diff --git a/flight/commands/AiGenerateInstructionsCommand.php b/flight/commands/AiGenerateInstructionsCommand.php
index cb78e9a..5190c3c 100644
--- a/flight/commands/AiGenerateInstructionsCommand.php
+++ b/flight/commands/AiGenerateInstructionsCommand.php
@@ -33,7 +33,7 @@ class AiGenerateInstructionsCommand extends AbstractBaseCommand
      *
      * @return int
      */
-    public function execute()
+    public function execute(): int
     {
         $io = $this->app()->io();
 
diff --git a/flight/commands/AiInitCommand.php b/flight/commands/AiInitCommand.php
index f24332d..92b468d 100644
--- a/flight/commands/AiInitCommand.php
+++ b/flight/commands/AiInitCommand.php
@@ -27,7 +27,7 @@ class AiInitCommand extends AbstractBaseCommand
      *
      * @return int
      */
-    public function execute()
+    public function execute(): int
     {
         $io = $this->app()->io();
 
diff --git a/flight/commands/ControllerCommand.php b/flight/commands/ControllerCommand.php
index a7c10bc..e61dada 100644
--- a/flight/commands/ControllerCommand.php
+++ b/flight/commands/ControllerCommand.php
@@ -26,7 +26,7 @@ class ControllerCommand extends AbstractBaseCommand
      *
      * @return void
      */
-    public function execute(string $controller)
+    public function execute(string $controller): void
     {
         $io = $this->app()->io();
 
diff --git a/flight/commands/RouteCommand.php b/flight/commands/RouteCommand.php
index d742708..1667934 100644
--- a/flight/commands/RouteCommand.php
+++ b/flight/commands/RouteCommand.php
@@ -37,7 +37,7 @@ class RouteCommand extends AbstractBaseCommand
      *
      * @return void
      */
-    public function execute()
+    public function execute(): void
     {
         $io = $this->app()->io();
 
diff --git a/flight/net/Request.php b/flight/net/Request.php
index 6e9aa93..31ff1b9 100644
--- a/flight/net/Request.php
+++ b/flight/net/Request.php
@@ -375,7 +375,7 @@ class Request
      *
      * @return string
      */
-    public static function header(string $header, $default = '')
+    public static function header(string $header, $default = ''): string
     {
         return self::getHeader($header, $default);
     }
diff --git a/tests/EngineTest.php b/tests/EngineTest.php
index 91e9f3b..bdb5302 100644
--- a/tests/EngineTest.php
+++ b/tests/EngineTest.php
@@ -52,7 +52,7 @@ class EngineTest extends TestCase
 	public function testInitBeforeStartV2OutputBuffering(): void
     {
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -122,7 +122,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -141,7 +141,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -160,7 +160,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -180,7 +180,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -207,7 +207,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -254,7 +254,7 @@ class EngineTest extends TestCase
         $_SERVER['REQUEST_URI'] = '/someRoute';
 
         $engine = new class extends Engine {
-            public function getInitializedVar()
+            public function getInitializedVar(): bool
             {
                 return $this->initialized;
             }
@@ -276,7 +276,7 @@ class EngineTest extends TestCase
         $engine->start();
     }
 
-	public function testDoubleStart() 
+	public function testDoubleStart(): void
     {
 		$engine = new Engine();
 		$engine->route('/someRoute', function () {
@@ -512,7 +512,7 @@ class EngineTest extends TestCase
 		$this->assertEquals('{"key1":"value1","key2":"value2","utf8_emoji":"😀"}', $engine->response()->getBody());
 	}
 
-	public function testJsonThrowOnErrorByDefault()
+	public function testJsonThrowOnErrorByDefault(): void
 	{
 		$engine = new Engine();
 		$this->expectException(Exception::class);
@@ -1000,7 +1000,7 @@ class EngineTest extends TestCase
         $engine->start();
     }
 
-    public function testContainerPsr11() {
+    public function testContainerPsr11(): void {
         $engine = new Engine();
         $container = new \League\Container\Container();
         $container->add(Container::class)->addArgument(Collection::class)->addArgument(PdoWrapper::class);
@@ -1031,7 +1031,7 @@ class EngineTest extends TestCase
         $engine->start();
     }
 
-    public function testContainerPsr11MethodNotFound() {
+    public function testContainerPsr11MethodNotFound(): void {
         $engine = new Engine();
         $container = new \League\Container\Container();
         $container->add(Container::class)->addArgument(Collection::class)->addArgument(PdoWrapper::class);
@@ -1048,7 +1048,7 @@ class EngineTest extends TestCase
         $engine->start();
     }
 
-	public function testRouteFoundButBadMethod() {
+	public function testRouteFoundButBadMethod(): void {
         $engine = new class extends Engine {
             public function getLoader()
             {
diff --git a/tests/RouterTest.php b/tests/RouterTest.php
index c0ed3c1..620ecc3 100644
--- a/tests/RouterTest.php
+++ b/tests/RouterTest.php
@@ -39,7 +39,7 @@ class RouterTest extends TestCase
     }
 
     // Checks if a route was matched with a given output
-    public function check($str = '')
+    public function check($str = ''): void
     {
 
         /*$route = $this->router->route($this->request);
@@ -502,7 +502,7 @@ class RouterTest extends TestCase
     {
         $router = new class extends Router
         {
-            public function getIndex()
+            public function getIndex(): int
             {
                 return $this->index;
             }
diff --git a/tests/UploadedFileTest.php b/tests/UploadedFileTest.php
index 9a531f5..f8817f3 100644
--- a/tests/UploadedFileTest.php
+++ b/tests/UploadedFileTest.php
@@ -55,7 +55,7 @@ class UploadedFileTest extends TestCase
     /**
      * @dataProvider getFileErrorMessageTests
      */
-    public function testMoveToFailureMessages($error, $message)
+    public function testMoveToFailureMessages(int $error, string $message): void
     {
         file_put_contents('tmp_name', 'test');
         $uploadedFile = new UploadedFile('file.txt', 'text/plain', 4, 'tmp_name', $error);