diff --git a/.php-cs-fixer.php b/.php-cs-fixer.php
index 9c1c04b..c12ff17 100644
--- a/.php-cs-fixer.php
+++ b/.php-cs-fixer.php
@@ -19,7 +19,7 @@ EOF;
 
 $config = new PhpCsFixer\Config();
 return $config->setRules([
-    '@PHP80Migration' => true,
+    '@PHP80Migration:risky' => true,
     '@PSR12' => true,
     'header_comment' => [
         'comment_type' => 'PHPDoc',
diff --git a/composer.json b/composer.json
index ddb662f..ab767ec 100644
--- a/composer.json
+++ b/composer.json
@@ -42,7 +42,7 @@
   "scripts": {
     "test": "./vendor/bin/phpunit --no-coverage",
     "check-style": "./vendor/bin/php-cs-fixer fix --verbose --dry-run",
-    "fix-style": "./vendor/bin/php-cs-fixer fix --verbose",
+    "fix-style": "./vendor/bin/php-cs-fixer fix --verbose --allow-risky=yes",
     "check-code": "./vendor/bin/phpstan analyse -c phpstan.neon --no-progress --ansi"
   }
 }
diff --git a/src/Entities/Account.php b/src/Entities/Account.php
index 1c81e6e..57f142b 100644
--- a/src/Entities/Account.php
+++ b/src/Entities/Account.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use D3\KlicktippPhpClient\Exceptions\BaseException;
diff --git a/src/Entities/Field.php b/src/Entities/Field.php
index 199c84f..a28999c 100644
--- a/src/Entities/Field.php
+++ b/src/Entities/Field.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use D3\KlicktippPhpClient\Exceptions\BaseException;
diff --git a/src/Entities/FieldList.php b/src/Entities/FieldList.php
index 8b98bea..dbe9d3e 100644
--- a/src/Entities/FieldList.php
+++ b/src/Entities/FieldList.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use Doctrine\Common\Collections\ArrayCollection;
diff --git a/src/Entities/Subscriber.php b/src/Entities/Subscriber.php
index 787eee4..8cc322d 100644
--- a/src/Entities/Subscriber.php
+++ b/src/Entities/Subscriber.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use D3\KlicktippPhpClient\Exceptions\BaseException;
@@ -158,9 +160,7 @@ class Subscriber extends ArrayCollection
     public function getFields(): ArrayCollection
     {
         return $this->filter(
-            function ($value, $key) {
-                return str_starts_with($key, 'field');
-            }
+            fn ($value, $key) => str_starts_with($key, 'field')
         );
     }
 
diff --git a/src/Entities/SubscriberList.php b/src/Entities/SubscriberList.php
index bbc48a5..16ce28e 100644
--- a/src/Entities/SubscriberList.php
+++ b/src/Entities/SubscriberList.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use Doctrine\Common\Collections\ArrayCollection;
diff --git a/src/Entities/Subscription.php b/src/Entities/Subscription.php
index 7c75649..41d242c 100644
--- a/src/Entities/Subscription.php
+++ b/src/Entities/Subscription.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use D3\KlicktippPhpClient\Exceptions\BaseException;
diff --git a/src/Entities/SubscriptionList.php b/src/Entities/SubscriptionList.php
index 87bffe0..466e188 100644
--- a/src/Entities/SubscriptionList.php
+++ b/src/Entities/SubscriptionList.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use Doctrine\Common\Collections\ArrayCollection;
diff --git a/src/Entities/Tag.php b/src/Entities/Tag.php
index 7b2c651..85716fe 100644
--- a/src/Entities/Tag.php
+++ b/src/Entities/Tag.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use D3\KlicktippPhpClient\Exceptions\BaseException;
diff --git a/src/Entities/TagList.php b/src/Entities/TagList.php
index cd76038..e98069b 100644
--- a/src/Entities/TagList.php
+++ b/src/Entities/TagList.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Entities;
 
 use Doctrine\Common\Collections\ArrayCollection;
diff --git a/src/Exceptions/BaseException.php b/src/Exceptions/BaseException.php
index 94a3578..5af096d 100644
--- a/src/Exceptions/BaseException.php
+++ b/src/Exceptions/BaseException.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Exceptions;
 
 use Exception;
diff --git a/src/Exceptions/NoCredentialsException.php b/src/Exceptions/NoCredentialsException.php
index 2964ce4..59c5a09 100644
--- a/src/Exceptions/NoCredentialsException.php
+++ b/src/Exceptions/NoCredentialsException.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Exceptions;
 
 class NoCredentialsException extends BaseException
diff --git a/src/Resources/Account.php b/src/Resources/Account.php
index 0e48d6c..fa3524e 100644
--- a/src/Resources/Account.php
+++ b/src/Resources/Account.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Entities\Account as AccountEntity;
diff --git a/src/Resources/Field.php b/src/Resources/Field.php
index 5e3ee81..86a4dfa 100644
--- a/src/Resources/Field.php
+++ b/src/Resources/Field.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Entities\Field as FieldEntity;
@@ -63,7 +65,7 @@ class Field extends Model
      */
     public function create(string $name): string
     {
-        return current(
+        return (string) current(
             $this->connection->requestAndParse(
                 'POST',
                 'field.json',
diff --git a/src/Resources/Model.php b/src/Resources/Model.php
index d8e3e29..3c354a1 100644
--- a/src/Resources/Model.php
+++ b/src/Resources/Model.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Connection;
diff --git a/src/Resources/Subscriber.php b/src/Resources/Subscriber.php
index db8046d..41237f4 100644
--- a/src/Resources/Subscriber.php
+++ b/src/Resources/Subscriber.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Entities\Subscriber as SubscriberEntity;
@@ -111,7 +113,7 @@ class Subscriber extends Model
      */
     public function search(string $mailAddress): string
     {
-        return current(
+        return (string) current(
             $this->connection->requestAndParse(
                 'POST',
                 'subscriber/search.json',
@@ -328,9 +330,9 @@ class Subscriber extends Model
     /**
      * @throws BaseException
      */
-    public function signoff(string $apikey, string $emailAddress): string
+    public function signoff(string $apikey, string $emailAddress): bool
     {
-        return current(
+        return (bool) current(
             $this->connection->requestAndParse(
                 'POST',
                 'subscriber/signoff.json',
diff --git a/src/Resources/SubscriptionProcess.php b/src/Resources/SubscriptionProcess.php
index 2baa5dc..d31e223 100644
--- a/src/Resources/SubscriptionProcess.php
+++ b/src/Resources/SubscriptionProcess.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Entities\Subscription as SubscriptionEntity;
diff --git a/src/Resources/Tag.php b/src/Resources/Tag.php
index fcae57c..7ae2c89 100644
--- a/src/Resources/Tag.php
+++ b/src/Resources/Tag.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\Resources;
 
 use D3\KlicktippPhpClient\Entities\Tag as TagEntity;
@@ -64,7 +66,7 @@ class Tag extends Model
      */
     public function create(string $name): string
     {
-        return current(
+        return (string) current(
             $this->connection->requestAndParse(
                 'POST',
                 'tag.json',
diff --git a/tests/integration/IntegrationTestCase.php b/tests/integration/IntegrationTestCase.php
index 2f76040..250abfe 100644
--- a/tests/integration/IntegrationTestCase.php
+++ b/tests/integration/IntegrationTestCase.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration;
 
 use D3\KlicktippPhpClient\Connection;
diff --git a/tests/integration/Resources/AccountTest.php b/tests/integration/Resources/AccountTest.php
index 582b139..15f91e9 100644
--- a/tests/integration/Resources/AccountTest.php
+++ b/tests/integration/Resources/AccountTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration\Resources;
 
 use D3\KlicktippPhpClient\Entities\Account as AccountEntity;
@@ -139,7 +141,7 @@ class AccountTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Account::getEntity
      * @dataProvider getDataProvider
      */
-    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new Account($this->getConnectionMock($response));
 
@@ -180,7 +182,7 @@ class AccountTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Account::update
      * @dataProvider updateDataProvider
      */
-    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new Account($this->getConnectionMock($response));
 
diff --git a/tests/integration/Resources/FieldTest.php b/tests/integration/Resources/FieldTest.php
index 12bee6d..dd8d7f2 100644
--- a/tests/integration/Resources/FieldTest.php
+++ b/tests/integration/Resources/FieldTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration\Resources;
 
 use D3\KlicktippPhpClient\Entities\Field as FieldEntity;
@@ -37,7 +39,7 @@ class FieldTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Field::index
      * @dataProvider indexDataProvider
      */
-    public function testIndex(ResponseInterface $response, ?FieldList $expected, bool $expectException = false)
+    public function testIndex(ResponseInterface $response, ?FieldList $expected, bool $expectException = false): void
     {
         $sut = new Field($this->getConnectionMock($response));
 
@@ -102,7 +104,7 @@ class FieldTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Field::getEntity
      * @dataProvider getDataProvider
      */
-    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new Field($this->getConnectionMock($response));
 
@@ -139,7 +141,7 @@ class FieldTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Field::create
      * @dataProvider createDataProvider
      */
-    public function testCreate(ResponseInterface $response, ?string $expected, bool $expectException = false)
+    public function testCreate(ResponseInterface $response, ?string $expected, bool $expectException = false): void
     {
         $sut = new Field($this->getConnectionMock($response));
 
@@ -170,7 +172,7 @@ class FieldTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Field::update
      * @dataProvider updateDataProvider
      */
-    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new Field($this->getConnectionMock($response));
 
@@ -201,7 +203,7 @@ class FieldTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Field::delete
      * @dataProvider deleteDataProvider
      */
-    public function testDelete(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testDelete(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new Field($this->getConnectionMock($response));
 
diff --git a/tests/integration/Resources/SubscriberTest.php b/tests/integration/Resources/SubscriberTest.php
index 80d42e8..4a80e27 100644
--- a/tests/integration/Resources/SubscriberTest.php
+++ b/tests/integration/Resources/SubscriberTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration\Resources;
 
 use D3\KlicktippPhpClient\Entities\Subscriber as SubscriberEntity;
@@ -54,7 +56,7 @@ class SubscriberTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Subscriber::index
      * @dataProvider indexDataProvider
      */
-    public function testIndex(ResponseInterface $response, ?SubscriberList $expected, bool $expectException = false)
+    public function testIndex(ResponseInterface $response, ?SubscriberList $expected, bool $expectException = false): void
     {
         $sut = new Subscriber($this->getConnectionMock($response));
 
@@ -96,7 +98,7 @@ class SubscriberTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Subscriber::getEntity
      * @dataProvider getDataProvider
      */
-    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new Subscriber($this->getConnectionMock($response));
 
diff --git a/tests/integration/Resources/SubscriptionProcessTest.php b/tests/integration/Resources/SubscriptionProcessTest.php
index 3eb56da..003a98e 100644
--- a/tests/integration/Resources/SubscriptionProcessTest.php
+++ b/tests/integration/Resources/SubscriptionProcessTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration\Resources;
 
 use D3\KlicktippPhpClient\Entities\Subscription;
@@ -36,7 +38,7 @@ class SubscriptionProcessTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\SubscriptionProcess::index
      * @dataProvider indexDataProvider
      */
-    public function testIndex(ResponseInterface $response, ?SubscriptionList $expected, bool $expectException = false)
+    public function testIndex(ResponseInterface $response, ?SubscriptionList $expected, bool $expectException = false): void
     {
         $sut = new SubscriptionProcess($this->getConnectionMock($response));
 
@@ -73,7 +75,7 @@ class SubscriptionProcessTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\SubscriptionProcess::getEntity
      * @dataProvider getDataProvider
      */
-    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new SubscriptionProcess($this->getConnectionMock($response));
 
@@ -121,7 +123,7 @@ class SubscriptionProcessTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\SubscriptionProcess::create
      * @dataProvider getDataProvider
      */
-    public function testCreate(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testCreate(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new SubscriptionProcess($this->getConnectionMock($response));
 
@@ -145,7 +147,7 @@ class SubscriptionProcessTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\SubscriptionProcess::update
      * @dataProvider updateDataProvider
      */
-    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new SubscriptionProcess($this->getConnectionMock($response));
 
@@ -176,7 +178,7 @@ class SubscriptionProcessTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\SubscriptionProcess::redirect
      * @dataProvider redirectDataProvider
      */
-    public function testRedirect(ResponseInterface $response, ?string $expected, bool $expectException = false)
+    public function testRedirect(ResponseInterface $response, ?string $expected, bool $expectException = false): void
     {
         $sut = new SubscriptionProcess($this->getConnectionMock($response));
 
diff --git a/tests/integration/Resources/TagTest.php b/tests/integration/Resources/TagTest.php
index 505e1e9..7c6d82a 100644
--- a/tests/integration/Resources/TagTest.php
+++ b/tests/integration/Resources/TagTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\integration\Resources;
 
 use D3\KlicktippPhpClient\Entities\Tag as TagEntity;
@@ -36,7 +38,7 @@ class TagTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Tag::index
      * @dataProvider indexDataProvider
      */
-    public function testIndex(ResponseInterface $response, ?TagList $expected, bool $expectException = false)
+    public function testIndex(ResponseInterface $response, ?TagList $expected, bool $expectException = false): void
     {
         $sut = new Tag($this->getConnectionMock($response));
 
@@ -73,7 +75,7 @@ class TagTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Tag::getEntity
      * @dataProvider getDataProvider
      */
-    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false)
+    public function testGet(ResponseInterface $response, ?array $expected, bool $expectException = false): void
     {
         $sut = new Tag($this->getConnectionMock($response));
 
@@ -112,7 +114,7 @@ class TagTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Tag::create
      * @dataProvider createDataProvider
      */
-    public function testCreate(ResponseInterface $response, ?string $expected, bool $expectException = false)
+    public function testCreate(ResponseInterface $response, ?string $expected, bool $expectException = false): void
     {
         $sut = new Tag($this->getConnectionMock($response));
 
@@ -143,7 +145,7 @@ class TagTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Tag::update
      * @dataProvider updateDataProvider
      */
-    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testUpdate(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new Tag($this->getConnectionMock($response));
 
@@ -174,7 +176,7 @@ class TagTest extends IntegrationTestCase
      * @covers \D3\KlicktippPhpClient\Resources\Tag::delete
      * @dataProvider deleteDataProvider
      */
-    public function testDelete(ResponseInterface $response, ?bool $expected, bool $expectException = false)
+    public function testDelete(ResponseInterface $response, ?bool $expected, bool $expectException = false): void
     {
         $sut = new Tag($this->getConnectionMock($response));
 
diff --git a/tests/unit/Entities/AccountTest.php b/tests/unit/Entities/AccountTest.php
index 9321e7a..f6f5d8f 100644
--- a/tests/unit/Entities/AccountTest.php
+++ b/tests/unit/Entities/AccountTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\unit\Entities;
 
 use D3\KlicktippPhpClient\Entities\Account;
diff --git a/tests/unit/Entities/FieldTest.php b/tests/unit/Entities/FieldTest.php
index f79bb3a..d74aec0 100644
--- a/tests/unit/Entities/FieldTest.php
+++ b/tests/unit/Entities/FieldTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\unit\Entities;
 
 use D3\KlicktippPhpClient\Entities\Field;
@@ -73,7 +75,7 @@ class FieldTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Field::getName
      * @dataProvider getSomethingDataProvider
      */
-    public function testGetSomething(string $methodName, string $expectedValue)
+    public function testGetSomething(string $methodName, string $expectedValue): void
     {
         $this->assertSame(
             $expectedValue,
diff --git a/tests/unit/Entities/SubscriberTest.php b/tests/unit/Entities/SubscriberTest.php
index 93bce20..d719d7a 100644
--- a/tests/unit/Entities/SubscriberTest.php
+++ b/tests/unit/Entities/SubscriberTest.php
@@ -13,6 +13,8 @@
  * @link      https://www.oxidmodule.com
  */
 
+declare(strict_types=1);
+
 namespace D3\KlicktippPhpClient\tests\unit\Entities;
 
 use D3\KlicktippPhpClient\Entities\Subscriber;
@@ -169,7 +171,7 @@ class SubscriberTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::getSmsReferrer
      * @dataProvider getSomethingDataProvider
      */
-    public function testGetSomething(string $methodName, string $expectedValue)
+    public function testGetSomething(string $methodName, string $expectedValue): void
     {
         $this->assertSame(
             $expectedValue,
@@ -371,7 +373,7 @@ class SubscriberTest extends TestCase
      * @throws ReflectionException
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::getFields
      */
-    public function testGetFields()
+    public function testGetFields(): void
     {
         $fields = $this->callMethod(
             $this->entity,
@@ -466,7 +468,7 @@ class SubscriberTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::getOutbounds
      * @dataProvider getTagsDataProvider
      */
-    public function testGetTags(string $methodName, int $expectedCount)
+    public function testGetTags(string $methodName, int $expectedCount): void
     {
         $tags = $this->callMethod(
             $this->entity,
@@ -497,7 +499,7 @@ class SubscriberTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::isTagSet
      * @dataProvider isTagSetDataProvider
      */
-    public function testIsTagSet(string $searchTagId, bool $expected)
+    public function testIsTagSet(string $searchTagId, bool $expected): void
     {
         $tagList = new ArrayCollection([
             "12494453",
@@ -628,7 +630,7 @@ class SubscriberTest extends TestCase
         ?array $newTagList,
         InvokedCount $removeTagInvocation,
         InvokedCount $setTagInvocation
-    ) {
+    ): void {
         $entityMock = $this->getMockBuilder(Subscriber::class)
             ->disableOriginalConstructor()
             ->onlyMethods(['getTags'])
@@ -671,7 +673,7 @@ class SubscriberTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::isManualTagSet
      * @dataProvider isManualTagSetDataProvider
      */
-    public function testIsManualTagSet(string $searchTagId, bool $expected)
+    public function testIsManualTagSet(string $searchTagId, bool $expected): void
     {
         $this->assertSame(
             $expected,
@@ -698,7 +700,7 @@ class SubscriberTest extends TestCase
      * @covers \D3\KlicktippPhpClient\Entities\Subscriber::getFinishedCampaignTime
      * @dataProvider getTagDataProvider
      */
-    public function testGetTag(string $testMethodName, string $invokedMethodName)
+    public function testGetTag(string $testMethodName, string $invokedMethodName): void
     {
         $fixtureDate = '2024-12-24 18:00:00';
         $fixture = new DateTime($fixtureDate);