diff --git a/test/unittests/heap/memory-reducer-unittest.cc b/test/unittests/heap/memory-reducer-unittest.cc
index 1088f01..4787bc6 100644
--- a/test/unittests/heap/memory-reducer-unittest.cc
+++ b/test/unittests/heap/memory-reducer-unittest.cc
@@ -74,10 +74,9 @@
   return TimerEvent(time_ms, true, false);
 }
 
-
-MemoryReducer::Event ContextDisposedEvent(double time_ms) {
+MemoryReducer::Event PossibleGarbageEvent(double time_ms) {
   MemoryReducer::Event event;
-  event.type = MemoryReducer::kContextDisposed;
+  event.type = MemoryReducer::kPossibleGarbage;
   event.time_ms = time_ms;
   return event;
 }
@@ -114,7 +113,7 @@
   EXPECT_EQ(0, state1.started_gcs);
   EXPECT_EQ(2, state1.last_gc_time_ms);
 
-  state1 = MemoryReducer::Step(state0, ContextDisposedEvent(0));
+  state1 = MemoryReducer::Step(state0, PossibleGarbageEvent(0));
   EXPECT_EQ(MemoryReducer::kWait, state1.action);
   EXPECT_EQ(MemoryReducer::kLongDelayMs, state1.next_gc_start_ms);
   EXPECT_EQ(0, state1.started_gcs);
@@ -127,7 +126,7 @@
 
   MemoryReducer::State state0(WaitState(2, 1000.0)), state1(DoneState());
 
-  state1 = MemoryReducer::Step(state0, ContextDisposedEvent(2000));
+  state1 = MemoryReducer::Step(state0, PossibleGarbageEvent(2000));
   EXPECT_EQ(MemoryReducer::kWait, state1.action);
   EXPECT_EQ(state0.next_gc_start_ms, state1.next_gc_start_ms);
   EXPECT_EQ(state0.started_gcs, state1.started_gcs);
@@ -250,7 +249,7 @@
   EXPECT_EQ(state0.started_gcs, state1.started_gcs);
   EXPECT_EQ(state0.last_gc_time_ms, state1.last_gc_time_ms);
 
-  state1 = MemoryReducer::Step(state0, ContextDisposedEvent(2000));
+  state1 = MemoryReducer::Step(state0, PossibleGarbageEvent(2000));
   EXPECT_EQ(MemoryReducer::kRun, state1.action);
   EXPECT_EQ(state0.next_gc_start_ms, state1.next_gc_start_ms);
   EXPECT_EQ(state0.started_gcs, state1.started_gcs);
diff --git a/test/unittests/heap/slot-set-unittest.cc b/test/unittests/heap/slot-set-unittest.cc
new file mode 100644
index 0000000..3761889
--- /dev/null
+++ b/test/unittests/heap/slot-set-unittest.cc
@@ -0,0 +1,143 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <limits>
+
+#include "src/globals.h"
+#include "src/heap/slot-set.h"
+#include "src/heap/spaces.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace v8 {
+namespace internal {
+
+TEST(SlotSet, InsertAndLookup1) {
+  SlotSet set;
+  set.SetPageStart(0);
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    EXPECT_FALSE(set.Lookup(i));
+  }
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    set.Insert(i);
+  }
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    EXPECT_TRUE(set.Lookup(i));
+  }
+}
+
+TEST(SlotSet, InsertAndLookup2) {
+  SlotSet set;
+  set.SetPageStart(0);
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 7 == 0) {
+      set.Insert(i);
+    }
+  }
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 7 == 0) {
+      EXPECT_TRUE(set.Lookup(i));
+    } else {
+      EXPECT_FALSE(set.Lookup(i));
+    }
+  }
+}
+
+TEST(SlotSet, Iterate) {
+  SlotSet set;
+  set.SetPageStart(0);
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 7 == 0) {
+      set.Insert(i);
+    }
+  }
+
+  set.Iterate([](Address slot_address) {
+    uintptr_t intaddr = reinterpret_cast<uintptr_t>(slot_address);
+    if (intaddr % 3 == 0) {
+      return SlotSet::KEEP_SLOT;
+    } else {
+      return SlotSet::REMOVE_SLOT;
+    }
+  });
+
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 21 == 0) {
+      EXPECT_TRUE(set.Lookup(i));
+    } else {
+      EXPECT_FALSE(set.Lookup(i));
+    }
+  }
+}
+
+TEST(SlotSet, Remove) {
+  SlotSet set;
+  set.SetPageStart(0);
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 7 == 0) {
+      set.Insert(i);
+    }
+  }
+
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 3 != 0) {
+      set.Remove(i);
+    }
+  }
+
+  for (int i = 0; i < Page::kPageSize; i += kPointerSize) {
+    if (i % 21 == 0) {
+      EXPECT_TRUE(set.Lookup(i));
+    } else {
+      EXPECT_FALSE(set.Lookup(i));
+    }
+  }
+}
+
+void CheckRemoveRangeOn(uint32_t start, uint32_t end) {
+  SlotSet set;
+  set.SetPageStart(0);
+  uint32_t first = start == 0 ? 0 : start - kPointerSize;
+  uint32_t last = end == Page::kPageSize ? end - kPointerSize : end;
+  for (uint32_t i = first; i <= last; i += kPointerSize) {
+    set.Insert(i);
+  }
+  set.RemoveRange(start, end);
+  if (first != start) {
+    EXPECT_TRUE(set.Lookup(first));
+  }
+  if (last == end) {
+    EXPECT_TRUE(set.Lookup(last));
+  }
+  for (uint32_t i = start; i < end; i += kPointerSize) {
+    EXPECT_FALSE(set.Lookup(i));
+  }
+}
+
+TEST(SlotSet, RemoveRange) {
+  CheckRemoveRangeOn(0, Page::kPageSize);
+  CheckRemoveRangeOn(1 * kPointerSize, 1023 * kPointerSize);
+  for (uint32_t start = 0; start <= 32; start++) {
+    CheckRemoveRangeOn(start * kPointerSize, (start + 1) * kPointerSize);
+    CheckRemoveRangeOn(start * kPointerSize, (start + 2) * kPointerSize);
+    const uint32_t kEnds[] = {32, 64, 100, 128, 1024, 1500, 2048};
+    for (int i = 0; i < sizeof(kEnds) / sizeof(uint32_t); i++) {
+      for (int k = -3; k <= 3; k++) {
+        uint32_t end = (kEnds[i] + k);
+        if (start < end) {
+          CheckRemoveRangeOn(start * kPointerSize, end * kPointerSize);
+        }
+      }
+    }
+  }
+  SlotSet set;
+  set.SetPageStart(0);
+  set.Insert(Page::kPageSize / 2);
+  set.RemoveRange(0, Page::kPageSize);
+  for (uint32_t i = 0; i < Page::kPageSize; i += kPointerSize) {
+    EXPECT_FALSE(set.Lookup(i));
+  }
+}
+
+}  // namespace internal
+}  // namespace v8