Explicitly fail for undirected edges

Author: clue

lib/Fhaculty/Graph/Algorithm/MinimumCostFlow/SuccessiveShortestPath.php

@@ -36,6 +36,10 @@ public function createGraph()
         // initial flow of edges
         $edges = $resultGraph->getEdges();
         foreach ($edges as $edge) {
+            if (!($edge instanceof EdgeDirected)) {
+                throw new UnexpectedValueException('Undirected edges are not supported for SuccessiveShortestPath');
+            }
+
             // 0 if weight of edge is positive
             $flow = 0;
 

tests/Fhaculty/Graph/Algorithm/MinimumCostFlow/BaseMcfTest.php

@@ -163,4 +163,19 @@ public function testUndirectedFails()
         $alg = $this->createAlgorithm($graph);
         $alg->getWeightFlow();
     }
+
+    /**
+     * @expectedException UnexpectedValueException
+     */
+    public function testUndirectedNegativeCycleFails()
+    {
+        // 1(+2) -[0/2/-1]- 2(-2)
+        $graph = new Graph();
+        $v1 = $graph->createVertex(1)->setBalance(2);
+        $v2 = $graph->createVertex(2)->setBalance(-2);
+        $v1->createEdge($v2)->setCapacity(2)->setWeight(-1);
+
+        $alg = $this->createAlgorithm($graph);
+        $alg->getWeightFlow();
+    }
 }