--- a/toolkit/components/url-classifier/tests/gtest/TestChunkSet.cpp
+++ b/toolkit/components/url-classifier/tests/gtest/TestChunkSet.cpp
@@ -1,15 +1,16 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <set>
 
 #include "gtest/gtest.h"
 #include "ChunkSet.h"
 #include "mozilla/ArrayUtils.h"
 
 TEST(UrlClassifierChunkSet, Empty)
 {
   mozilla::safebrowsing::ChunkSet chunkSet;
@@ -84,16 +85,139 @@ TEST(UrlClassifierChunkSet, Merge)
 
   ASSERT_FALSE(chunkSet.Has(11));
   ASSERT_FALSE(chunkSet.Has(15));
   ASSERT_FALSE(chunkSet.Has(17));
   ASSERT_FALSE(chunkSet.Has(18));
   ASSERT_FALSE(chunkSet.Has(19));
 }
 
+TEST(UrlClassifierChunkSet, Merge2)
+{
+  static int testVals[] = {2, 1, 5, 6, 8, 7, 14, 10, 12, 13};
+  static int mergeVals[] = {9, 3, 4, 20, 14, 16};
+  static int mergeVals2[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
+
+  mozilla::safebrowsing::ChunkSet chunkSet;
+  mozilla::safebrowsing::ChunkSet mergeSet;
+  mozilla::safebrowsing::ChunkSet mergeSet2;
+
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(testVals); i++) {
+    chunkSet.Set(testVals[i]);
+  }
+
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(mergeVals); i++) {
+    mergeSet.Set(mergeVals[i]);
+  }
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(mergeVals2); i++) {
+    mergeSet2.Set(mergeVals2[i]);
+  }
+
+  chunkSet.Merge(mergeSet);
+  chunkSet.Merge(mergeSet2);
+
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(testVals); i++) {
+    ASSERT_TRUE(chunkSet.Has(testVals[i]));
+  }
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(mergeVals); i++) {
+    ASSERT_TRUE(chunkSet.Has(mergeVals[i]));
+  }
+  for (size_t i = 0; i < MOZ_ARRAY_LENGTH(mergeVals2); i++) {
+    ASSERT_TRUE(chunkSet.Has(mergeVals2[i]));
+  }
+
+  ASSERT_FALSE(chunkSet.Has(15));
+  ASSERT_FALSE(chunkSet.Has(17));
+  ASSERT_FALSE(chunkSet.Has(18));
+  ASSERT_FALSE(chunkSet.Has(19));
+}
+
+TEST(UrlClassifierChunkSet, Stress)
+{
+  mozilla::safebrowsing::ChunkSet chunkSet;
+  mozilla::safebrowsing::ChunkSet mergeSet;
+  std::set<int> refSet;
+  std::set<int> refMergeSet;
+  static const int TEST_ITERS   =  7000;
+  static const int REMOVE_ITERS =  3000;
+  static const int TEST_RANGE   = 10000;
+
+  // Construction by Set
+  for (int i = 0; i < TEST_ITERS; i++) {
+    int chunk = rand() % TEST_RANGE;
+    chunkSet.Set(chunk);
+    refSet.insert(chunk);
+  }
+
+  // Same elements as reference set
+  for (auto it = refSet.begin(); it != refSet.end(); ++it) {
+    ASSERT_TRUE(chunkSet.Has(*it));
+  }
+
+  // Hole punching via Remove
+  for (int i = 0; i < REMOVE_ITERS; i++) {
+    int chunk = rand() % TEST_RANGE;
+    mozilla::safebrowsing::ChunkSet helpChunk;
+    helpChunk.Set(chunk);
+
+    chunkSet.Remove(helpChunk);
+    refSet.erase(chunk);
+
+    ASSERT_FALSE(chunkSet.Has(chunk));
+  }
+
+  // Should have chunks present in reference set
+  // Should not have chunks absent in reference set
+  for (int it = 0; it < TEST_RANGE; ++it) {
+    auto found = refSet.find(it);
+    if (chunkSet.Has(it)) {
+      ASSERT_FALSE(found == refSet.end());
+    } else {
+      ASSERT_TRUE(found == refSet.end());
+    }
+  }
+
+  // Construct set to merge with
+  for (int i = 0; i < TEST_ITERS; i++) {
+    int chunk = rand() % TEST_RANGE;
+    mergeSet.Set(chunk);
+    refMergeSet.insert(chunk);
+  }
+
+  // Merge set constructed correctly
+  for (auto it = refMergeSet.begin(); it != refMergeSet.end(); ++it) {
+    ASSERT_TRUE(mergeSet.Has(*it));
+  }
+
+  mozilla::safebrowsing::ChunkSet origSet;
+  origSet = chunkSet;
+
+  chunkSet.Merge(mergeSet);
+  refSet.insert(refMergeSet.begin(), refMergeSet.end());
+
+  // Check for presence of elements from both source
+  // Should not have chunks absent in reference set
+  for (int it = 0; it < TEST_RANGE; ++it) {
+    auto found = refSet.find(it);
+    if (chunkSet.Has(it)) {
+      ASSERT_FALSE(found == refSet.end());
+    } else {
+      ASSERT_TRUE(found == refSet.end());
+    }
+  }
+
+  // Unmerge
+  chunkSet.Remove(origSet);
+  for (int it = 0; it < TEST_RANGE; ++it) {
+    if (origSet.Has(it)) {
+      ASSERT_FALSE(chunkSet.Has(it));
+    }
+  }
+}
+
 TEST(UrlClassifierChunkSet, RemoveClear)
 {
   static int testVals[] = {2, 1, 5, 6, 8, 7, 14, 10, 12, 13};
   static int mergeVals[] = {3, 4, 9, 16, 20};
 
   mozilla::safebrowsing::ChunkSet chunkSet;
   mozilla::safebrowsing::ChunkSet mergeSet;
   mozilla::safebrowsing::ChunkSet removeSet;