diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index 1185b9c..2446c56 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use CodeIgniter\CodingStandard\CodeIgniter4;
 use Nexus\CsConfig\Factory;
 use PhpCsFixer\Finder;
@@ -13,7 +15,10 @@
     ->exclude('build')
     ->append([__FILE__]);
 
-$overrides = [];
+$overrides = [
+    'declare_strict_types' => true,
+    'void_return'          => true,
+];
 
 $options = [
     'finder'    => $finder,
diff --git a/src/BaseJob.php b/src/BaseJob.php
index ad67410..2a632ea 100644
--- a/src/BaseJob.php
+++ b/src/BaseJob.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue;
 
 abstract class BaseJob
diff --git a/src/Commands/Generators/JobGenerator.php b/src/Commands/Generators/JobGenerator.php
index 2996335..5e525d4 100644
--- a/src/Commands/Generators/JobGenerator.php
+++ b/src/Commands/Generators/JobGenerator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands\Generators;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueClear.php b/src/Commands/QueueClear.php
index 0080454..cb86539 100644
--- a/src/Commands/QueueClear.php
+++ b/src/Commands/QueueClear.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueFailed.php b/src/Commands/QueueFailed.php
index 3968095..5a0b791 100644
--- a/src/Commands/QueueFailed.php
+++ b/src/Commands/QueueFailed.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueFlush.php b/src/Commands/QueueFlush.php
index f1868b1..47e85c8 100644
--- a/src/Commands/QueueFlush.php
+++ b/src/Commands/QueueFlush.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueForget.php b/src/Commands/QueueForget.php
index df55a5d..f5ebdab 100644
--- a/src/Commands/QueueForget.php
+++ b/src/Commands/QueueForget.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueuePublish.php b/src/Commands/QueuePublish.php
index e0d1d8c..4caddc5 100644
--- a/src/Commands/QueuePublish.php
+++ b/src/Commands/QueuePublish.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
@@ -13,10 +15,7 @@ class QueuePublish extends BaseCommand
     protected $name        = 'queue:publish';
     protected $description = 'Publish QueueJob config file into the current application.';
 
-    /**
-     * @return void
-     */
-    public function run(array $params)
+    public function run(array $params): void
     {
         $source = service('autoloader')->getNamespace('CodeIgniter\\Queue')[0];
 
diff --git a/src/Commands/QueueRetry.php b/src/Commands/QueueRetry.php
index ad993b5..88eed8d 100644
--- a/src/Commands/QueueRetry.php
+++ b/src/Commands/QueueRetry.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueStop.php b/src/Commands/QueueStop.php
index 0becf7a..d9a7e87 100644
--- a/src/Commands/QueueStop.php
+++ b/src/Commands/QueueStop.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Commands/QueueWork.php b/src/Commands/QueueWork.php
index 18235c3..ec46eae 100644
--- a/src/Commands/QueueWork.php
+++ b/src/Commands/QueueWork.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Commands;
 
 use CodeIgniter\CLI\BaseCommand;
diff --git a/src/Config/Queue.php b/src/Config/Queue.php
index db407e0..ab9e2e5 100644
--- a/src/Config/Queue.php
+++ b/src/Config/Queue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Config;
 
 use CodeIgniter\Config\BaseConfig;
diff --git a/src/Config/Registrar.php b/src/Config/Registrar.php
index 3f40e64..0924f94 100644
--- a/src/Config/Registrar.php
+++ b/src/Config/Registrar.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Config;
 
 class Registrar
diff --git a/src/Config/Services.php b/src/Config/Services.php
index 353e8ff..948e042 100644
--- a/src/Config/Services.php
+++ b/src/Config/Services.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Config;
 
 use CodeIgniter\Config\BaseService;
diff --git a/src/Database/Migrations/2023-10-12-112040_AddQueueTables.php b/src/Database/Migrations/2023-10-12-112040_AddQueueTables.php
index 3e80440..3c1bf93 100644
--- a/src/Database/Migrations/2023-10-12-112040_AddQueueTables.php
+++ b/src/Database/Migrations/2023-10-12-112040_AddQueueTables.php
@@ -1,12 +1,14 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Database\Migrations;
 
 use CodeIgniter\Database\Migration;
 
 class AddQueueTables extends Migration
 {
-    public function up()
+    public function up(): void
     {
         $this->forge->addField([
             'id'           => ['type' => 'bigint', 'constraint' => 11, 'unsigned' => true, 'auto_increment' => true],
@@ -34,7 +36,7 @@ public function up()
         $this->forge->createTable('queue_jobs_failed', true);
     }
 
-    public function down()
+    public function down(): void
     {
         $this->forge->dropTable('queue_jobs', true);
         $this->forge->dropTable('queue_jobs_failed', true);
diff --git a/src/Database/Migrations/2023-11-05-064053_AddPriorityField.php b/src/Database/Migrations/2023-11-05-064053_AddPriorityField.php
index f437963..a4cf410 100644
--- a/src/Database/Migrations/2023-11-05-064053_AddPriorityField.php
+++ b/src/Database/Migrations/2023-11-05-064053_AddPriorityField.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Database\Migrations;
 
 use CodeIgniter\Database\BaseConnection;
@@ -10,7 +12,7 @@
  */
 class AddPriorityField extends Migration
 {
-    public function up()
+    public function up(): void
     {
         $fields = [
             'priority' => [
@@ -40,7 +42,7 @@ public function up()
         $this->forge->processIndexes('queue_jobs');
     }
 
-    public function down()
+    public function down(): void
     {
         // Ugly fix for dropping the correct index
         $keys = $this->db->getIndexData('queue_jobs');
diff --git a/src/Entities/QueueJob.php b/src/Entities/QueueJob.php
index 28fac48..b4c6523 100644
--- a/src/Entities/QueueJob.php
+++ b/src/Entities/QueueJob.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Entities;
 
 use CodeIgniter\Entity\Entity;
diff --git a/src/Entities/QueueJobFailed.php b/src/Entities/QueueJobFailed.php
index 745a6c8..8d3e7c6 100644
--- a/src/Entities/QueueJobFailed.php
+++ b/src/Entities/QueueJobFailed.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Entities;
 
 use CodeIgniter\Entity\Entity;
diff --git a/src/Enums/Status.php b/src/Enums/Status.php
index d1c4853..ddc05f9 100644
--- a/src/Enums/Status.php
+++ b/src/Enums/Status.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Enums;
 
 enum Status: int
diff --git a/src/Exceptions/QueueException.php b/src/Exceptions/QueueException.php
index ca208da..d7db38a 100644
--- a/src/Exceptions/QueueException.php
+++ b/src/Exceptions/QueueException.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Exceptions;
 
 use RuntimeException;
diff --git a/src/Handlers/BaseHandler.php b/src/Handlers/BaseHandler.php
index 16da9bc..82d55c8 100644
--- a/src/Handlers/BaseHandler.php
+++ b/src/Handlers/BaseHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Handlers;
 
 use CodeIgniter\I18n\Time;
diff --git a/src/Handlers/DatabaseHandler.php b/src/Handlers/DatabaseHandler.php
index e70ae43..8afe7c5 100644
--- a/src/Handlers/DatabaseHandler.php
+++ b/src/Handlers/DatabaseHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Handlers;
 
 use CodeIgniter\I18n\Time;
diff --git a/src/Handlers/PredisHandler.php b/src/Handlers/PredisHandler.php
index ea2267c..c5a33af 100644
--- a/src/Handlers/PredisHandler.php
+++ b/src/Handlers/PredisHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Handlers;
 
 use CodeIgniter\Exceptions\CriticalError;
diff --git a/src/Handlers/RedisHandler.php b/src/Handlers/RedisHandler.php
index 64f5562..d435523 100644
--- a/src/Handlers/RedisHandler.php
+++ b/src/Handlers/RedisHandler.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Handlers;
 
 use CodeIgniter\Exceptions\CriticalError;
diff --git a/src/Interfaces/JobInterface.php b/src/Interfaces/JobInterface.php
index eb466a6..cde2842 100644
--- a/src/Interfaces/JobInterface.php
+++ b/src/Interfaces/JobInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Interfaces;
 
 interface JobInterface
diff --git a/src/Interfaces/QueueInterface.php b/src/Interfaces/QueueInterface.php
index 5a45c20..bddbd15 100644
--- a/src/Interfaces/QueueInterface.php
+++ b/src/Interfaces/QueueInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Interfaces;
 
 use CodeIgniter\Queue\Entities\QueueJob;
diff --git a/src/Language/en/Queue.php b/src/Language/en/Queue.php
index c4bab3c..e864b84 100644
--- a/src/Language/en/Queue.php
+++ b/src/Language/en/Queue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return [
     'generator' => [
         'className' => [
diff --git a/src/Models/QueueJobFailedModel.php b/src/Models/QueueJobFailedModel.php
index 2087946..92270f6 100644
--- a/src/Models/QueueJobFailedModel.php
+++ b/src/Models/QueueJobFailedModel.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue\Models;
 
 use CodeIgniter\Model;
diff --git a/src/Payload.php b/src/Payload.php
index e641ed9..72e18ed 100644
--- a/src/Payload.php
+++ b/src/Payload.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue;
 
 use JsonSerializable;
diff --git a/src/Queue.php b/src/Queue.php
index b491406..5dbbe1c 100644
--- a/src/Queue.php
+++ b/src/Queue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace CodeIgniter\Queue;
 
 use CodeIgniter\Queue\Config\Queue as QueueConfig;
diff --git a/tests/DatabaseHandlerTest.php b/tests/DatabaseHandlerTest.php
index af059e6..62eff81 100644
--- a/tests/DatabaseHandlerTest.php
+++ b/tests/DatabaseHandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\Queue\Entities\QueueJob;
@@ -31,13 +33,13 @@ protected function setUp(): void
         $this->config = config(QueueConfig::class);
     }
 
-    public function testDatabaseHandler()
+    public function testDatabaseHandler(): void
     {
         $handler = new DatabaseHandler($this->config);
         $this->assertInstanceOf(DatabaseHandler::class, $handler);
     }
 
-    public function testPriority()
+    public function testPriority(): void
     {
         $handler = new DatabaseHandler($this->config);
         $handler->setPriority('high');
@@ -45,7 +47,7 @@ public function testPriority()
         $this->assertSame('high', self::getPrivateProperty($handler, 'priority'));
     }
 
-    public function testPriorityNameException()
+    public function testPriorityNameException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The priority name should consists only lowercase letters.');
@@ -54,7 +56,7 @@ public function testPriorityNameException()
         $handler->setPriority('high_:');
     }
 
-    public function testPriorityNameLengthException()
+    public function testPriorityNameLengthException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The priority name is too long. It should be no longer than 64 letters.');
@@ -66,7 +68,7 @@ public function testPriorityNameLengthException()
     /**
      * @throws ReflectionException
      */
-    public function testPush()
+    public function testPush(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->push('queue', 'success', ['key' => 'value']);
@@ -81,7 +83,7 @@ public function testPush()
     /**
      * @throws ReflectionException
      */
-    public function testPushWithPriority()
+    public function testPushWithPriority(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->setPriority('high')->push('queue', 'success', ['key' => 'value']);
@@ -94,7 +96,7 @@ public function testPushWithPriority()
         ]);
     }
 
-    public function testPushAndPopWithPriority()
+    public function testPushAndPopWithPriority(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->push('queue', 'success', ['key1' => 'value1']);
@@ -129,7 +131,7 @@ public function testPushAndPopWithPriority()
     /**
      * @throws ReflectionException
      */
-    public function testPushException()
+    public function testPushException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This job name is not defined in the $jobHandlers array.');
@@ -141,7 +143,7 @@ public function testPushException()
     /**
      * @throws ReflectionException
      */
-    public function testPushWithPriorityException()
+    public function testPushWithPriorityException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This queue has incorrectly defined priority: "invalid" for the queue: "queue".');
@@ -153,7 +155,7 @@ public function testPushWithPriorityException()
     /**
      * @throws ReflectionException
      */
-    public function testPushWithIncorrectQueueFormatException()
+    public function testPushWithIncorrectQueueFormatException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The queue name should consists only lowercase letters or numbers.');
@@ -165,7 +167,7 @@ public function testPushWithIncorrectQueueFormatException()
     /**
      * @throws ReflectionException
      */
-    public function testPushWithTooLongQueueNameException()
+    public function testPushWithTooLongQueueNameException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The queue name is too long. It should be no longer than 64 letters.');
@@ -177,7 +179,7 @@ public function testPushWithTooLongQueueNameException()
     /**
      * @throws ReflectionException
      */
-    public function testPop()
+    public function testPop(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->pop('queue1', ['default']);
@@ -192,7 +194,7 @@ public function testPop()
     /**
      * @throws ReflectionException
      */
-    public function testPopEmpty()
+    public function testPopEmpty(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->pop('queue123', ['default']);
@@ -203,7 +205,7 @@ public function testPopEmpty()
     /**
      * @throws ReflectionException
      */
-    public function testLater()
+    public function testLater(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -225,7 +227,7 @@ public function testLater()
     /**
      * @throws ReflectionException
      */
-    public function testFailedAndKeepJob()
+    public function testFailedAndKeepJob(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -244,7 +246,7 @@ public function testFailedAndKeepJob()
         ]);
     }
 
-    public function testFailedAndDontKeepJob()
+    public function testFailedAndDontKeepJob(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -266,7 +268,7 @@ public function testFailedAndDontKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testDoneAndKeepJob()
+    public function testDoneAndKeepJob(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -283,7 +285,7 @@ public function testDoneAndKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testDoneAndDontKeepJob()
+    public function testDoneAndDontKeepJob(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -296,7 +298,7 @@ public function testDoneAndDontKeepJob()
         ]);
     }
 
-    public function testClear()
+    public function testClear(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->clear('queue1');
@@ -311,7 +313,7 @@ public function testClear()
         ]);
     }
 
-    public function testRetry()
+    public function testRetry(): void
     {
         $handler = new DatabaseHandler($this->config);
         $count   = $handler->retry(1, 'queue1');
@@ -328,7 +330,7 @@ public function testRetry()
         ]);
     }
 
-    public function testForget()
+    public function testForget(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->forget(1);
@@ -340,7 +342,7 @@ public function testForget()
         ]);
     }
 
-    public function testForgetFalse()
+    public function testForgetFalse(): void
     {
         $handler = new DatabaseHandler($this->config);
         $result  = $handler->forget(1111);
@@ -351,7 +353,7 @@ public function testForgetFalse()
     /**
      * @throws ReflectionException
      */
-    public function testFlush()
+    public function testFlush(): void
     {
         $handler  = new DatabaseHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -373,7 +375,7 @@ public function testFlush()
         ]);
     }
 
-    public function testFlushAll()
+    public function testFlushAll(): void
     {
         $handler = new DatabaseHandler($this->config);
         $handler->flush(null, null);
@@ -382,7 +384,7 @@ public function testFlushAll()
         ]);
     }
 
-    public function testListFailed()
+    public function testListFailed(): void
     {
         $handler = new DatabaseHandler($this->config);
         $list    = $handler->listFailed('queue1');
diff --git a/tests/PredisHandlerTest.php b/tests/PredisHandlerTest.php
index 6cccdfe..ba7a40c 100644
--- a/tests/PredisHandlerTest.php
+++ b/tests/PredisHandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace ThirdParty\queue\tests;
 
 use CodeIgniter\I18n\Time;
@@ -30,13 +32,13 @@ protected function setUp(): void
         $this->config = config(QueueConfig::class);
     }
 
-    public function testPredisHandler()
+    public function testPredisHandler(): void
     {
         $handler = new PredisHandler($this->config);
         $this->assertInstanceOf(PredisHandler::class, $handler);
     }
 
-    public function testPriority()
+    public function testPriority(): void
     {
         $handler = new PredisHandler($this->config);
         $handler->setPriority('high');
@@ -44,7 +46,7 @@ public function testPriority()
         $this->assertSame('high', self::getPrivateProperty($handler, 'priority'));
     }
 
-    public function testPriorityException()
+    public function testPriorityException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The priority name should consists only lowercase letters.');
@@ -56,7 +58,7 @@ public function testPriorityException()
     /**
      * @throws ReflectionException
      */
-    public function testPush()
+    public function testPush(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->push('queue', 'success', ['key' => 'value']);
@@ -75,7 +77,7 @@ public function testPush()
     /**
      * @throws ReflectionException
      */
-    public function testPushWithPriority()
+    public function testPushWithPriority(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->setPriority('high')->push('queue', 'success', ['key' => 'value']);
@@ -91,7 +93,7 @@ public function testPushWithPriority()
         $this->assertSame(['key' => 'value'], $queueJob->payload['data']);
     }
 
-    public function testPushException()
+    public function testPushException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This job name is not defined in the $jobHandlers array.');
@@ -100,7 +102,7 @@ public function testPushException()
         $handler->push('queue', 'not-exists', ['key' => 'value']);
     }
 
-    public function testPushWithPriorityException()
+    public function testPushWithPriorityException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This queue has incorrectly defined priority: "invalid" for the queue: "queue".');
@@ -112,7 +114,7 @@ public function testPushWithPriorityException()
     /**
      * @throws ReflectionException
      */
-    public function testPop()
+    public function testPop(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->pop('queue1', ['default']);
@@ -125,7 +127,7 @@ public function testPop()
         $this->assertSame(1, $predis->hexists('queues:queue1::reserved', $result->id));
     }
 
-    public function testPopEmpty()
+    public function testPopEmpty(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->pop('queue123', ['default']);
@@ -136,7 +138,7 @@ public function testPopEmpty()
     /**
      * @throws ReflectionException
      */
-    public function testLater()
+    public function testLater(): void
     {
         $handler  = new PredisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -155,7 +157,7 @@ public function testLater()
     /**
      * @throws ReflectionException
      */
-    public function testFailedAndKeepJob()
+    public function testFailedAndKeepJob(): void
     {
         $handler  = new PredisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -179,7 +181,7 @@ public function testFailedAndKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testFailedAndDontKeepJob()
+    public function testFailedAndDontKeepJob(): void
     {
         $handler  = new PredisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -203,7 +205,7 @@ public function testFailedAndDontKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testDoneAndKeepJob()
+    public function testDoneAndKeepJob(): void
     {
         $handler  = new PredisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -220,7 +222,7 @@ public function testDoneAndKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testDoneAndDontKeepJob()
+    public function testDoneAndDontKeepJob(): void
     {
         $handler  = new PredisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -238,7 +240,7 @@ public function testDoneAndDontKeepJob()
     /**
      * @throws ReflectionException
      */
-    public function testClear()
+    public function testClear(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->clear('queue1');
@@ -255,7 +257,7 @@ public function testClear()
     /**
      * @throws ReflectionException
      */
-    public function testClearAll()
+    public function testClearAll(): void
     {
         $handler = new PredisHandler($this->config);
         $result  = $handler->clear();
@@ -272,7 +274,7 @@ public function testClearAll()
     /**
      * @throws ReflectionException
      */
-    public function testRetry()
+    public function testRetry(): void
     {
         $handler = new PredisHandler($this->config);
         $count   = $handler->retry(1, 'queue1');
diff --git a/tests/QueueTest.php b/tests/QueueTest.php
index 0bd655b..377dc43 100644
--- a/tests/QueueTest.php
+++ b/tests/QueueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use CodeIgniter\Queue\Exceptions\QueueException;
@@ -24,13 +26,13 @@ protected function setUp(): void
         $this->config = config(QueueConfig::class);
     }
 
-    public function testQueue()
+    public function testQueue(): void
     {
         $queue = new Queue($this->config);
         $this->assertInstanceOf(Queue::class, $queue);
     }
 
-    public function testQueueException()
+    public function testQueueException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This queue handler is incorrect.');
@@ -41,7 +43,7 @@ public function testQueueException()
         $this->assertInstanceOf(Queue::class, $queue);
     }
 
-    public function testQueueInit()
+    public function testQueueInit(): void
     {
         $queue = new Queue($this->config);
         $this->assertInstanceOf(DatabaseHandler::class, $queue->init());
diff --git a/tests/RedisHandlerTest.php b/tests/RedisHandlerTest.php
index ddc9f6a..8605b99 100644
--- a/tests/RedisHandlerTest.php
+++ b/tests/RedisHandlerTest.php
@@ -31,13 +31,13 @@ protected function setUp(): void
         $this->config = config(QueueConfig::class);
     }
 
-    public function testRedisHandler()
+    public function testRedisHandler(): void
     {
         $handler = new RedisHandler($this->config);
         $this->assertInstanceOf(RedisHandler::class, $handler);
     }
 
-    public function testPriority()
+    public function testPriority(): void
     {
         $handler = new RedisHandler($this->config);
         $handler->setPriority('high');
@@ -45,7 +45,7 @@ public function testPriority()
         $this->assertSame('high', self::getPrivateProperty($handler, 'priority'));
     }
 
-    public function testPriorityException()
+    public function testPriorityException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('The priority name should consists only lowercase letters.');
@@ -54,7 +54,7 @@ public function testPriorityException()
         $handler->setPriority('high_:');
     }
 
-    public function testPush()
+    public function testPush(): void
     {
         $handler = new RedisHandler($this->config);
         $result  = $handler->push('queue', 'success', ['key' => 'value']);
@@ -70,7 +70,7 @@ public function testPush()
         $this->assertSame(['key' => 'value'], $queueJob->payload['data']);
     }
 
-    public function testPushWithPriority()
+    public function testPushWithPriority(): void
     {
         $handler = new RedisHandler($this->config);
         $result  = $handler->setPriority('high')->push('queue', 'success', ['key' => 'value']);
@@ -86,7 +86,7 @@ public function testPushWithPriority()
         $this->assertSame(['key' => 'value'], $queueJob->payload['data']);
     }
 
-    public function testPushException()
+    public function testPushException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This job name is not defined in the $jobHandlers array.');
@@ -95,7 +95,7 @@ public function testPushException()
         $handler->push('queue', 'not-exists', ['key' => 'value']);
     }
 
-    public function testPushWithPriorityException()
+    public function testPushWithPriorityException(): void
     {
         $this->expectException(QueueException::class);
         $this->expectExceptionMessage('This queue has incorrectly defined priority: "invalid" for the queue: "queue".');
@@ -104,7 +104,7 @@ public function testPushWithPriorityException()
         $handler->setPriority('invalid')->push('queue', 'success', ['key' => 'value']);
     }
 
-    public function testPop()
+    public function testPop(): void
     {
         $handler = new RedisHandler($this->config);
         $result  = $handler->pop('queue1', ['default']);
@@ -117,7 +117,7 @@ public function testPop()
         $this->assertTrue($redis->hExists('queues:queue1::reserved', (string) $result->id));
     }
 
-    public function testPopEmpty()
+    public function testPopEmpty(): void
     {
         $handler = new RedisHandler($this->config);
         $result  = $handler->pop('queue123', ['default']);
@@ -125,7 +125,7 @@ public function testPopEmpty()
         $this->assertNull($result);
     }
 
-    public function testLater()
+    public function testLater(): void
     {
         $handler  = new RedisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -141,7 +141,7 @@ public function testLater()
         $this->assertSame(1, $redis->zCard('queues:queue1:default'));
     }
 
-    public function testFailedAndKeepJob()
+    public function testFailedAndKeepJob(): void
     {
         $handler  = new RedisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -162,7 +162,7 @@ public function testFailedAndKeepJob()
         ]);
     }
 
-    public function testFailedAndDontKeepJob()
+    public function testFailedAndDontKeepJob(): void
     {
         $handler  = new RedisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -183,7 +183,7 @@ public function testFailedAndDontKeepJob()
         ]);
     }
 
-    public function testDoneAndKeepJob()
+    public function testDoneAndKeepJob(): void
     {
         $handler  = new RedisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -197,7 +197,7 @@ public function testDoneAndKeepJob()
         $this->assertSame(1, $redis->lLen('queues:queue1::done'));
     }
 
-    public function testDoneAndDontKeepJob()
+    public function testDoneAndDontKeepJob(): void
     {
         $handler  = new RedisHandler($this->config);
         $queueJob = $handler->pop('queue1', ['default']);
@@ -212,7 +212,7 @@ public function testDoneAndDontKeepJob()
         $this->assertSame(0, $redis->lLen('queues:queue1::done'));
     }
 
-    public function testClear()
+    public function testClear(): void
     {
         $handler = new RedisHandler($this->config);
         $result  = $handler->clear('queue1');
@@ -226,7 +226,7 @@ public function testClear()
         $this->assertTrue($result);
     }
 
-    public function testClearAll()
+    public function testClearAll(): void
     {
         $handler = new RedisHandler($this->config);
 
@@ -240,7 +240,7 @@ public function testClearAll()
         $this->assertTrue($result);
     }
 
-    public function testRetry()
+    public function testRetry(): void
     {
         $handler = new RedisHandler($this->config);
         $count   = $handler->retry(1, 'queue1');
diff --git a/tests/_support/Config/Queue.php b/tests/_support/Config/Queue.php
index d71bee9..24097e2 100644
--- a/tests/_support/Config/Queue.php
+++ b/tests/_support/Config/Queue.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Config;
 
 use CodeIgniter\Queue\Config\Queue as BaseQueue;
diff --git a/tests/_support/Database/Seeds/TestDatabaseQueueSeeder.php b/tests/_support/Database/Seeds/TestDatabaseQueueSeeder.php
index 1ca323b..8bc9e14 100644
--- a/tests/_support/Database/Seeds/TestDatabaseQueueSeeder.php
+++ b/tests/_support/Database/Seeds/TestDatabaseQueueSeeder.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Database\Seeds;
 
 use CodeIgniter\Database\Seeder;
diff --git a/tests/_support/Database/Seeds/TestRedisQueueSeeder.php b/tests/_support/Database/Seeds/TestRedisQueueSeeder.php
index abaebed..ec7debb 100644
--- a/tests/_support/Database/Seeds/TestRedisQueueSeeder.php
+++ b/tests/_support/Database/Seeds/TestRedisQueueSeeder.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Database\Seeds;
 
 use CodeIgniter\Database\Seeder;
diff --git a/tests/_support/Jobs/Failure.php b/tests/_support/Jobs/Failure.php
index 737ef53..f3a6699 100644
--- a/tests/_support/Jobs/Failure.php
+++ b/tests/_support/Jobs/Failure.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Jobs;
 
 use CodeIgniter\Queue\BaseJob;
diff --git a/tests/_support/Jobs/Success.php b/tests/_support/Jobs/Success.php
index dd2125d..21a3fb9 100644
--- a/tests/_support/Jobs/Success.php
+++ b/tests/_support/Jobs/Success.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support\Jobs;
 
 use CodeIgniter\Queue\BaseJob;
diff --git a/tests/_support/TestCase.php b/tests/_support/TestCase.php
index 48f2d40..3814462 100644
--- a/tests/_support/TestCase.php
+++ b/tests/_support/TestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests\Support;
 
 use CodeIgniter\Test\CIUnitTestCase;