diff --git a/src/Exception/MissingPackageException.php b/src/Exception/MissingPackageException.php
index b1ea8bb..c00462d 100644
--- a/src/Exception/MissingPackageException.php
+++ b/src/Exception/MissingPackageException.php
@@ -16,7 +16,7 @@
  */
 final class MissingPackageException extends \RuntimeException
 {
-    public function __construct($message = '', \Throwable $previous = null)
+    public function __construct(string $message = '', \Throwable $previous = null)
     {
         parent::__construct($message, 0, $previous);
     }
diff --git a/src/Lazy/LazyFactory.php b/src/Lazy/LazyFactory.php
index 782bacf..48dfc28 100644
--- a/src/Lazy/LazyFactory.php
+++ b/src/Lazy/LazyFactory.php
@@ -11,6 +11,7 @@
 
 namespace League\FlysystemBundle\Lazy;
 
+use League\Flysystem\FilesystemOperator;
 use Psr\Container\ContainerInterface;
 
 /**
@@ -27,7 +28,7 @@ public function __construct(ContainerInterface $storages)
         $this->storages = $storages;
     }
 
-    public function createStorage(string $source, string $storageName)
+    public function createStorage(string $source, string $storageName): FilesystemOperator
     {
         if ($source === $storageName) {
             throw new \InvalidArgumentException('The "lazy" adapter source is referring to itself as "'.$source.'", which would lead to infinite recursion.');
diff --git a/tests/Adapter/AdapterDefinitionFactoryTest.php b/tests/Adapter/AdapterDefinitionFactoryTest.php
index dc7d531..fb75ff2 100644
--- a/tests/Adapter/AdapterDefinitionFactoryTest.php
+++ b/tests/Adapter/AdapterDefinitionFactoryTest.php
@@ -30,7 +30,7 @@ public function provideConfigOptions(): \Generator
     /**
      * @dataProvider provideConfigOptions
      */
-    public function testCreateDefinition($name, $options)
+    public function testCreateDefinition($name, $options): void
     {
         $factory = new AdapterDefinitionFactory();
 
diff --git a/tests/Adapter/Builder/AsyncAwsAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/AsyncAwsAdapterDefinitionBuilderTest.php
index 4eb93fb..e13af2c 100644
--- a/tests/Adapter/Builder/AsyncAwsAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/AsyncAwsAdapterDefinitionBuilderTest.php
@@ -41,7 +41,7 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $definition = $this->createBuilder()->createDefinition($options, Visibility::PRIVATE);
         $this->assertSame(AsyncAwsS3Adapter::class, $definition->getClass());
diff --git a/tests/Adapter/Builder/AwsAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/AwsAdapterDefinitionBuilderTest.php
index a32a091..377414e 100644
--- a/tests/Adapter/Builder/AwsAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/AwsAdapterDefinitionBuilderTest.php
@@ -49,12 +49,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(AwsS3V3Adapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $definition = $this->createBuilder()->createDefinition([
             'client' => 'my_client',
diff --git a/tests/Adapter/Builder/AzureAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/AzureAdapterDefinitionBuilderTest.php
index 3493d6c..13babc4 100644
--- a/tests/Adapter/Builder/AzureAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/AzureAdapterDefinitionBuilderTest.php
@@ -40,12 +40,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(AzureBlobStorageAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $definition = $this->createBuilder()->createDefinition([
             'client' => 'my_client',
diff --git a/tests/Adapter/Builder/FtpAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/FtpAdapterDefinitionBuilderTest.php
index 30e60f4..fe72893 100644
--- a/tests/Adapter/Builder/FtpAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/FtpAdapterDefinitionBuilderTest.php
@@ -48,12 +48,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(FtpAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $definition = $this->createBuilder()->createDefinition([
             'host' => 'ftp.example.com',
diff --git a/tests/Adapter/Builder/GcloudAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/GcloudAdapterDefinitionBuilderTest.php
index 3d54487..9dc3b42 100644
--- a/tests/Adapter/Builder/GcloudAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/GcloudAdapterDefinitionBuilderTest.php
@@ -55,12 +55,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(GoogleCloudStorageAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $definition = $this->createBuilder()->createDefinition([
             'client' => 'my_client',
diff --git a/tests/Adapter/Builder/GridFSAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/GridFSAdapterDefinitionBuilderTest.php
index c7ea289..91c361b 100644
--- a/tests/Adapter/Builder/GridFSAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/GridFSAdapterDefinitionBuilderTest.php
@@ -60,7 +60,7 @@ public static function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(GridFSAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
@@ -86,7 +86,7 @@ public static function provideInvalidOptions(): \Generator
     /**
      * @dataProvider provideInvalidOptions
      */
-    public function testInvalidOptions(array $options, string $message)
+    public function testInvalidOptions(array $options, string $message): void
     {
         $builder = $this->createBuilder();
 
@@ -96,7 +96,7 @@ public function testInvalidOptions(array $options, string $message)
         $builder->createDefinition($options, null);
     }
 
-    public function testInitializeBucketFromDocumentManager()
+    public function testInitializeBucketFromDocumentManager(): void
     {
         $client = new Client();
         $config = new Configuration();
@@ -112,7 +112,7 @@ public function testInitializeBucketFromDocumentManager()
         $this->assertSame('avatars', $bucket->getBucketName());
     }
 
-    public function testInitializeBucketFromConfig()
+    public function testInitializeBucketFromConfig(): void
     {
         $bucket = GridFSAdapterDefinitionBuilder::initializeBucketFromConfig(
             'mongodb://server:27017/',
diff --git a/tests/Adapter/Builder/LocalAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/LocalAdapterDefinitionBuilderTest.php
index 1b6998a..2bae698 100644
--- a/tests/Adapter/Builder/LocalAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/LocalAdapterDefinitionBuilderTest.php
@@ -88,12 +88,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(LocalFilesystemAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $permissions = [
             'file' => [
diff --git a/tests/Adapter/Builder/MemoryAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/MemoryAdapterDefinitionBuilderTest.php
index aa24cf9..1ac9633 100644
--- a/tests/Adapter/Builder/MemoryAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/MemoryAdapterDefinitionBuilderTest.php
@@ -22,7 +22,7 @@ public function createBuilder(): MemoryAdapterDefinitionBuilder
         return new MemoryAdapterDefinitionBuilder();
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $this->assertSame(InMemoryFilesystemAdapter::class, $this->createBuilder()->createDefinition([], null)->getClass());
     }
diff --git a/tests/Adapter/Builder/SftpAdapterDefinitionBuilderTest.php b/tests/Adapter/Builder/SftpAdapterDefinitionBuilderTest.php
index c09a735..a1462b5 100644
--- a/tests/Adapter/Builder/SftpAdapterDefinitionBuilderTest.php
+++ b/tests/Adapter/Builder/SftpAdapterDefinitionBuilderTest.php
@@ -46,12 +46,12 @@ public function provideValidOptions(): \Generator
     /**
      * @dataProvider provideValidOptions
      */
-    public function testCreateDefinition($options)
+    public function testCreateDefinition($options): void
     {
         $this->assertSame(SftpAdapter::class, $this->createBuilder()->createDefinition($options, null)->getClass());
     }
 
-    public function testOptionsBehavior()
+    public function testOptionsBehavior(): void
     {
         $definition = $this->createBuilder()->createDefinition([
             'host' => 'ftp.example.com',
diff --git a/tests/DependencyInjection/FlysystemExtensionTest.php b/tests/DependencyInjection/FlysystemExtensionTest.php
index 20434ac..814cafb 100644
--- a/tests/DependencyInjection/FlysystemExtensionTest.php
+++ b/tests/DependencyInjection/FlysystemExtensionTest.php
@@ -24,7 +24,7 @@
 
 class FlysystemExtensionTest extends TestCase
 {
-    public function provideFilesystems()
+    public function provideFilesystems(): \Generator
     {
         $fsNames = [
             'fs_aws',
@@ -45,7 +45,7 @@ public function provideFilesystems()
     /**
      * @dataProvider provideFilesystems
      */
-    public function testFilesystems(string $fsName)
+    public function testFilesystems(string $fsName): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
@@ -58,7 +58,7 @@ public function testFilesystems(string $fsName)
     /**
      * @dataProvider provideFilesystems
      */
-    public function testTaggedCollection(string $fsName)
+    public function testTaggedCollection(string $fsName): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
@@ -72,7 +72,7 @@ public function testTaggedCollection(string $fsName)
         $this->assertInstanceOf(FilesystemOperator::class, $storages[$fsName]);
     }
 
-    public function testPublicUrl()
+    public function testPublicUrl(): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
@@ -82,7 +82,7 @@ public function testPublicUrl()
         self::assertSame('https://example.org/assets/test1.txt', $fs->publicUrl('test1.txt'));
     }
 
-    public function testPublicUrls()
+    public function testPublicUrls(): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
@@ -94,7 +94,7 @@ public function testPublicUrls()
         self::assertSame('https://cdn3.example.org/yww/test1.txt', $fs->publicUrl('yww/test1.txt'));
     }
 
-    public function testUrlGenerators()
+    public function testUrlGenerators(): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
@@ -105,7 +105,7 @@ public function testUrlGenerators()
         self::assertSame('https://example.org/temporary/test1.txt?expiresAt=1670846026', $fs->temporaryUrl('test1.txt', new \DateTimeImmutable('@1670846026')));
     }
 
-    public function testReadOnly()
+    public function testReadOnly(): void
     {
         $kernel = $this->createFysystemKernel();
         $container = $kernel->getContainer()->get('test.service_container');
diff --git a/tests/FlysystemBundleTest.php b/tests/FlysystemBundleTest.php
index dadcda5..8b4bd73 100644
--- a/tests/FlysystemBundleTest.php
+++ b/tests/FlysystemBundleTest.php
@@ -27,7 +27,7 @@ public function provideKernels(): \Generator
     /**
      * @dataProvider provideKernels
      */
-    public function testBootKernel(Kernel $kernel)
+    public function testBootKernel(Kernel $kernel): void
     {
         $kernel->boot();
         $this->assertArrayHasKey('FlysystemBundle', $kernel->getBundles());