diff --git a/tests/Model/BasePHPElement.php b/tests/Model/BasePHPElement.php
index ef055281..e32cbee9 100644
--- a/tests/Model/BasePHPElement.php
+++ b/tests/Model/BasePHPElement.php
@@ -3,9 +3,6 @@ declare(strict_types=1);
 
 namespace StubTests\Model;
 
-use PhpParser\Node\Stmt\Namespace_;
-use PhpParser\NodeAbstract;
-
 abstract class BasePHPElement
 {
     public $name;
@@ -28,16 +25,6 @@ abstract class BasePHPElement
 
     abstract public function readMutedProblems($jsonData);
 
-    protected function getConstantFQN(NodeAbstract $node, string $nodeName): string
-    {
-        $namespace = '';
-        if ($node->getAttribute('parent') instanceof Namespace_ && !empty($node->getAttribute('parent')->name)) {
-            $namespace = '\\' . implode('\\', $node->getAttribute('parent')->name->parts) . '\\';
-        }
-
-        return $namespace . $nodeName;
-    }
-
     protected function getFQN($node): string
     {
         $fqn = '';
diff --git a/tests/Model/PHPConst.php b/tests/Model/PHPConst.php
index baa00c78..5f9640ae 100644
--- a/tests/Model/PHPConst.php
+++ b/tests/Model/PHPConst.php
@@ -5,6 +5,8 @@ namespace StubTests\Model;
 
 use PhpParser\Node\Const_;
 use PhpParser\Node\Stmt\ClassConst;
+use PhpParser\Node\Stmt\Namespace_;
+use PhpParser\NodeAbstract;
 use ReflectionClassConstant;
 use stdClass;
 
@@ -55,6 +57,17 @@ class PHPConst extends BasePHPElement
         return null;
     }
 
+    protected function getConstantFQN(NodeAbstract $node, string $nodeName): string
+    {
+        $namespace = '';
+        $parentParentNode = $node->getAttribute('parent')->getAttribute('parent');
+        if ($parentParentNode instanceof Namespace_ && !empty($parentParentNode->name)) {
+            $namespace = '\\' . implode('\\', $parentParentNode->name->parts) . '\\';
+        }
+
+        return $namespace . $nodeName;
+    }
+
     public function readMutedProblems($jsonData): void
     {
         /**@var stdClass $constant */
diff --git a/tests/Model/StubsContainer.php b/tests/Model/StubsContainer.php
index 5e6d68b0..ed9bc7ce 100644
--- a/tests/Model/StubsContainer.php
+++ b/tests/Model/StubsContainer.php
@@ -37,6 +37,9 @@ class StubsContainer
      */
     public function addConstant(PHPConst $constant): void
     {
+        if (array_key_exists($constant->name, $this->constants)) {
+            throw new \Exception($constant->name . " is already defined in stubs");
+        }
         $this->constants[$constant->name] = $constant;
     }
 
@@ -82,6 +85,9 @@ class StubsContainer
      */
     public function addClass(PHPClass $class): void
     {
+        if (array_key_exists($class->name, $this->classes)) {
+            throw new \Exception($class->name . " is already defined in stubs");
+        }
         $this->classes[$class->name] = $class;
     }
 
@@ -111,6 +117,9 @@ class StubsContainer
      */
     public function addInterface(PHPInterface $interface): void
     {
+        if (array_key_exists($interface->name, $this->interfaces)) {
+            throw new \Exception($interface->name . " is already defined in stubs");
+        }
         $this->interfaces[$interface->name] = $interface;
     }
 }