diff --git a/buffet/states/state_change_queue_unittest.cc b/buffet/states/state_change_queue_unittest.cc
new file mode 100644
index 0000000..8205f77
--- /dev/null
+++ b/buffet/states/state_change_queue_unittest.cc
@@ -0,0 +1,108 @@
+// Copyright 2014 The Chromium OS 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 <gtest/gtest.h>
+
+#include "buffet/states/state_change_queue.h"
+
+namespace buffet {
+
+class StateChangeQueueTest : public ::testing::Test {
+ public:
+  void SetUp() override {
+    queue_.reset(new StateChangeQueue(100));
+  }
+
+  void TearDown() override {
+    queue_.reset();
+  }
+
+  std::unique_ptr<StateChangeQueue> queue_;
+};
+
+TEST_F(StateChangeQueueTest, Empty) {
+  EXPECT_TRUE(queue_->IsEmpty());
+  EXPECT_TRUE(queue_->GetAndClearRecordedStateChanges().empty());
+}
+
+TEST_F(StateChangeQueueTest, UpdateOne) {
+  StateChange change;
+  change.timestamp = base::Time::Now();
+  change.property_set.emplace("prop.name", int{23});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change));
+  EXPECT_FALSE(queue_->IsEmpty());
+  auto changes = queue_->GetAndClearRecordedStateChanges();
+  ASSERT_EQ(1, changes.size());
+  EXPECT_EQ(change.timestamp, changes.front().timestamp);
+  EXPECT_EQ(change.property_set, changes.front().property_set);
+  EXPECT_TRUE(queue_->IsEmpty());
+  EXPECT_TRUE(queue_->GetAndClearRecordedStateChanges().empty());
+}
+
+TEST_F(StateChangeQueueTest, UpdateMany) {
+  StateChange change1;
+  change1.timestamp = base::Time::Now();
+  change1.property_set.emplace("prop.name1", int{23});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change1));
+  StateChange change2;
+  change2.timestamp = base::Time::Now();
+  change2.property_set.emplace("prop.name1", int{17});
+  change2.property_set.emplace("prop.name2", double{1.0});
+  change2.property_set.emplace("prop.name3", bool{false});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change2));
+  EXPECT_FALSE(queue_->IsEmpty());
+  auto changes = queue_->GetAndClearRecordedStateChanges();
+  ASSERT_EQ(2, changes.size());
+  EXPECT_EQ(change1.timestamp, changes.front().timestamp);
+  EXPECT_EQ(change1.property_set, changes.front().property_set);
+  EXPECT_EQ(change2.timestamp, changes.back().timestamp);
+  EXPECT_EQ(change2.property_set, changes.back().property_set);
+  EXPECT_TRUE(queue_->IsEmpty());
+  EXPECT_TRUE(queue_->GetAndClearRecordedStateChanges().empty());
+}
+
+TEST_F(StateChangeQueueTest, MaxQueueSize) {
+  queue_.reset(new StateChangeQueue(2));
+  base::Time start_time = base::Time::Now();
+  base::TimeDelta time_delta = base::TimeDelta::FromMinutes(1);
+
+  StateChange change;
+  change.timestamp = start_time;
+  change.property_set.emplace("prop.name1", int{1});
+  change.property_set.emplace("prop.name2", int{2});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change));
+
+  change.timestamp += time_delta;
+  change.property_set.clear();
+  change.property_set.emplace("prop.name1", int{3});
+  change.property_set.emplace("prop.name3", int{4});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change));
+
+  change.timestamp += time_delta;
+  change.property_set.clear();
+  change.property_set.emplace("prop.name10", int{10});
+  change.property_set.emplace("prop.name11", int{11});
+  ASSERT_TRUE(queue_->NotifyPropertiesUpdated(change));
+
+  auto changes = queue_->GetAndClearRecordedStateChanges();
+  ASSERT_EQ(2, changes.size());
+
+  chromeos::VariantDictionary expected1{
+    {"prop.name1", int{3}},
+    {"prop.name2", int{2}},
+    {"prop.name3", int{4}},
+  };
+  EXPECT_EQ(start_time + time_delta, changes.front().timestamp);
+  EXPECT_EQ(expected1, changes.front().property_set);
+
+  chromeos::VariantDictionary expected2{
+    {"prop.name10", int{10}},
+    {"prop.name11", int{11}},
+  };
+  EXPECT_EQ(start_time + 2 * time_delta, changes.back().timestamp);
+  EXPECT_EQ(expected2, changes.back().property_set);
+}
+
+}  // namespace buffet