Fixed 'sinks' method for undirected graph

lib/graph.js

@@ -114,7 +114,6 @@ class Graph {
     return this._label;
   }
 
-
   /* === Node functions ========== */
 
   /**
@@ -165,7 +164,14 @@ class Graph {
    */
   sinks() {
     var self = this;
-    return this.nodes().filter(v => Object.keys(self._out[v]).length === 0);
+    return this.nodes().filter(v => {
+      let isEmpty = Object.keys(self._out[v]).length === 0;
+      if (self._isDirected) {
+        isEmpty = isEmpty && Object.keys(self._in[v]).length === 0;
+      }
+
+      return isEmpty;
+    });
   }
 
   /**

test/graph-test.js

@@ -2,9 +2,13 @@
 
 describe("Graph", function() {
   var g;
+  var gUndirected;
 
   beforeEach(function() {
     g = new Graph();
+  	gUndirected = new Graph({
+		directed: false
+	});
   });
 
   describe("initial state", function() {
@@ -80,11 +84,17 @@
   });
 
   describe("sinks", function() {
-    it("returns nodes in the graph that have no out-edges", function() {
+    it("returns nodes in the graph that have no out-edges (directed graph)", function() {
       g.setPath(["a", "b", "c"]);
       g.setNode("d");
       expect(g.sinks().sort()).toEqual(["c", "d"]);
     });
+
+    it("returns nodes in the graph that have no edges (undirected graph)", function() {
+      gUndirected.setPath(["a", "b", "c", "d"]);
+      gUndirected.removeNode("c");
+      expect(_.sortBy(gUndirected.sinks())).to.eql(["d"]);
+    });
   });
 
   describe("filterNodes", function() {