--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/unittests/ADT/DepthFirstIteratorTest.cpp	Fri Nov 25 19:14:25 2016 +0900
@@ -0,0 +1,54 @@
+//=== llvm/unittest/ADT/DepthFirstIteratorTest.cpp - DFS iterator tests ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestGraph.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace llvm {
+
+template <typename T> struct CountedSet {
+  typedef typename SmallPtrSet<T, 4>::iterator iterator;
+
+  SmallPtrSet<T, 4> S;
+  int InsertVisited = 0;
+
+  std::pair<iterator, bool> insert(const T &Item) {
+    InsertVisited++;
+    return S.insert(Item);
+  }
+
+  size_t count(const T &Item) const { return S.count(Item); }
+  
+  void completed(T) { }
+};
+
+template <typename T> class df_iterator_storage<CountedSet<T>, true> {
+public:
+  df_iterator_storage(CountedSet<T> &VSet) : Visited(VSet) {}
+
+  CountedSet<T> &Visited;
+};
+
+TEST(DepthFirstIteratorTest, ActuallyUpdateIterator) {
+  typedef CountedSet<Graph<3>::NodeType *> StorageT;
+  typedef df_iterator<Graph<3>, StorageT, true> DFIter;
+
+  Graph<3> G;
+  G.AddEdge(0, 1);
+  G.AddEdge(0, 2);
+  StorageT S;
+  for (auto N : make_range(DFIter::begin(G, S), DFIter::end(G, S)))
+    (void)N;
+
+  EXPECT_EQ(3, S.InsertVisited);
+}
+}