterface
     {
         return new IdentityNumberValidator(
             $this->createMock(PersonalIdFactory::class),
@@ -22,18 +21,14 @@ protected function createValidator()
         );
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function socialSecurityNumberIsValid()
     {
         $this->validator->validate('-', new IdentityNumber());
         $this->assertNoViolation();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function invalidSocialSecurityNumberIsInvalid()
     {
         $personalIdFactoryMock = $this->createMock(PersonalIdFactory::class);
@@ -52,9 +47,7 @@ public function invalidSocialSecurityNumberIsInvalid()
         ;
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function invalidCoordinationNumberIsInvalid()
     {
         $personalIdFactoryMock = $this->createMock(PersonalIdFactory::class);
@@ -69,25 +62,21 @@ public function invalidCoordinationNumberIsInvalid()
         );
         $this->validator->initialize($this->context);
 
-        $this->validator->validate('-', new IdentityNumber(['allowCoordinationNumber' => true]));
+        $this->validator->validate('-', new IdentityNumber(allowCoordinationNumber: true));
         $this
             ->buildViolation('This value is not a valid identity number or coordination number.')
             ->assertRaised()
         ;
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function coordinationNumberIsValid()
     {
-        $this->validator->validate('-', new IdentityNumber(['allowCoordinationNumber' => true]));
+        $this->validator->validate('-', new IdentityNumber(allowCoordinationNumber: true));
         $this->assertNoViolation();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function coordinationNumberWithoutAllowConfigIsInvalid()
     {
         $personalIdFactoryMock = $this->createMock(PersonalIdFactory::class);
@@ -108,9 +97,7 @@ public function coordinationNumberWithoutAllowConfigIsInvalid()
         ;
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function strictSocialSecurityNumberIsValid()
     {
         $this->validator = new IdentityNumberValidator(
@@ -119,13 +106,11 @@ public function strictSocialSecurityNumberIsValid()
         );
         $this->validator->initialize($this->context);
 
-        $this->validator->validate('195605158616', new IdentityNumber(['strict' => true]));
+        $this->validator->validate('195605158616', new IdentityNumber(strict: true));
         $this->assertNoViolation();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function nonStrictSocialSecurityNumberIsInvalid()
     {
         $this->validator = new IdentityNumberValidator(
@@ -134,7 +119,7 @@ public function nonStrictSocialSecurityNumberIsInvalid()
         );
         $this->validator->initialize($this->context);
 
-        $this->validator->validate('560515-8616', new IdentityNumber(['strict' => true]));
+        $this->validator->validate('560515-8616', new IdentityNumber(strict: true));
         $this
             ->buildViolation('This value is not a valid identity number.')
             ->assertRaised()
diff --git a/tests/Validator/Constraints/OrganizationNumberValidatorTest.php b/tests/Validator/Constraints/OrganizationNumberValidatorTest.php
index af5091b..0366e03 100644
--- a/tests/Validator/Constraints/OrganizationNumberValidatorTest.php
+++ b/tests/Validator/Constraints/OrganizationNumberValidatorTest.php
@@ -5,31 +5,26 @@
 use byrokrat\id\OrganizationIdFactory;
 use JGI\IdentityNumberValidatorBundle\Validator\Constraints\OrganizationNumber;
 use JGI\IdentityNumberValidatorBundle\Validator\Constraints\OrganizationNumberValidator;
+use PHPUnit\Framework\Attributes\Test;
+use Symfony\Component\Validator\ConstraintValidatorInterface;
 use Symfony\Component\Validator\Test\ConstraintValidatorTestCase;
 use byrokrat\id\Exception;
 
 class OrganizationNumberValidatorTest extends ConstraintValidatorTestCase
 {
-    /**
-     * @return OrganizationNumberValidator
-     */
-    protected function createValidator()
+    protected function createValidator(): ConstraintValidatorInterface
     {
         return new OrganizationNumberValidator($this->createMock(OrganizationIdFactory::class));
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function organizationNumberIsValid()
     {
         $this->validator->validate('-', new OrganizationNumber());
         $this->assertNoViolation();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function invalidOrganizationNumberIsInvalid()
     {
         $organizationIdFactoryMock = $this->createMock(OrganizationIdFactory::class);
@@ -45,27 +40,23 @@ public function invalidOrganizationNumberIsInvalid()
         ;
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function strictOrganizationNumberIsValid()
     {
         $this->validator = new OrganizationNumberValidator($this->createMock(OrganizationIdFactory::class));
         $this->validator->initialize($this->context);
 
-        $this->validator->validate('5569209900', new OrganizationNumber(['strict' => true]));
+        $this->validator->validate('5569209900', new OrganizationNumber(strict: true));
         $this->assertNoViolation();
     }
 
-    /**
-     * @test
-     */
+    #[Test]
     public function nonStrictOrganizationNumberIsInvalid()
     {
         $this->validator = new OrganizationNumberValidator($this->createMock(OrganizationIdFactory::class));
         $this->validator->initialize($this->context);
 
-        $this->validator->validate('556920-9900', new OrganizationNumber(['strict' => true]));
+        $this->validator->validate('556920-9900', new OrganizationNumber(strict: true));
         $this
             ->buildViolation('This value is not a valid organization number.')
             ->assertRaised()