diff --git a/system/CodeIgniter.php b/system/CodeIgniter.php
index 5e54824a1a32..9d58c4f0f99f 100644
--- a/system/CodeIgniter.php
+++ b/system/CodeIgniter.php
@@ -326,6 +326,7 @@ public function run(RouteCollectionInterface $routes = null, bool $returnRespons
 
 			$this->response->pretend($this->useSafeOutput)->send();
 			$this->callExit(EXIT_SUCCESS);
+			return;
 		}
 
 		try
@@ -343,6 +344,7 @@ public function run(RouteCollectionInterface $routes = null, bool $returnRespons
 			$this->sendResponse();
 
 			$this->callExit(EXIT_SUCCESS);
+			return;
 		}
 		catch (PageNotFoundException $e)
 		{
diff --git a/system/Test/CIUnitTestCase.php b/system/Test/CIUnitTestCase.php
index c8d312b1c7f6..28418767082c 100644
--- a/system/Test/CIUnitTestCase.php
+++ b/system/Test/CIUnitTestCase.php
@@ -20,8 +20,12 @@
 use CodeIgniter\Events\Events;
 use CodeIgniter\Session\Handlers\ArrayHandler;
 use CodeIgniter\Test\Mock\MockCache;
+use CodeIgniter\Test\Mock\MockCodeIgniter;
 use CodeIgniter\Test\Mock\MockEmail;
 use CodeIgniter\Test\Mock\MockSession;
+use Config\App;
+use Config\Autoload;
+use Config\Modules;
 use Config\Services;
 use Exception;
 use PHPUnit\Framework\TestCase;
@@ -547,9 +551,13 @@ public function seeNumRecords(int $expected, string $table, array $where)
 	 */
 	protected function createApplication()
 	{
-		$path = __DIR__ . '/../bootstrap.php';
-		$path = realpath($path) ?: $path;
-		return require $path;
+		// Initialize the autoloader.
+		Services::autoloader()->initialize(new Autoload(), new Modules());
+
+		$app = new MockCodeIgniter(new App());
+		$app->initialize();
+
+		return $app;
 	}
 
 	/**
diff --git a/system/Test/bootstrap.php b/system/Test/bootstrap.php
index 0fc476d3f731..9625506bc22f 100644
--- a/system/Test/bootstrap.php
+++ b/system/Test/bootstrap.php
@@ -9,6 +9,7 @@
  * file that was distributed with this source code.
  */
 
+use CodeIgniter\Config\DotEnv;
 use CodeIgniter\Router\RouteCollection;
 use CodeIgniter\Services;
 use Config\Autoload;
@@ -83,10 +84,33 @@
 	class_alias('Config\Services', 'CodeIgniter\Services');
 }
 
-// Launch the autoloader to gather namespaces (includes composer.json's "autoload-dev")
-$loader = Services::autoloader();
-$loader->initialize(new Autoload(), new Modules());
-$loader->register(); // Register the loader with the SPL autoloader stack.
+// Initialize and register the loader with the SPL autoloader stack.
+Services::autoloader()->initialize(new Autoload(), new Modules())->register();
+
+// Now load Composer's if it's available
+if (is_file(COMPOSER_PATH))
+{
+	/*
+	 * The path to the vendor directory.
+	 *
+	 * We do not want to enforce this, so set the constant if Composer was used.
+	 */
+	if (! defined('VENDORPATH'))
+	{
+		define('VENDORPATH', realpath(ROOTPATH . 'vendor') . DIRECTORY_SEPARATOR);
+	}
+
+	require_once COMPOSER_PATH;
+}
+
+// Load environment settings from .env files into $_SERVER and $_ENV
+require_once SYSTEMPATH . 'Config/DotEnv.php';
+
+$env = new DotEnv(ROOTPATH);
+$env->load();
+
+// Always load the URL helper, it should be used in most of apps.
+helper('url');
 
 require_once APPPATH . 'Config/Routes.php';