might have fixed the issue

dev_mvc/controller/MVCController.php

@@ -69,8 +69,8 @@ class MVCController{
 		//check if testaction is valid
 		if(file_exists($this->testaction)){
 			//execute testaction
-			require_once($this->testaction);
+			//require_once($this->testaction);
-			$testactionClassname = "TA_".$_POST['testaction'];
+			$testactionClassname = "model\testactions\\". "TA_".$_POST['testaction'];
 			$testactionInstance = new $testactionClassname();
 		}
     	

dev_mvc/model/testactions/TA_CreateDB.php

@@ -1,6 +1,7 @@
 <?php
 namespace model\testactions;
 use PDO;
+use PDOException;
 class TA_CreateDB extends TestAction{
     function TA_CreateDB(){
         

dev_mvc/model/testactions/TA_PopulateDB.php

@@ -1,6 +1,8 @@
 <?php
 namespace model\testactions;
 use controller\db\Database;
+use PDO;
+use PDOException;
 class TA_PopulateDB extends TestAction{
     function TA_PopulateDB(){
         parent::__construct();

dev_mvc/model/testactions/TA_TestSQLConnection.php

@@ -1,5 +1,6 @@
 <?php
 namespace model\testactions;
+use PDO;
 class TA_TestSQLConnection extends TestAction{
     function __construct(){
         parent::__construct();