diff --git a/App.php b/App.php
index 824e541..f6dedbe 100644
--- a/App.php
+++ b/App.php
@@ -11,6 +11,7 @@ use Exception;
 use Pico;
 use SeacmsAppPlugin;
 use SeaCMS\Api\SpecialOutputException;
+use SeaCMS\App\TestInterface;
 use Throwable;
 
 set_error_handler(function (
@@ -51,7 +52,7 @@ class App
      */
     protected $pico;
 
-    public function __construct(string $contentFolderFromRoot)
+    public function __construct(string $contentFolderFromRoot, ?TestInterface $testRunner = null)
     {
         // sanitize content folder
         $cwd = getcwd();
@@ -76,7 +77,7 @@ class App
             self::PLUGINS_PATH, // plugins dir
             self::THEMES_PATH   // themes dir
         );
-        $this->pico->loadPlugin(new SeacmsAppPlugin($this->pico));
+        $this->pico->loadPlugin(new SeacmsAppPlugin($this->pico, $testRunner));
         $this->update_SERVERIfNeeded($this->pico, $contentFolderFromRoot);
     }
 
diff --git a/SeacmsAppPlugin.php b/SeacmsAppPlugin.php
index 73db11f..fb8b36d 100644
--- a/SeacmsAppPlugin.php
+++ b/SeacmsAppPlugin.php
@@ -5,6 +5,7 @@
 use SeaCMS\Api\LateApiAware;
 use SeaCMS\Api\JsonResponse;
 use SeaCMS\App\MdResponse;
+use SeaCMS\App\TestInterface;
 
 /**
  * A plugin for SeaCMS-app.
@@ -17,6 +18,30 @@ class SeacmsAppPlugin extends AbstractPicoPlugin implements LateApiAware
      */
     const API_VERSION = 4;
 
+    /**
+     * define if test output should be defined
+     * @var bool
+     */
+    protected $triggerTest;
+
+    /**
+     * define test
+     * @var TestInterface
+     */
+    protected $testRunner;
+
+    /** 
+     * construct
+     * @param Pico $pico current instance of Pico
+     * @param ?TestInterface $testRunner optional
+     */
+    public function __construct(Pico $pico, $testRunner = null)
+    {
+        parent::__construct($pico);
+        $this->triggerTest = !empty($testRunner) && ($testRunner instanceof TestInterface);
+        $this->testRunner = ($this->triggerTest) ? $testRunner : null;
+    }
+
     /**
      * return api routes
      * @return array
@@ -136,4 +161,16 @@ class SeacmsAppPlugin extends AbstractPicoPlugin implements LateApiAware
         return $this->apiPageAsMd("$folder1/$folder2/$folder3/$pageName");
     }
 
+    /**
+     * Triggered after Pico has rendered the page
+     *
+     * @param string &$output contents which will be sent to the user
+     */
+    public function onPageRendered(&$output)
+    {
+        if ($this->triggerTest){
+            $this->testRunner->run($this,$output);
+        }
+    }
+
 }
\ No newline at end of file
diff --git a/src/TestException.php b/src/TestException.php
new file mode 100644
index 0000000..1345f48
--- /dev/null
+++ b/src/TestException.php
@@ -0,0 +1,14 @@
+<?php
+// SPDX-License-Identifier: EUPL-1.2
+// Authors: see README.md
+
+namespace SeaCMS\App;
+
+use Exception;
+use SeaCMS\App\TestException;
+
+/**
+ * define exception to caught return for tests
+ */
+class TestException extends Exception
+{}
diff --git a/src/TestInterface.php b/src/TestInterface.php
new file mode 100644
index 0000000..121eba1
--- /dev/null
+++ b/src/TestInterface.php
@@ -0,0 +1,22 @@
+<?php
+// SPDX-License-Identifier: EUPL-1.2
+// Authors: see README.md
+
+namespace SeaCMS\App;
+
+use SeacmsAppPlugin;
+use SeaCMS\App\TestException;
+
+/**
+ * define interface for tests
+ */
+interface TestInterface
+{
+    /**
+     * run tests
+     * @param SeacmsAppPlugin $plugin
+     * @param string $output
+     * @throws TestException
+     */
+    public function run(SeacmsAppPlugin $plugin, string $output);
+}
diff --git a/tests/AppTest.php b/tests/AppTest.php
new file mode 100644
index 0000000..f207b99
--- /dev/null
+++ b/tests/AppTest.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * SPDX-License-Identifier: EUPL-1.2
+ * Authors: see /README.md
+ */
+
+namespace SeaCMS\App\Test;
+
+use SeaCMS\App;
+use PHPUnit\Framework\TestCase;
+
+final class AppTest extends TestCase {
+
+    public function testSuccess(): void
+    {
+        $app = new App('');
+        $output = $app->runPico();
+        $this->assertTrue($app instanceof App);
+    }
+    public function testFailure(): void
+    {
+        $this->assertTrue(false);
+    }
+}
\ No newline at end of file