Test loading kernel based on classname

features/configuration/loading_kernel_based_on_configurtion.feature

@@ -0,0 +1,97 @@
+Feature: Loading kernel based on configuration
+
+    Background:
+        Given a standard Symfony autoloader configured
+        And a feature file containing:
+        """
+        Feature:
+            Scenario:
+                Then the passed service should be an instance of "\Psr\Container\ContainerInterface"
+        """
+        And a Behat configuration containing:
+        """
+        default:
+            suites:
+                default:
+                    contexts:
+                        - App\Tests\SomeContext
+        """
+        And a context file "tests/SomeContext.php" containing:
+        """
+        <?php
+
+        namespace App\Tests;
+
+        use Behat\Behat\Context\Context;
+
+        final class SomeContext implements Context {
+            private $service;
+
+            public function __construct($service = null) { $this->service = $service; }
+
+            /** @Then the passed service should be an instance of :expected */
+            public function serviceShouldBe(string $expected): void
+            {
+                assert(is_object($this->service));
+                assert($this->service instanceof $expected);
+            }
+        }
+        """
+        And a services file "config/services.yaml" containing:
+        """
+        services:
+            App\Tests\SomeContext:
+                public: true
+                arguments:
+                    - "@service_container"
+        """
+
+    Scenario: Loading kernel by its classname
+        Given a Behat configuration containing:
+        """
+        default:
+            extensions:
+                FriendsOfBehat\SymfonyExtension:
+                    kernel:
+                        class: App\Custom\Kernel
+        """
+        And a kernel file "src/Custom/Kernel.php" containing:
+        """
+        <?php
+
+        namespace App\Custom;
+
+        use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+        use Symfony\Component\Config\Loader\LoaderInterface;
+        use Symfony\Component\DependencyInjection\ContainerBuilder;
+        use Symfony\Component\HttpFoundation\Response;
+        use Symfony\Component\HttpKernel\Kernel as HttpKernel;
+        use Symfony\Component\Routing\RouteCollectionBuilder;
+
+        class Kernel extends HttpKernel
+        {
+            use MicroKernelTrait;
+
+            public function registerBundles(): iterable
+            {
+                return [
+                    new \Symfony\Bundle\FrameworkBundle\FrameworkBundle(),
+                    new \FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle(),
+                ];
+            }
+
+            protected function configureContainer(ContainerBuilder $container, LoaderInterface $loader): void
+            {
+                $container->loadFromExtension('framework', [
+                    'test' => $this->getEnvironment() === 'test',
+                    'secret' => 'Pigeon',
+                ]);
+
+                $loader->load(__DIR__ . '/../../config/services.yaml');
+            }
+
+            protected function configureRoutes(RouteCollectionBuilder $routes): void {}
+        }
+        """
+        When I run Behat
+        Then it should pass

tests/Behat/Context/TestContext.php

@@ -51,6 +51,25 @@ final class TestContext implements Context
         self::$filesystem->remove(self::$workingDir);
     }
 
+    /**
+     * @Given a standard Symfony autoloader configured
+     */
+    public function standardSymfonyAutoloaderConfigured(): void
+    {
+        $this->thereIsFile('vendor/autoload.php', sprintf(<<<'CON'
+<?php
+
+declare(strict_types=1);
+
+$loader = require '%s';
+$loader->addPsr4('App\\', __DIR__ . '/../src/');
+$loader->addPsr4('App\\Tests\\', __DIR__ . '/../tests/');
+
+return $loader; 
+CON
+            , __DIR__ . '/../../../vendor/autoload.php'));
+    }
+
     /**
      * @Given a working Symfony application with SymfonyExtension configured
      */
@@ -65,18 +84,7 @@ default:
 CON
         );
 
-        $this->thereIsFile('vendor/autoload.php', sprintf(<<<'CON'
-<?php
-
-declare(strict_types=1);
-
-$loader = require '%s';
-$loader->addPsr4('App\\', __DIR__ . '/../src/');
-$loader->addPsr4('App\\Tests\\', __DIR__ . '/../tests/');
-
-return $loader; 
-CON
-        , __DIR__ . '/../../../vendor/autoload.php'));
+        $this->standardSymfonyAutoloaderConfigured();
 
         $this->thereIsFile('src/Kernel.php', <<<'CON'
 <?php