Throw Exceptions for parallel edges

Author: clue

src/Tree/BaseDirected.php

@@ -49,6 +49,9 @@ public function isTree()
         catch (UnderflowException $e) {
             return false;
         }
+        catch (UnexpectedValueException $e) {
+            return false;
+        }
 
         try {
             $num = count($this->getVerticesSubtree($root));
@@ -86,6 +89,7 @@ public function getVertexParent(Vertex $vertex)
      *
      * @param Vertex $vertex
      * @return Vertex[]
+     * @throws UnexpectedValueException if the given $vertex contains invalid / parallel links (check isTree()!)
      */
     abstract public function getVerticesChildren(Vertex $vertex);
 

src/Tree/InTree.php

@@ -15,11 +15,21 @@ class InTree extends DirectedTree
 {
     public function getVerticesChildren(Vertex $vertex)
     {
-        return $vertex->getVerticesEdgeFrom();
+        $vertices = $vertex->getVerticesEdgeFrom();
+        if (count($vertices) !== $vertex->getDegreeIn()) {
+            throw new UnexpectedValueException();
+        }
+
+        return $vertices;
     }
 
     protected function getVerticesParent(Vertex $vertex)
     {
-        return $vertex->getVerticesEdgeTo();
+        $vertices = $vertex->getVerticesEdgeTo();
+        if (count($vertices) !== $vertex->getDegreeOut()) {
+            throw new UnexpectedValueException();
+        }
+
+        return $vertices;
     }
 }

src/Tree/OutTree.php

@@ -16,11 +16,21 @@ class OutTree extends DirectedTree
 {
     public function getVerticesChildren(Vertex $vertex)
     {
-        return $vertex->getVerticesEdgeTo();
+        $vertices = $vertex->getVerticesEdgeTo();
+        if (count($vertices) !== $vertex->getDegreeOut()) {
+            throw new UnexpectedValueException();
+        }
+
+        return $vertices;
     }
 
     protected function getVerticesParent(Vertex $vertex)
     {
-        return $vertex->getVerticesEdgeFrom();
+        $vertices = $vertex->getVerticesEdgeFrom();
+        if (count($vertices) !== $vertex->getDegreeIn()) {
+            throw new UnexpectedValueException();
+        }
+
+        return $vertices;
     }
 }