diff --git a/services/surfaceflinger/tests/Transaction_test.cpp b/services/surfaceflinger/tests/Transaction_test.cpp
index 94b33ac..be8d939 100644
--- a/services/surfaceflinger/tests/Transaction_test.cpp
+++ b/services/surfaceflinger/tests/Transaction_test.cpp
@@ -15,9 +15,12 @@
  */
 
 #include <algorithm>
+#include <chrono>
+#include <cinttypes>
 #include <functional>
 #include <limits>
 #include <ostream>
+#include <thread>
 
 #include <gtest/gtest.h>
 
@@ -64,6 +67,7 @@
 const Color Color::TRANSPARENT{0, 0, 0, 0};
 
 using android::hardware::graphics::common::V1_1::BufferUsage;
+using namespace std::chrono_literals;
 
 std::ostream& operator<<(std::ostream& os, const Color& color) {
     os << int(color.r) << ", " << int(color.g) << ", " << int(color.b) << ", " << int(color.a);
@@ -327,10 +331,11 @@
         mClient = 0;
     }
 
-    virtual sp<SurfaceControl> createLayer(const char* name, uint32_t width, uint32_t height,
+    virtual sp<SurfaceControl> createLayer(const sp<SurfaceComposerClient>& client,
+                                           const char* name, uint32_t width, uint32_t height,
                                            uint32_t flags = 0) {
         auto layer =
-                mClient->createSurface(String8(name), width, height, PIXEL_FORMAT_RGBA_8888, flags);
+                client->createSurface(String8(name), width, height, PIXEL_FORMAT_RGBA_8888, flags);
         EXPECT_NE(nullptr, layer.get()) << "failed to create SurfaceControl";
 
         status_t error = Transaction()
@@ -345,6 +350,11 @@
         return layer;
     }
 
+    virtual sp<SurfaceControl> createLayer(const char* name, uint32_t width, uint32_t height,
+                                           uint32_t flags = 0) {
+        return createLayer(mClient, name, width, height, flags);
+    }
+
     ANativeWindow_Buffer getBufferQueueLayerBuffer(const sp<SurfaceControl>& layer) {
         // wait for previous transactions (such as setSize) to complete
         Transaction().apply(true);
@@ -1953,7 +1963,7 @@
                               "test");
     fillGraphicBufferColor(buffer, Rect(0, 0, 32, 32), Color::RED);
 
-    sp<Fence> fence = new Fence(-1);
+    sp<Fence> fence = Fence::NO_FENCE;
 
     Transaction()
             .setBuffer(layer, buffer)
@@ -2156,6 +2166,627 @@
     }
 }
 
+class ExpectedResult {
+public:
+    enum Transaction {
+        NOT_PRESENTED = 0,
+        PRESENTED,
+    };
+
+    enum Buffer {
+        NOT_ACQUIRED = 0,
+        ACQUIRED,
+    };
+
+    enum PreviousBuffer {
+        NOT_RELEASED = 0,
+        RELEASED,
+    };
+
+    void reset() {
+        mTransactionResult = ExpectedResult::Transaction::NOT_PRESENTED;
+        mExpectedSurfaceResults.clear();
+    }
+
+    void addSurface(ExpectedResult::Transaction transactionResult, const sp<SurfaceControl>& layer,
+                    ExpectedResult::Buffer bufferResult = NOT_ACQUIRED,
+                    ExpectedResult::PreviousBuffer previousBufferResult = NOT_RELEASED) {
+        mTransactionResult = transactionResult;
+        mExpectedSurfaceResults.emplace(std::piecewise_construct,
+                                        std::forward_as_tuple(layer->getHandle()),
+                                        std::forward_as_tuple(bufferResult, previousBufferResult));
+    }
+
+    void addSurfaces(ExpectedResult::Transaction transactionResult,
+                     const std::vector<sp<SurfaceControl>>& layers,
+                     ExpectedResult::Buffer bufferResult = NOT_ACQUIRED,
+                     ExpectedResult::PreviousBuffer previousBufferResult = NOT_RELEASED) {
+        for (const auto& layer : layers) {
+            addSurface(transactionResult, layer, bufferResult, previousBufferResult);
+        }
+    }
+
+    void verifyTransactionStats(const TransactionStats& transactionStats) const {
+        const auto& [latchTime, presentTime, surfaceStats] = transactionStats;
+        if (mTransactionResult == ExpectedResult::Transaction::PRESENTED) {
+            ASSERT_GE(latchTime, 0) << "bad latch time";
+            ASSERT_GE(presentTime, 0) << "bad present time";
+        } else {
+            ASSERT_EQ(presentTime, -1) << "transaction shouldn't have been presented";
+            ASSERT_EQ(latchTime, -1) << "unpresented transactions shouldn't be latched";
+        }
+
+        ASSERT_EQ(surfaceStats.size(), mExpectedSurfaceResults.size())
+                << "wrong number of surfaces";
+
+        for (const auto& stats : surfaceStats) {
+            const auto& expectedSurfaceResult = mExpectedSurfaceResults.find(stats.surfaceControl);
+            ASSERT_NE(expectedSurfaceResult, mExpectedSurfaceResults.end())
+                    << "unexpected surface control";
+            expectedSurfaceResult->second.verifySurfaceStats(stats, latchTime);
+        }
+    }
+
+private:
+    class ExpectedSurfaceResult {
+    public:
+        ExpectedSurfaceResult(ExpectedResult::Buffer bufferResult,
+                              ExpectedResult::PreviousBuffer previousBufferResult)
+              : mBufferResult(bufferResult), mPreviousBufferResult(previousBufferResult) {}
+
+        void verifySurfaceStats(const SurfaceStats& surfaceStats, nsecs_t latchTime) const {
+            const auto& [surfaceControl, acquireTime, releasePreviousBuffer] = surfaceStats;
+
+            ASSERT_EQ(acquireTime > 0, mBufferResult == ExpectedResult::Buffer::ACQUIRED)
+                    << "bad acquire time";
+            ASSERT_LE(acquireTime, latchTime) << "acquire time should be <= latch time";
+            ASSERT_EQ(releasePreviousBuffer,
+                      mPreviousBufferResult == ExpectedResult::PreviousBuffer::RELEASED)
+                    << "bad previous buffer released";
+        }
+
+    private:
+        ExpectedResult::Buffer mBufferResult;
+        ExpectedResult::PreviousBuffer mPreviousBufferResult;
+    };
+
+    struct IBinderHash {
+        std::size_t operator()(const sp<IBinder>& strongPointer) const {
+            return std::hash<IBinder*>{}(strongPointer.get());
+        }
+    };
+    ExpectedResult::Transaction mTransactionResult = ExpectedResult::Transaction::NOT_PRESENTED;
+    std::unordered_map<sp<IBinder>, ExpectedSurfaceResult, IBinderHash> mExpectedSurfaceResults;
+};
+
+class CallbackHelper {
+public:
+    static void function(void* callbackContext, const TransactionStats& transactionStats) {
+        if (!callbackContext) {
+            ALOGE("failed to get callback context");
+        }
+        CallbackHelper* helper = static_cast<CallbackHelper*>(callbackContext);
+        std::lock_guard lock(helper->mMutex);
+        helper->mTransactionStatsQueue.push(transactionStats);
+        helper->mConditionVariable.notify_all();
+    }
+
+    void getTransactionStats(TransactionStats* outStats) {
+        std::unique_lock lock(mMutex);
+
+        if (mTransactionStatsQueue.empty()) {
+            ASSERT_NE(mConditionVariable.wait_for(lock, std::chrono::seconds(3)),
+                      std::cv_status::timeout)
+                    << "did not receive callback";
+        }
+
+        *outStats = std::move(mTransactionStatsQueue.front());
+        mTransactionStatsQueue.pop();
+    }
+
+    void verifyFinalState() {
+        // Wait to see if there are extra callbacks
+        std::this_thread::sleep_for(500ms);
+
+        std::lock_guard lock(mMutex);
+        EXPECT_EQ(mTransactionStatsQueue.size(), 0) << "extra callbacks received";
+        mTransactionStatsQueue = {};
+    }
+
+    void* getContext() { return static_cast<void*>(this); }
+
+    std::mutex mMutex;
+    std::condition_variable mConditionVariable;
+    std::queue<TransactionStats> mTransactionStatsQueue;
+};
+
+class LayerCallbackTest : public LayerTransactionTest {
+protected:
+    virtual sp<SurfaceControl> createBufferStateLayer() {
+        return createLayer(mClient, "test", mWidth, mHeight,
+                           ISurfaceComposerClient::eFXSurfaceBufferState);
+    }
+
+    virtual void fillTransaction(Transaction& transaction, CallbackHelper* callbackHelper,
+                                 const sp<SurfaceControl>& layer = nullptr) {
+        if (layer) {
+            sp<GraphicBuffer> buffer =
+                    new GraphicBuffer(mWidth, mHeight, PIXEL_FORMAT_RGBA_8888, 1,
+                                      BufferUsage::CPU_READ_OFTEN | BufferUsage::CPU_WRITE_OFTEN |
+                                              BufferUsage::COMPOSER_OVERLAY |
+                                              BufferUsage::GPU_TEXTURE,
+                                      "test");
+            fillGraphicBufferColor(buffer, Rect(0, 0, mWidth, mHeight), Color::RED);
+
+            sp<Fence> fence = new Fence(-1);
+
+            transaction.setBuffer(layer, buffer)
+                    .setAcquireFence(layer, fence)
+                    .setSize(layer, mWidth, mHeight);
+        }
+
+        transaction.addTransactionCompletedCallback(callbackHelper->function,
+                                                    callbackHelper->getContext());
+    }
+
+    void waitForCallback(CallbackHelper& helper, const ExpectedResult& expectedResult,
+                         bool finalState = false) {
+        TransactionStats transactionStats;
+        ASSERT_NO_FATAL_FAILURE(helper.getTransactionStats(&transactionStats));
+        EXPECT_NO_FATAL_FAILURE(expectedResult.verifyTransactionStats(transactionStats));
+
+        if (finalState) {
+            ASSERT_NO_FATAL_FAILURE(helper.verifyFinalState());
+        }
+    }
+
+    void waitForCallbacks(CallbackHelper& helper,
+                          const std::vector<ExpectedResult>& expectedResults,
+                          bool finalState = false) {
+        for (const auto& expectedResult : expectedResults) {
+            waitForCallback(helper, expectedResult);
+        }
+        if (finalState) {
+            ASSERT_NO_FATAL_FAILURE(helper.verifyFinalState());
+        }
+    }
+
+    uint32_t mWidth = 32;
+    uint32_t mHeight = 32;
+};
+
+TEST_F(LayerCallbackTest, Basic) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    fillTransaction(transaction, &callback, layer);
+
+    transaction.apply();
+
+    ExpectedResult expected;
+    expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, true));
+}
+
+TEST_F(LayerCallbackTest, NoBuffer) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    fillTransaction(transaction, &callback);
+
+    transaction.setPosition(layer, mWidth, mHeight).apply();
+
+    ExpectedResult expected;
+    expected.addSurface(ExpectedResult::Transaction::NOT_PRESENTED, layer);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, true));
+}
+
+TEST_F(LayerCallbackTest, NoStateChange) {
+    Transaction transaction;
+    CallbackHelper callback;
+    fillTransaction(transaction, &callback);
+
+    transaction.apply();
+
+    ExpectedResult expected;
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, true));
+}
+
+TEST_F(LayerCallbackTest, OffScreen) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    fillTransaction(transaction, &callback, layer);
+
+    transaction.setPosition(layer, -100, -100).apply();
+
+    ExpectedResult expected;
+    expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, true));
+}
+
+TEST_F(LayerCallbackTest, Merge) {
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createBufferStateLayer());
+    ASSERT_NO_FATAL_FAILURE(layer2 = createBufferStateLayer());
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    fillTransaction(transaction1, &callback1, layer1);
+    fillTransaction(transaction2, &callback2, layer2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, Merge_SameCallback) {
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createBufferStateLayer());
+    ASSERT_NO_FATAL_FAILURE(layer2 = createBufferStateLayer());
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback;
+    fillTransaction(transaction1, &callback, layer1);
+    fillTransaction(transaction2, &callback, layer2);
+
+    transaction2.merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, true));
+}
+
+TEST_F(LayerCallbackTest, Merge_SameLayer) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    fillTransaction(transaction1, &callback1, layer);
+    fillTransaction(transaction2, &callback2, layer);
+
+    transaction2.merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, Merge_SingleBuffer) {
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createBufferStateLayer());
+    ASSERT_NO_FATAL_FAILURE(layer2 = createBufferStateLayer());
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    fillTransaction(transaction1, &callback1, layer1);
+    fillTransaction(transaction2, &callback2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, Merge_DifferentClients) {
+    sp<SurfaceComposerClient> client1(new SurfaceComposerClient),
+            client2(new SurfaceComposerClient);
+
+    ASSERT_EQ(NO_ERROR, client1->initCheck()) << "failed to create SurfaceComposerClient";
+    ASSERT_EQ(NO_ERROR, client2->initCheck()) << "failed to create SurfaceComposerClient";
+
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createLayer(client1, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+    ASSERT_NO_FATAL_FAILURE(layer2 = createLayer(client2, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    fillTransaction(transaction1, &callback1, layer1);
+    fillTransaction(transaction2, &callback2, layer2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    for (size_t i = 0; i < 10; i++) {
+        fillTransaction(transaction, &callback, layer);
+
+        transaction.apply();
+
+        ExpectedResult expected;
+        expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer,
+                            ExpectedResult::Buffer::NOT_ACQUIRED,
+                            (i == 0) ? ExpectedResult::PreviousBuffer::NOT_RELEASED
+                                     : ExpectedResult::PreviousBuffer::RELEASED);
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected));
+    }
+    ASSERT_NO_FATAL_FAILURE(callback.verifyFinalState());
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_NoStateChange) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    for (size_t i = 0; i < 10; i++) {
+        ExpectedResult expected;
+
+        if (i == 0) {
+            fillTransaction(transaction, &callback, layer);
+            expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+        } else {
+            fillTransaction(transaction, &callback);
+        }
+
+        transaction.apply();
+
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected));
+    }
+    ASSERT_NO_FATAL_FAILURE(callback.verifyFinalState());
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_SameStateChange) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    for (size_t i = 0; i < 10; i++) {
+        if (i == 0) {
+            fillTransaction(transaction, &callback, layer);
+        } else {
+            fillTransaction(transaction, &callback);
+        }
+
+        transaction.setPosition(layer, mWidth, mHeight).apply();
+
+        ExpectedResult expected;
+        expected.addSurface((i == 0) ? ExpectedResult::Transaction::PRESENTED
+                                     : ExpectedResult::Transaction::NOT_PRESENTED,
+                            layer);
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expected, i == 0));
+    }
+    ASSERT_NO_FATAL_FAILURE(callback.verifyFinalState());
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_Merge) {
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createBufferStateLayer());
+    ASSERT_NO_FATAL_FAILURE(layer2 = createBufferStateLayer());
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    for (size_t i = 0; i < 10; i++) {
+        fillTransaction(transaction1, &callback1, layer1);
+        fillTransaction(transaction2, &callback2, layer2);
+
+        transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+        ExpectedResult expected;
+        expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2},
+                             ExpectedResult::Buffer::NOT_ACQUIRED,
+                             (i == 0) ? ExpectedResult::PreviousBuffer::NOT_RELEASED
+                                      : ExpectedResult::PreviousBuffer::RELEASED);
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected));
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected));
+    }
+    ASSERT_NO_FATAL_FAILURE(callback1.verifyFinalState());
+    ASSERT_NO_FATAL_FAILURE(callback2.verifyFinalState());
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_Merge_DifferentClients) {
+    sp<SurfaceComposerClient> client1(new SurfaceComposerClient),
+            client2(new SurfaceComposerClient);
+    ASSERT_EQ(NO_ERROR, client1->initCheck()) << "failed to create SurfaceComposerClient";
+    ASSERT_EQ(NO_ERROR, client2->initCheck()) << "failed to create SurfaceComposerClient";
+
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createLayer(client1, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+    ASSERT_NO_FATAL_FAILURE(layer2 = createLayer(client2, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+    for (size_t i = 0; i < 10; i++) {
+        fillTransaction(transaction1, &callback1, layer1);
+        fillTransaction(transaction2, &callback2, layer2);
+
+        transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+        ExpectedResult expected;
+        expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2},
+                             ExpectedResult::Buffer::NOT_ACQUIRED,
+                             (i == 0) ? ExpectedResult::PreviousBuffer::NOT_RELEASED
+                                      : ExpectedResult::PreviousBuffer::RELEASED);
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected));
+        EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected));
+    }
+    ASSERT_NO_FATAL_FAILURE(callback1.verifyFinalState());
+    ASSERT_NO_FATAL_FAILURE(callback2.verifyFinalState());
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_Merge_DifferentClients_NoStateChange) {
+    sp<SurfaceComposerClient> client1(new SurfaceComposerClient),
+            client2(new SurfaceComposerClient);
+    ASSERT_EQ(NO_ERROR, client1->initCheck()) << "failed to create SurfaceComposerClient";
+    ASSERT_EQ(NO_ERROR, client2->initCheck()) << "failed to create SurfaceComposerClient";
+
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createLayer(client1, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+    ASSERT_NO_FATAL_FAILURE(layer2 = createLayer(client2, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+
+    // Normal call to set up test
+    fillTransaction(transaction1, &callback1, layer1);
+    fillTransaction(transaction2, &callback2, layer2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+    expected.reset();
+
+    // Test
+    fillTransaction(transaction1, &callback1);
+    fillTransaction(transaction2, &callback2);
+
+    transaction2.merge(std::move(transaction1)).apply();
+
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_Merge_DifferentClients_SameStateChange) {
+    sp<SurfaceComposerClient> client1(new SurfaceComposerClient),
+            client2(new SurfaceComposerClient);
+
+    ASSERT_EQ(NO_ERROR, client1->initCheck()) << "failed to create SurfaceComposerClient";
+    ASSERT_EQ(NO_ERROR, client2->initCheck()) << "failed to create SurfaceComposerClient";
+
+    sp<SurfaceControl> layer1, layer2;
+    ASSERT_NO_FATAL_FAILURE(layer1 = createLayer(client1, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+    ASSERT_NO_FATAL_FAILURE(layer2 = createLayer(client2, "test", mWidth, mHeight,
+                                                 ISurfaceComposerClient::eFXSurfaceBufferState));
+
+    Transaction transaction1, transaction2;
+    CallbackHelper callback1, callback2;
+
+    // Normal call to set up test
+    fillTransaction(transaction1, &callback1, layer1);
+    fillTransaction(transaction2, &callback2, layer2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    ExpectedResult expected;
+    expected.addSurfaces(ExpectedResult::Transaction::PRESENTED, {layer1, layer2});
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+    expected.reset();
+
+    // Test
+    fillTransaction(transaction1, &callback1);
+    fillTransaction(transaction2, &callback2);
+
+    transaction2.setPosition(layer2, mWidth, mHeight).merge(std::move(transaction1)).apply();
+
+    expected.addSurface(ExpectedResult::Transaction::NOT_PRESENTED, layer2);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback1, expected, true));
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback2, expected, true));
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_SingleFrame) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    std::vector<ExpectedResult> expectedResults(50);
+    ExpectedResult::PreviousBuffer previousBufferResult =
+            ExpectedResult::PreviousBuffer::NOT_RELEASED;
+    for (auto& expected : expectedResults) {
+        expected.reset();
+        expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer,
+                            ExpectedResult::Buffer::NOT_ACQUIRED, previousBufferResult);
+        previousBufferResult = ExpectedResult::PreviousBuffer::RELEASED;
+
+        fillTransaction(transaction, &callback, layer);
+
+        transaction.apply();
+        std::this_thread::sleep_for(200ms);
+    }
+    EXPECT_NO_FATAL_FAILURE(waitForCallbacks(callback, expectedResults, true));
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_SingleFrame_NoStateChange) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    Transaction transaction;
+    CallbackHelper callback;
+    std::vector<ExpectedResult> expectedResults(50);
+    bool first = true;
+    for (auto& expected : expectedResults) {
+        expected.reset();
+
+        if (first) {
+            fillTransaction(transaction, &callback, layer);
+            expected.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+            first = false;
+        } else {
+            fillTransaction(transaction, &callback);
+        }
+
+        transaction.apply();
+        std::this_thread::sleep_for(200ms);
+    }
+    EXPECT_NO_FATAL_FAILURE(waitForCallbacks(callback, expectedResults, true));
+}
+
+TEST_F(LayerCallbackTest, MultipleTransactions_SingleFrame_SameStateChange) {
+    sp<SurfaceControl> layer;
+    ASSERT_NO_FATAL_FAILURE(layer = createBufferStateLayer());
+
+    // Normal call to set up test
+    Transaction transaction;
+    CallbackHelper callback;
+    fillTransaction(transaction, &callback, layer);
+
+    transaction.setPosition(layer, mWidth, mHeight).apply();
+
+    ExpectedResult expectedResult;
+    expectedResult.addSurface(ExpectedResult::Transaction::PRESENTED, layer);
+    EXPECT_NO_FATAL_FAILURE(waitForCallback(callback, expectedResult, true));
+
+    // Test
+    std::vector<ExpectedResult> expectedResults(50);
+    for (auto& expected : expectedResults) {
+        expected.reset();
+        expected.addSurface(ExpectedResult::Transaction::NOT_PRESENTED, layer);
+
+        fillTransaction(transaction, &callback);
+
+        transaction.setPosition(layer, mWidth, mHeight).apply();
+
+        std::this_thread::sleep_for(200ms);
+    }
+    EXPECT_NO_FATAL_FAILURE(waitForCallbacks(callback, expectedResults, true));
+}
+
 class LayerUpdateTest : public LayerTransactionTest {
 protected:
     virtual void SetUp() {