Added more unit tests for the graph utilities.
diff --git a/utils/misc/src/test/java/org/onlab/graph/TestVertex.java b/utils/misc/src/test/java/org/onlab/graph/TestVertex.java
index 2a1c7da..0cd8f2a 100644
--- a/utils/misc/src/test/java/org/onlab/graph/TestVertex.java
+++ b/utils/misc/src/test/java/org/onlab/graph/TestVertex.java
@@ -16,11 +16,6 @@
     }
 
     @Override
-    public String toString() {
-        return toStringHelper(this).add("name", name).toString();
-    }
-
-    @Override
     public int hashCode() {
         return Objects.hash(name);
     }
@@ -34,4 +29,9 @@
         return false;
     }
 
+    @Override
+    public String toString() {
+        return name;
+    }
+
 }