Update type hint in test files.

tests/test_app/TestApp/Application.php

@@ -20,7 +20,7 @@ use TestApp\Command\AbortCommand;
 
 class Application extends BaseApplication
 {
-    public function bootstrap()
+    public function bootstrap(): void
     {
         parent::bootstrap();
     }
@@ -50,7 +50,7 @@ class Application extends BaseApplication
      * @param \Cake\Routing\RouteBuilder $routes
      * @return void
      */
-    public function routes($routes)
+    public function routes($routes): void
     {
         $routes->scope('/app', function ($routes) {
             $routes->connect('/articles', ['controller' => 'Articles']);

tests/test_app/TestApp/ApplicationWithDefaultRoutes.php

@@ -34,7 +34,7 @@ class ApplicationWithDefaultRoutes extends BaseApplication
      *
      * @return void
      */
-    public function bootstrap()
+    public function bootstrap(): void
     {
         // Do nothing.
     }

tests/test_app/TestApp/ApplicationWithExceptionsInMiddleware.php

@@ -31,7 +31,7 @@ class ApplicationWithExceptionsInMiddleware extends BaseApplication
      *
      * @return void
      */
-    public function bootstrap()
+    public function bootstrap(): void
     {
         // Do nothing.
     }

tests/test_app/TestApp/ApplicationWithPluginRoutes.php

@@ -19,7 +19,7 @@ use Cake\Routing\Middleware\RoutingMiddleware;
 
 class ApplicationWithPluginRoutes extends BaseApplication
 {
-    public function bootstrap()
+    public function bootstrap(): void
     {
         parent::bootstrap();
         $this->addPlugin('TestPlugin');
@@ -38,7 +38,7 @@ class ApplicationWithPluginRoutes extends BaseApplication
      * @param \Cake\Routing\RouteBuilder $routes
      * @return void
      */
-    public function routes($routes)
+    public function routes($routes): void
     {
         $routes->scope('/app', function ($routes) {
             $routes->connect('/articles', ['controller' => 'Articles']);