diff --git a/services/surfaceflinger/Android.bp b/services/surfaceflinger/Android.bp
index cc93105..4775e4e 100644
--- a/services/surfaceflinger/Android.bp
+++ b/services/surfaceflinger/Android.bp
@@ -2,3 +2,5 @@
     name: "libsurfaceflingerincludes",
     export_include_dirs: ["."],
 }
+
+subdirs = ["tests/fakehwc"]
\ No newline at end of file
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
index e34fa16..704b17e 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.cpp
@@ -157,15 +157,11 @@
     write64(metadata.usage);
 }
 
-Composer::Composer(bool useVrComposer)
+Composer::Composer(const std::string& serviceName)
     : mWriter(kWriterInitialSize),
-      mIsUsingVrComposer(useVrComposer)
+      mIsUsingVrComposer(serviceName == std::string("vr"))
 {
-    if (mIsUsingVrComposer) {
-        mComposer = IComposer::getService("vr");
-    } else {
-        mComposer = IComposer::getService(); // use default name
-    }
+    mComposer = IComposer::getService(serviceName);
 
     if (mComposer == nullptr) {
         LOG_ALWAYS_FATAL("failed to get hwcomposer service");
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.h b/services/surfaceflinger/DisplayHardware/ComposerHal.h
index 96dd833..40d2a4c 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.h
@@ -136,7 +136,7 @@
 // Composer is a wrapper to IComposer, a proxy to server-side composer.
 class Composer {
 public:
-    Composer(bool useVrComposer);
+    Composer(const std::string& serviceName);
 
     std::vector<IComposer::Capability> getCapabilities();
     std::string dumpDebugInfo();
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.cpp b/services/surfaceflinger/DisplayHardware/HWC2.cpp
index 270a732..b749ce6 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWC2.cpp
@@ -88,8 +88,8 @@
 
 // Device methods
 
-Device::Device(bool useVrComposer)
-  : mComposer(std::make_unique<Hwc2::Composer>(useVrComposer)),
+Device::Device(const std::string& serviceName)
+  : mComposer(std::make_unique<Hwc2::Composer>(serviceName)),
     mCapabilities(),
     mDisplays(),
     mHotplug(),
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.h b/services/surfaceflinger/DisplayHardware/HWC2.h
index 404bb28..9bcda1e 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2.h
@@ -63,10 +63,9 @@
 class Device
 {
 public:
-    // useVrComposer is passed to the composer HAL. When true, the composer HAL
-    // will use the vr composer service, otherwise it uses the real hardware
-    // composer.
-    Device(bool useVrComposer);
+    // Service name is expected to be 'default' or 'vr' for normal use.
+    // 'vr' will slightly modify the behavior of the mComposer.
+    Device(const std::string& serviceName);
     ~Device();
 
     friend class HWC2::Display;
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index ac2dde2..abf7dd1 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -59,7 +59,7 @@
 
 // ---------------------------------------------------------------------------
 
-HWComposer::HWComposer(bool useVrComposer)
+HWComposer::HWComposer(const std::string& serviceName)
     : mHwcDevice(),
       mDisplayData(2),
       mFreeDisplaySlots(),
@@ -74,7 +74,7 @@
         mVSyncCounts[i] = 0;
     }
 
-    loadHwcModule(useVrComposer);
+    loadHwcModule(serviceName);
 }
 
 HWComposer::~HWComposer() {}
@@ -103,10 +103,11 @@
 }
 
 // Load and prepare the hardware composer module.  Sets mHwc.
-void HWComposer::loadHwcModule(bool useVrComposer)
+void HWComposer::loadHwcModule(const std::string& serviceName)
 {
     ALOGV("loadHwcModule");
-    mHwcDevice = std::make_unique<HWC2::Device>(useVrComposer);
+    mHwcDevice = std::make_unique<HWC2::Device>(serviceName);
+
     mRemainingHwcVirtualDisplays = mHwcDevice->getMaxVirtualDisplayCount();
 }
 
diff --git a/services/surfaceflinger/DisplayHardware/HWComposer.h b/services/surfaceflinger/DisplayHardware/HWComposer.h
index 7463362..3dfb65b 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.h
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.h
@@ -75,10 +75,9 @@
         virtual ~EventHandler() {}
     };
 
-    // useVrComposer is passed to the composer HAL. When true, the composer HAL
-    // will use the vr composer service, otherwise it uses the real hardware
-    // composer.
-    HWComposer(bool useVrComposer);
+    // Uses the named composer service. Valid choices for normal use
+    // are 'default' and 'vr'.
+    HWComposer(const std::string& serviceName);
 
     ~HWComposer();
 
@@ -170,7 +169,7 @@
 private:
     static const int32_t VIRTUAL_DISPLAY_ID_BASE = 2;
 
-    void loadHwcModule(bool useVrComposer);
+    void loadHwcModule(const std::string& serviceName);
 
     bool isValidDisplay(int32_t displayId) const;
     static void validateChange(HWC2::Composition from, HWC2::Composition to);
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 8eb4067..3903a55 100755
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -40,6 +40,7 @@
 
 #include <gui/BufferItem.h>
 #include <gui/BufferQueue.h>
+#include <gui/LayerDebugInfo.h>
 #include <gui/Surface.h>
 
 #include "clz.h"
@@ -2363,71 +2364,51 @@
 // debugging
 // ----------------------------------------------------------------------------
 
-void Layer::dump(String8& result, Colorizer& colorizer) const
-{
-    const Layer::State& s(getDrawingState());
-
-    colorizer.colorize(result, Colorizer::GREEN);
-    result.appendFormat(
-            "+ %s %p (%s)\n",
-            getTypeId(), this, getName().string());
-    colorizer.reset(result);
-
-    s.activeTransparentRegion.dump(result, "transparentRegion");
-    visibleRegion.dump(result, "visibleRegion");
-    surfaceDamageRegion.dump(result, "surfaceDamageRegion");
-    sp<Client> client(mClientRef.promote());
-    PixelFormat pf = PIXEL_FORMAT_UNKNOWN;
-    const sp<GraphicBuffer>& buffer(getActiveBuffer());
-    if (buffer != NULL) {
-        pf = buffer->getPixelFormat();
-    }
-
+LayerDebugInfo Layer::getLayerDebugInfo() const {
+    LayerDebugInfo info;
+    const Layer::State& ds = getDrawingState();
+    info.mName = getName();
     sp<Layer> parent = getParent();
-
-    result.appendFormat(            "      "
-            "layerStack=%4d, z=%9d, pos=(%g,%g), size=(%4d,%4d), "
-            "crop=(%4d,%4d,%4d,%4d), finalCrop=(%4d,%4d,%4d,%4d), "
-            "isOpaque=%1d, invalidate=%1d, "
-            "dataspace=%s, pixelformat=%s "
-#ifdef USE_HWC2
-            "alpha=%.3f, flags=0x%08x, tr=[%.2f, %.2f][%.2f, %.2f]\n"
-#else
-            "alpha=0x%02x, flags=0x%08x, tr=[%.2f, %.2f][%.2f, %.2f]\n"
-#endif
-            "      client=%p parent=%s\n",
-            getLayerStack(), s.z,
-            s.active.transform.tx(), s.active.transform.ty(),
-            s.active.w, s.active.h,
-            s.crop.left, s.crop.top,
-            s.crop.right, s.crop.bottom,
-            s.finalCrop.left, s.finalCrop.top,
-            s.finalCrop.right, s.finalCrop.bottom,
-            isOpaque(s), contentDirty,
-            dataspaceDetails(getDataSpace()).c_str(), decodePixelFormat(pf).c_str(),
-            s.alpha, s.flags,
-            s.active.transform[0][0], s.active.transform[0][1],
-            s.active.transform[1][0], s.active.transform[1][1],
-            client.get(), parent == nullptr ? "none" : parent->getName().string());
-
-    sp<const GraphicBuffer> buf0(mActiveBuffer);
-    uint32_t w0=0, h0=0, s0=0, f0=0;
-    if (buf0 != 0) {
-        w0 = buf0->getWidth();
-        h0 = buf0->getHeight();
-        s0 = buf0->getStride();
-        f0 = buf0->format;
+    info.mParentName = (parent == nullptr ? std::string("none") : parent->getName().string());
+    info.mType = String8(getTypeId());
+    info.mTransparentRegion = ds.activeTransparentRegion;
+    info.mVisibleRegion = visibleRegion;
+    info.mSurfaceDamageRegion = surfaceDamageRegion;
+    info.mLayerStack = getLayerStack();
+    info.mX = ds.active.transform.tx();
+    info.mY = ds.active.transform.ty();
+    info.mZ = ds.z;
+    info.mWidth = ds.active.w;
+    info.mHeight = ds.active.h;
+    info.mCrop = ds.crop;
+    info.mFinalCrop = ds.finalCrop;
+    info.mAlpha = ds.alpha;
+    info.mFlags = ds.flags;
+    info.mPixelFormat = getPixelFormat();
+    info.mDataSpace = getDataSpace();
+    info.mMatrix[0][0] = ds.active.transform[0][0];
+    info.mMatrix[0][1] = ds.active.transform[0][1];
+    info.mMatrix[1][0] = ds.active.transform[1][0];
+    info.mMatrix[1][1] = ds.active.transform[1][1];
+    {
+        sp<const GraphicBuffer> activeBuffer = getActiveBuffer();
+        if (activeBuffer != 0) {
+            info.mActiveBufferWidth = activeBuffer->getWidth();
+            info.mActiveBufferHeight = activeBuffer->getHeight();
+            info.mActiveBufferStride = activeBuffer->getStride();
+            info.mActiveBufferFormat = activeBuffer->format;
+        } else {
+            info.mActiveBufferWidth = 0;
+            info.mActiveBufferHeight = 0;
+            info.mActiveBufferStride = 0;
+            info.mActiveBufferFormat = 0;
+        }
     }
-    result.appendFormat(
-            "      "
-            "format=%2d, activeBuffer=[%4ux%4u:%4u,%3X],"
-            " queued-frames=%d, mRefreshPending=%d\n",
-            mFormat, w0, h0, s0,f0,
-            mQueuedFrames, mRefreshPending);
-
-    if (mSurfaceFlingerConsumer != 0) {
-        mSurfaceFlingerConsumer->dumpState(result, "            ");
-    }
+    info.mNumQueuedFrames = getQueuedFrameCount();
+    info.mRefreshPending = isBufferLatched();
+    info.mIsOpaque = isOpaque(ds);
+    info.mContentDirty = contentDirty;
+    return info;
 }
 
 #ifdef USE_HWC2
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 2306d1a..8df8c49 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -60,6 +60,7 @@
 class DisplayDevice;
 class GraphicBuffer;
 class SurfaceFlinger;
+class LayerDebugInfo;
 
 // ---------------------------------------------------------------------------
 
@@ -441,6 +442,8 @@
     bool hasQueuedFrame() const { return mQueuedFrames > 0 ||
             mSidebandStreamChanged || mAutoRefresh; }
 
+    int32_t getQueuedFrameCount() const { return mQueuedFrames; }
+
 #ifdef USE_HWC2
     // -----------------------------------------------------------------------
 
@@ -489,9 +492,9 @@
     inline  const State&    getCurrentState() const { return mCurrentState; }
     inline  State&          getCurrentState()       { return mCurrentState; }
 
+    LayerDebugInfo getLayerDebugInfo() const;
 
     /* always call base class first */
-    void dump(String8& result, Colorizer& colorizer) const;
 #ifdef USE_HWC2
     static void miniDumpHeader(String8& result);
     void miniDump(String8& result, int32_t hwcId) const;
@@ -689,6 +692,9 @@
     sp<IGraphicBufferProducer> getProducer() const;
     const String8& getName() const;
     void notifyAvailableFrames();
+
+    PixelFormat getPixelFormat() const { return mFormat; }
+
 private:
 
     // -----------------------------------------------------------------------
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index aaaafbf..4154d6a 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -46,6 +46,7 @@
 #include <gui/BufferQueue.h>
 #include <gui/GuiConfig.h>
 #include <gui/IDisplayEventConnection.h>
+#include <gui/LayerDebugInfo.h>
 #include <gui/Surface.h>
 
 #include <ui/GraphicBufferAllocator.h>
@@ -123,6 +124,21 @@
 int64_t SurfaceFlinger::maxFrameBufferAcquiredBuffers;
 bool SurfaceFlinger::hasWideColorDisplay;
 
+
+std::string getHwcServiceName() {
+    char value[PROPERTY_VALUE_MAX] = {};
+    property_get("debug.sf.hwc_service_name", value, "default");
+    ALOGI("Using HWComposer service: '%s'", value);
+    return std::string(value);
+}
+
+bool useTrebleTestingOverride() {
+    char value[PROPERTY_VALUE_MAX] = {};
+    property_get("debug.sf.treble_testing_override", value, "false");
+    ALOGI("Treble testing override: '%s'", value);
+    return std::string(value) == "true";
+}
+
 SurfaceFlinger::SurfaceFlinger()
     :   BnSurfaceComposer(),
         mTransactionFlags(0),
@@ -134,6 +150,7 @@
         mHwc(nullptr),
         mRealHwc(nullptr),
         mVrHwc(nullptr),
+        mHwcServiceName(getHwcServiceName()),
         mRenderEngine(nullptr),
         mBootTime(systemTime()),
         mBuiltinDisplays(),
@@ -233,6 +250,15 @@
     // but since /data may be encrypted, we need to wait until after vold
     // comes online to attempt to read the property. The property is
     // instead read after the boot animation
+
+    if (useTrebleTestingOverride()) {
+        // Without the override SurfaceFlinger cannot connect to HIDL
+        // services that are not listed in the manifests.  Considered
+        // deriving the setting from the set service name, but it
+        // would be brittle if the name that's not 'default' is used
+        // for production purposes later on.
+        setenv("TREBLE_TESTING_OVERRIDE", "true", true);
+    }
 }
 
 void SurfaceFlinger::onFirstRef()
@@ -594,7 +620,7 @@
     // initialize the primary display.
     LOG_ALWAYS_FATAL_IF(mVrFlingerRequestsDisplay,
         "Starting with vr flinger active is not currently supported.");
-    mRealHwc = new HWComposer(false);
+    mRealHwc = new HWComposer(mHwcServiceName);
     mHwc = mRealHwc;
     mHwc->setEventHandler(static_cast<HWComposer::EventHandler*>(this));
 
@@ -1055,6 +1081,33 @@
     return NO_ERROR;
 }
 
+status_t SurfaceFlinger::getLayerDebugInfo(std::vector<LayerDebugInfo>* outLayers) const {
+    IPCThreadState* ipc = IPCThreadState::self();
+    const int pid = ipc->getCallingPid();
+    const int uid = ipc->getCallingUid();
+    if ((uid != AID_SHELL) &&
+            !PermissionCache::checkPermission(sDump, pid, uid)) {
+        ALOGE("Layer debug info permission denied for pid=%d, uid=%d", pid, uid);
+        return PERMISSION_DENIED;
+    }
+
+    // Try to acquire a lock for 1s, fail gracefully
+    const status_t err = mStateLock.timedLock(s2ns(1));
+    const bool locked = (err == NO_ERROR);
+    if (!locked) {
+        ALOGE("LayerDebugInfo: SurfaceFlinger unresponsive (%s [%d]) - exit", strerror(-err), err);
+        return TIMED_OUT;
+    }
+
+    outLayers->clear();
+    mCurrentState.traverseInZOrder([&](Layer* layer) {
+        outLayers->push_back(layer->getLayerDebugInfo());
+    });
+
+    mStateLock.unlock();
+    return NO_ERROR;
+}
+
 // ----------------------------------------------------------------------------
 
 sp<IDisplayEventConnection> SurfaceFlinger::createDisplayEventConnection(
@@ -1312,7 +1365,7 @@
 
     if (vrFlingerRequestsDisplay && !mVrHwc) {
         // Construct new HWComposer without holding any locks.
-        mVrHwc = new HWComposer(true);
+        mVrHwc = new HWComposer("vr");
 
         // Set up the event handlers. This step is neccessary to initialize the internal state of
         // the hardware composer object properly. Our callbacks are designed such that if they are
@@ -3706,7 +3759,7 @@
     result.appendFormat("Visible layers (count = %zu)\n", mNumLayers);
     colorizer.reset(result);
     mCurrentState.traverseInZOrder([&](Layer* layer) {
-        layer->dump(result, colorizer);
+        result.append(to_string(layer->getLayerDebugInfo()).c_str());
     });
 
     /*
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index acfad46..5123b58 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -300,6 +300,7 @@
             HdrCapabilities* outCapabilities) const;
     virtual status_t enableVSyncInjections(bool enable);
     virtual status_t injectVSync(nsecs_t when);
+    virtual status_t getLayerDebugInfo(std::vector<LayerDebugInfo>* outLayers) const;
 
 
     /* ------------------------------------------------------------------------
@@ -628,6 +629,7 @@
 #ifdef USE_HWC2
     HWComposer* mRealHwc;
     HWComposer* mVrHwc;
+    const std::string mHwcServiceName; // "default" for real use, something else for testing.
 #endif
     // constant members (no synchronization needed for access)
     RenderEngine* mRenderEngine;
diff --git a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
index dae03b3..7aaa42a 100644
--- a/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
+++ b/services/surfaceflinger/SurfaceFlinger_hwc1.cpp
@@ -41,6 +41,7 @@
 #include <gui/BufferQueue.h>
 #include <gui/GuiConfig.h>
 #include <gui/IDisplayEventConnection.h>
+#include <gui/LayerDebugInfo.h>
 #include <gui/Surface.h>
 
 #include <ui/GraphicBufferAllocator.h>
@@ -931,6 +932,34 @@
     return NO_ERROR;
 }
 
+status_t SurfaceFlinger::getLayerDebugInfo(std::vector<LayerDebugInfo>* outLayers) const {
+    IPCThreadState* ipc = IPCThreadState::self();
+    const int pid = ipc->getCallingPid();
+    const int uid = ipc->getCallingUid();
+    if ((uid != AID_SHELL) &&
+            !PermissionCache::checkPermission(sDump, pid, uid)) {
+        ALOGE("Layer debug info permission denied for pid=%d, uid=%d", pid, uid);
+        return PERMISSION_DENIED;
+    }
+
+    // Try to acquire a lock for 1s, fail gracefully
+    status_t err = mStateLock.timedLock(s2ns(1));
+    bool locked = (err == NO_ERROR);
+    if (!locked) {
+        ALOGE("LayerDebugInfo: SurfaceFlinger unresponsive (%s [%d]) - exit", strerror(-err), err);
+        return TIMED_OUT;
+    }
+
+    outLayers->clear();
+    mCurrentState.traverseInZOrder([&](Layer* layer) {
+            outLayers->push_back(layer->getLayerDebugInfo());
+        });
+
+    mStateLock.unlock();
+
+    return NO_ERROR;
+}
+
 // ----------------------------------------------------------------------------
 
 sp<IDisplayEventConnection> SurfaceFlinger::createDisplayEventConnection(
@@ -3261,7 +3290,7 @@
     result.appendFormat("Visible layers (count = %zu)\n", mNumLayers);
     colorizer.reset(result);
     mCurrentState.traverseInZOrder([&](Layer* layer) {
-        layer->dump(result, colorizer);
+        result.append(to_string(layer->getLayerDebugInfo()).c_str());
     });
 
     /*
diff --git a/services/surfaceflinger/tests/fakehwc/Android.bp b/services/surfaceflinger/tests/fakehwc/Android.bp
new file mode 100644
index 0000000..94f3f25
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/Android.bp
@@ -0,0 +1,35 @@
+cc_test {
+    name: "sffakehwc_test",
+    srcs: [
+         "FakeComposerClient.cpp",
+         "FakeComposerService.cpp",
+         "FakeComposerUtils.cpp",
+         "SFFakeHwc_test.cpp"
+    ],
+    shared_libs: [
+        "libcutils",
+        "libutils",
+        "libbinder",
+        "libui",
+        "libgui",
+        "liblog",
+        "libnativewindow",
+        "android.hardware.graphics.composer@2.1",
+        "android.hardware.graphics.mapper@2.0",
+        "libhwbinder",
+        "libhardware",
+        "libhidlbase",
+        "libsync",
+        "libfmq",
+        "libbase",
+        "libhidltransport"
+    ],
+    static_libs: [
+        "libhwcomposer-client",
+        "libsurfaceflingerincludes",
+        "libtrace_proto",
+        "libgmock"
+    ],
+    tags: ["tests"],
+    test_suites: ["device-tests"]
+}
\ No newline at end of file
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerClient.cpp b/services/surfaceflinger/tests/fakehwc/FakeComposerClient.cpp
new file mode 100644
index 0000000..60916f3
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerClient.cpp
@@ -0,0 +1,613 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//#define LOG_NDEBUG 0
+#undef LOG_TAG
+#define LOG_TAG "FakeComposer"
+
+#include "FakeComposerClient.h"
+
+#include <gui/SurfaceComposerClient.h>
+
+#include <log/log.h>
+
+#include <gtest/gtest.h>
+
+#include <inttypes.h>
+#include <time.h>
+#include <algorithm>
+#include <condition_variable>
+#include <iostream>
+#include <mutex>
+#include <set>
+#include <thread>
+
+constexpr Config NULL_DISPLAY_CONFIG = static_cast<Config>(0);
+constexpr Display DEFAULT_DISPLAY = static_cast<Display>(1);
+
+using namespace sftest;
+
+using android::Condition;
+using android::Mutex;
+
+using Clock = std::chrono::steady_clock;
+using TimePoint = std::chrono::time_point<Clock>;
+
+namespace {
+
+// Internal state of a layer in the HWC API.
+class LayerImpl {
+public:
+    LayerImpl() = default;
+
+    bool mValid = true;
+    RenderState mRenderState;
+    uint32_t mZ = 0;
+};
+
+// Struct for storing per frame rectangle state. Contains the render
+// state shared to the test case. Basically a snapshot and a subset of
+// LayerImpl sufficient to re-create the pixels of a layer for the
+// frame.
+struct FrameRect {
+public:
+    FrameRect(Layer layer_, const RenderState& state, uint32_t z_)
+          : layer(layer_), renderState(state), z(z_) {}
+
+    const Layer layer;
+    const RenderState renderState;
+    const uint32_t z;
+};
+
+// Collection of FrameRects forming one rendered frame. Could store
+// related fences and other data in the future.
+class Frame {
+public:
+    Frame() = default;
+    std::vector<std::unique_ptr<FrameRect>> rectangles;
+};
+
+class DelayedEventGenerator {
+public:
+    DelayedEventGenerator(std::function<void()> onTimerExpired)
+          : mOnTimerExpired(onTimerExpired), mThread([this]() { loop(); }) {}
+
+    ~DelayedEventGenerator() {
+        ALOGI("DelayedEventGenerator exiting.");
+        {
+            std::unique_lock<std::mutex> lock(mMutex);
+            mRunning = false;
+            mWakeups.clear();
+            mCondition.notify_one();
+        }
+        mThread.join();
+        ALOGI("DelayedEventGenerator exited.");
+    }
+
+    void wakeAfter(std::chrono::nanoseconds waitTime) {
+        std::unique_lock<std::mutex> lock(mMutex);
+        mWakeups.insert(Clock::now() + waitTime);
+        mCondition.notify_one();
+    }
+
+private:
+    void loop() {
+        while (true) {
+            // Lock scope
+            {
+                std::unique_lock<std::mutex> lock(mMutex);
+                mCondition.wait(lock, [this]() { return !mRunning || !mWakeups.empty(); });
+                if (!mRunning && mWakeups.empty()) {
+                    // This thread should only exit once the destructor has been called and all
+                    // wakeups have been processed
+                    return;
+                }
+
+                // At this point, mWakeups will not be empty
+
+                TimePoint target = *(mWakeups.begin());
+                auto status = mCondition.wait_until(lock, target);
+                while (status == std::cv_status::no_timeout) {
+                    // This was either a spurious wakeup or another wakeup was added, so grab the
+                    // oldest point and wait again
+                    target = *(mWakeups.begin());
+                    status = mCondition.wait_until(lock, target);
+                }
+
+                // status must have been timeout, so we can finally clear this point
+                mWakeups.erase(target);
+            }
+            // Callback *without* locks!
+            mOnTimerExpired();
+        }
+    }
+
+    std::function<void()> mOnTimerExpired;
+    std::thread mThread;
+    std::mutex mMutex;
+    std::condition_variable mCondition;
+    bool mRunning = true;
+    std::set<TimePoint> mWakeups;
+};
+
+} // namespace
+
+FakeComposerClient::FakeComposerClient()
+      : mCallbacksOn(false),
+        mClient(nullptr),
+        mCurrentConfig(NULL_DISPLAY_CONFIG),
+        mVsyncEnabled(false),
+        mLayers(),
+        mDelayedEventGenerator(
+                std::make_unique<DelayedEventGenerator>([this]() { this->requestVSync(); })),
+        mSurfaceComposer(nullptr) {}
+
+FakeComposerClient::~FakeComposerClient() {}
+
+void FakeComposerClient::removeClient() {
+    ALOGV("removeClient");
+    // TODO: Ahooga! Only thing current lifetime management choices in
+    // APIs make possible. Sad.
+    delete this;
+}
+
+void FakeComposerClient::enableCallback(bool enable) {
+    ALOGV("enableCallback");
+    mCallbacksOn = enable;
+    if (mCallbacksOn) {
+        mClient->onHotplug(DEFAULT_DISPLAY, IComposerCallback::Connection::CONNECTED);
+    }
+}
+
+void FakeComposerClient::hotplugDisplay(Display display, IComposerCallback::Connection state) {
+    if (mCallbacksOn) {
+        mClient->onHotplug(display, state);
+    }
+}
+
+uint32_t FakeComposerClient::getMaxVirtualDisplayCount() {
+    ALOGV("getMaxVirtualDisplayCount");
+    return 1;
+}
+
+Error FakeComposerClient::createVirtualDisplay(uint32_t /*width*/, uint32_t /*height*/,
+                                               PixelFormat* /*format*/, Display* /*outDisplay*/) {
+    ALOGV("createVirtualDisplay");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::destroyVirtualDisplay(Display /*display*/) {
+    ALOGV("destroyVirtualDisplay");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::createLayer(Display /*display*/, Layer* outLayer) {
+    ALOGV("createLayer");
+    *outLayer = mLayers.size();
+    auto newLayer = std::make_unique<LayerImpl>();
+    mLayers.push_back(std::move(newLayer));
+    return Error::NONE;
+}
+
+Error FakeComposerClient::destroyLayer(Display /*display*/, Layer layer) {
+    ALOGV("destroyLayer");
+    mLayers[layer]->mValid = false;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getActiveConfig(Display /*display*/, Config* outConfig) {
+    ALOGV("getActiveConfig");
+
+    // TODO Assert outConfig != nullptr
+
+    // TODO This is my reading of the
+    // IComposerClient::getActiveConfig, but returning BAD_CONFIG
+    // seems to not fit SurfaceFlinger plans. See version 2 below.
+    // if (mCurrentConfig == NULL_DISPLAY_CONFIG) {
+    //     return Error::BAD_CONFIG;
+    // }
+    //*outConfig = mCurrentConfig;
+    *outConfig = 1; // Very special config for you my friend
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getClientTargetSupport(Display /*display*/, uint32_t /*width*/,
+                                                 uint32_t /*height*/, PixelFormat /*format*/,
+                                                 Dataspace /*dataspace*/) {
+    ALOGV("getClientTargetSupport");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getColorModes(Display /*display*/, hidl_vec<ColorMode>* /*outModes*/) {
+    ALOGV("getColorModes");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getDisplayAttribute(Display display, Config config,
+                                              IComposerClient::Attribute attribute,
+                                              int32_t* outValue) {
+    ALOGV("getDisplayAttribute (%d, %d, %d, %p)", static_cast<int>(display),
+          static_cast<int>(config), static_cast<int>(attribute), outValue);
+
+    // TODO: SOOO much fun to be had with these alone
+    switch (attribute) {
+        case IComposerClient::Attribute::WIDTH:
+            *outValue = 1920;
+            break;
+        case IComposerClient::Attribute::HEIGHT:
+            *outValue = 1080;
+            break;
+        case IComposerClient::Attribute::VSYNC_PERIOD:
+            *outValue = 1666666666;
+            break; // TOOD: Tests break down if lowered to 16ms?
+        case IComposerClient::Attribute::DPI_X:
+            *outValue = 240;
+            break;
+        case IComposerClient::Attribute::DPI_Y:
+            *outValue = 240;
+            break;
+        default:
+            LOG_ALWAYS_FATAL("Say what!?! New attribute");
+    }
+
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getDisplayConfigs(Display /*display*/, hidl_vec<Config>* outConfigs) {
+    ALOGV("getDisplayConfigs");
+    // TODO assert display == 1, outConfigs != nullptr
+
+    outConfigs->resize(1);
+    (*outConfigs)[0] = 1;
+
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getDisplayName(Display /*display*/, hidl_string* /*outName*/) {
+    ALOGV("getDisplayName");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getDisplayType(Display /*display*/,
+                                         IComposerClient::DisplayType* outType) {
+    ALOGV("getDisplayType");
+    // TODO: This setting nothing on the output had no effect on initial trials. Is first display
+    // assumed to be physical?
+    *outType = static_cast<IComposerClient::DisplayType>(HWC2_DISPLAY_TYPE_PHYSICAL);
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getDozeSupport(Display /*display*/, bool* /*outSupport*/) {
+    ALOGV("getDozeSupport");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::getHdrCapabilities(Display /*display*/, hidl_vec<Hdr>* /*outTypes*/,
+                                             float* /*outMaxLuminance*/,
+                                             float* /*outMaxAverageLuminance*/,
+                                             float* /*outMinLuminance*/) {
+    ALOGV("getHdrCapabilities");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setActiveConfig(Display /*display*/, Config config) {
+    ALOGV("setActiveConfig");
+    mCurrentConfig = config;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setColorMode(Display /*display*/, ColorMode /*mode*/) {
+    ALOGV("setColorMode");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setPowerMode(Display /*display*/, IComposerClient::PowerMode /*mode*/) {
+    ALOGV("setPowerMode");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setVsyncEnabled(Display /*display*/, IComposerClient::Vsync enabled) {
+    mVsyncEnabled = (enabled == IComposerClient::Vsync::ENABLE);
+    ALOGV("setVsyncEnabled(%s)", mVsyncEnabled ? "ENABLE" : "DISABLE");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setColorTransform(Display /*display*/, const float* /*matrix*/,
+                                            int32_t /*hint*/) {
+    ALOGV("setColorTransform");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setClientTarget(Display /*display*/, buffer_handle_t /*target*/,
+                                          int32_t /*acquireFence*/, int32_t /*dataspace*/,
+                                          const std::vector<hwc_rect_t>& /*damage*/) {
+    ALOGV("setClientTarget");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setOutputBuffer(Display /*display*/, buffer_handle_t /*buffer*/,
+                                          int32_t /*releaseFence*/) {
+    ALOGV("setOutputBuffer");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::validateDisplay(
+        Display /*display*/, std::vector<Layer>* /*outChangedLayers*/,
+        std::vector<IComposerClient::Composition>* /*outCompositionTypes*/,
+        uint32_t* /*outDisplayRequestMask*/, std::vector<Layer>* /*outRequestedLayers*/,
+        std::vector<uint32_t>* /*outRequestMasks*/) {
+    ALOGV("validateDisplay");
+    // TODO: Assume touching nothing means All Korrekt!
+    return Error::NONE;
+}
+
+Error FakeComposerClient::acceptDisplayChanges(Display /*display*/) {
+    ALOGV("acceptDisplayChanges");
+    // Didn't ask for changes because software is omnipotent.
+    return Error::NONE;
+}
+
+bool layerZOrdering(const std::unique_ptr<FrameRect>& a, const std::unique_ptr<FrameRect>& b) {
+    return a->z <= b->z;
+}
+
+Error FakeComposerClient::presentDisplay(Display /*display*/, int32_t* /*outPresentFence*/,
+                                         std::vector<Layer>* /*outLayers*/,
+                                         std::vector<int32_t>* /*outReleaseFences*/) {
+    ALOGV("presentDisplay");
+    // TODO Leaving layers and their fences out for now. Doing so
+    // means that we've already processed everything. Important to
+    // test that the fences are respected, though. (How?)
+
+    std::unique_ptr<Frame> newFrame(new Frame);
+    for (uint64_t layer = 0; layer < mLayers.size(); layer++) {
+        const LayerImpl& layerImpl = *mLayers[layer];
+
+        if (!layerImpl.mValid) continue;
+
+        auto rect = std::make_unique<FrameRect>(layer, layerImpl.mRenderState, layerImpl.mZ);
+        newFrame->rectangles.push_back(std::move(rect));
+    }
+    std::sort(newFrame->rectangles.begin(), newFrame->rectangles.end(), layerZOrdering);
+    {
+        Mutex::Autolock _l(mStateMutex);
+        mFrames.push_back(std::move(newFrame));
+        mFramesAvailable.broadcast();
+    }
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerCursorPosition(Display /*display*/, Layer /*layer*/,
+                                                 int32_t /*x*/, int32_t /*y*/) {
+    ALOGV("setLayerCursorPosition");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerBuffer(Display /*display*/, Layer layer, buffer_handle_t buffer,
+                                         int32_t acquireFence) {
+    ALOGV("setLayerBuffer");
+    LayerImpl& l = getLayerImpl(layer);
+    if (buffer != l.mRenderState.mBuffer) {
+        l.mRenderState.mSwapCount++; // TODO: Is setting to same value a swap or not?
+    }
+    l.mRenderState.mBuffer = buffer;
+    l.mRenderState.mAcquireFence = acquireFence;
+
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerSurfaceDamage(Display /*display*/, Layer /*layer*/,
+                                                const std::vector<hwc_rect_t>& /*damage*/) {
+    ALOGV("setLayerSurfaceDamage");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerBlendMode(Display /*display*/, Layer layer, int32_t mode) {
+    ALOGV("setLayerBlendMode");
+    getLayerImpl(layer).mRenderState.mBlendMode = static_cast<hwc2_blend_mode_t>(mode);
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerColor(Display /*display*/, Layer layer,
+                                        IComposerClient::Color color) {
+    ALOGV("setLayerColor");
+    getLayerImpl(layer).mRenderState.mLayerColor.r = color.r;
+    getLayerImpl(layer).mRenderState.mLayerColor.g = color.g;
+    getLayerImpl(layer).mRenderState.mLayerColor.b = color.b;
+    getLayerImpl(layer).mRenderState.mLayerColor.a = color.a;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerCompositionType(Display /*display*/, Layer /*layer*/,
+                                                  int32_t /*type*/) {
+    ALOGV("setLayerCompositionType");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerDataspace(Display /*display*/, Layer /*layer*/,
+                                            int32_t /*dataspace*/) {
+    ALOGV("setLayerDataspace");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerDisplayFrame(Display /*display*/, Layer layer,
+                                               const hwc_rect_t& frame) {
+    ALOGV("setLayerDisplayFrame (%d, %d, %d, %d)", frame.left, frame.top, frame.right,
+          frame.bottom);
+    getLayerImpl(layer).mRenderState.mDisplayFrame = frame;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerPlaneAlpha(Display /*display*/, Layer layer, float alpha) {
+    ALOGV("setLayerPlaneAlpha");
+    getLayerImpl(layer).mRenderState.mPlaneAlpha = alpha;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerSidebandStream(Display /*display*/, Layer /*layer*/,
+                                                 buffer_handle_t /*stream*/) {
+    ALOGV("setLayerSidebandStream");
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerSourceCrop(Display /*display*/, Layer layer,
+                                             const hwc_frect_t& crop) {
+    ALOGV("setLayerSourceCrop");
+    getLayerImpl(layer).mRenderState.mSourceCrop = crop;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerTransform(Display /*display*/, Layer layer, int32_t transform) {
+    ALOGV("setLayerTransform");
+    getLayerImpl(layer).mRenderState.mTransform = static_cast<hwc_transform_t>(transform);
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerVisibleRegion(Display /*display*/, Layer layer,
+                                                const std::vector<hwc_rect_t>& visible) {
+    ALOGV("setLayerVisibleRegion");
+    getLayerImpl(layer).mRenderState.mVisibleRegion = visible;
+    return Error::NONE;
+}
+
+Error FakeComposerClient::setLayerZOrder(Display /*display*/, Layer layer, uint32_t z) {
+    ALOGV("setLayerZOrder");
+    getLayerImpl(layer).mZ = z;
+    return Error::NONE;
+}
+
+//////////////////////////////////////////////////////////////////
+
+void FakeComposerClient::setClient(ComposerClient* client) {
+    mClient = client;
+}
+
+void FakeComposerClient::requestVSync(uint64_t vsyncTime) {
+    if (mCallbacksOn) {
+        uint64_t timestamp = vsyncTime;
+        ALOGV("Vsync");
+        if (timestamp == 0) {
+            struct timespec ts;
+            clock_gettime(CLOCK_MONOTONIC, &ts);
+            timestamp = ts.tv_sec * 1000 * 1000 * 1000 + ts.tv_nsec;
+        }
+        if (mSurfaceComposer != nullptr) {
+            mSurfaceComposer->injectVSync(timestamp);
+        } else {
+            mClient->onVsync(DEFAULT_DISPLAY, timestamp);
+        }
+    }
+}
+
+void FakeComposerClient::runVSyncAfter(std::chrono::nanoseconds wait) {
+    mDelayedEventGenerator->wakeAfter(wait);
+}
+
+LayerImpl& FakeComposerClient::getLayerImpl(Layer handle) {
+    // TODO Change these to an internal state check that can be
+    // invoked from the gtest? GTest macros do not seem all that safe
+    // when used outside the test class
+    EXPECT_GE(handle, static_cast<Layer>(0));
+    EXPECT_LT(handle, mLayers.size());
+    return *(mLayers[handle]);
+}
+
+int FakeComposerClient::getFrameCount() const {
+    return mFrames.size();
+}
+
+static std::vector<RenderState> extractRenderState(
+        const std::vector<std::unique_ptr<FrameRect>>& internalRects) {
+    std::vector<RenderState> result;
+    result.reserve(internalRects.size());
+    for (const std::unique_ptr<FrameRect>& rect : internalRects) {
+        result.push_back(rect->renderState);
+    }
+    return result;
+}
+
+std::vector<RenderState> FakeComposerClient::getFrameRects(int frame) const {
+    Mutex::Autolock _l(mStateMutex);
+    return extractRenderState(mFrames[frame]->rectangles);
+}
+
+std::vector<RenderState> FakeComposerClient::getLatestFrame() const {
+    Mutex::Autolock _l(mStateMutex);
+    return extractRenderState(mFrames[mFrames.size() - 1]->rectangles);
+}
+
+void FakeComposerClient::runVSyncAndWait(std::chrono::nanoseconds maxWait) {
+    int currentFrame = 0;
+    {
+        Mutex::Autolock _l(mStateMutex); // I hope this is ok...
+        currentFrame = static_cast<int>(mFrames.size());
+        requestVSync();
+    }
+    waitUntilFrame(currentFrame + 1, maxWait);
+}
+
+void FakeComposerClient::waitUntilFrame(int targetFrame, std::chrono::nanoseconds maxWait) const {
+    Mutex::Autolock _l(mStateMutex);
+    while (mFrames.size() < static_cast<size_t>(targetFrame)) {
+        android::status_t result = mFramesAvailable.waitRelative(mStateMutex, maxWait.count());
+        if (result == android::TIMED_OUT) {
+            ALOGE("Waiting for frame %d (at frame %zu now) timed out after %lld ns", targetFrame,
+                  mFrames.size(), maxWait.count());
+            return;
+        }
+    }
+}
+
+void FakeComposerClient::clearFrames() {
+    Mutex::Autolock _l(mStateMutex);
+    mFrames.clear();
+    for (const std::unique_ptr<LayerImpl>& layer : mLayers) {
+        if (layer->mValid) {
+            layer->mRenderState.mSwapCount = 0;
+        }
+    }
+}
+
+void FakeComposerClient::onSurfaceFlingerStart() {
+    mSurfaceComposer == nullptr;
+    do {
+        mSurfaceComposer = new android::SurfaceComposerClient;
+        android::status_t initResult = mSurfaceComposer->initCheck();
+        if (initResult != android::NO_ERROR) {
+            ALOGD("Init result: %d", initResult);
+            mSurfaceComposer = nullptr;
+            std::this_thread::sleep_for(10ms);
+        }
+    } while (mSurfaceComposer == nullptr);
+    ALOGD("SurfaceComposerClient created");
+    mSurfaceComposer->enableVSyncInjections(true);
+}
+
+void FakeComposerClient::onSurfaceFlingerStop() {
+    mSurfaceComposer->dispose();
+    mSurfaceComposer.clear();
+}
+
+// Includes destroyed layers, stored in order of creation.
+int FakeComposerClient::getLayerCount() const {
+    return mLayers.size();
+}
+
+Layer FakeComposerClient::getLayer(size_t index) const {
+    // NOTE: If/when passing calls through to actual implementation,
+    // this might get more involving.
+    return static_cast<Layer>(index);
+}
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerClient.h b/services/surfaceflinger/tests/fakehwc/FakeComposerClient.h
new file mode 100644
index 0000000..294abb2
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerClient.h
@@ -0,0 +1,146 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "ComposerClient.h"
+#include "RenderState.h"
+
+#include <utils/Condition.h>
+
+#include <chrono>
+
+using namespace android::hardware::graphics::composer::V2_1;
+using namespace android::hardware::graphics::composer::V2_1::implementation;
+using namespace android::hardware;
+using namespace std::chrono_literals;
+
+namespace {
+class LayerImpl;
+class Frame;
+class DelayedEventGenerator;
+} // namespace
+
+namespace android {
+class SurfaceComposerClient;
+} // namespace android
+
+namespace sftest {
+
+class FakeComposerClient : public ComposerBase {
+public:
+    FakeComposerClient();
+    virtual ~FakeComposerClient();
+
+    void removeClient() override;
+    void enableCallback(bool enable) override;
+    uint32_t getMaxVirtualDisplayCount() override;
+    Error createVirtualDisplay(uint32_t width, uint32_t height, PixelFormat* format,
+                               Display* outDisplay) override;
+    Error destroyVirtualDisplay(Display display) override;
+    Error createLayer(Display display, Layer* outLayer) override;
+    Error destroyLayer(Display display, Layer layer) override;
+
+    Error getActiveConfig(Display display, Config* outConfig) override;
+    Error getClientTargetSupport(Display display, uint32_t width, uint32_t height,
+                                 PixelFormat format, Dataspace dataspace) override;
+    Error getColorModes(Display display, hidl_vec<ColorMode>* outModes) override;
+    Error getDisplayAttribute(Display display, Config config, IComposerClient::Attribute attribute,
+                              int32_t* outValue) override;
+    Error getDisplayConfigs(Display display, hidl_vec<Config>* outConfigs) override;
+    Error getDisplayName(Display display, hidl_string* outName) override;
+    Error getDisplayType(Display display, IComposerClient::DisplayType* outType) override;
+    Error getDozeSupport(Display display, bool* outSupport) override;
+    Error getHdrCapabilities(Display display, hidl_vec<Hdr>* outTypes, float* outMaxLuminance,
+                             float* outMaxAverageLuminance, float* outMinLuminance) override;
+
+    Error setActiveConfig(Display display, Config config) override;
+    Error setColorMode(Display display, ColorMode mode) override;
+    Error setPowerMode(Display display, IComposerClient::PowerMode mode) override;
+    Error setVsyncEnabled(Display display, IComposerClient::Vsync enabled) override;
+
+    Error setColorTransform(Display display, const float* matrix, int32_t hint) override;
+    Error setClientTarget(Display display, buffer_handle_t target, int32_t acquireFence,
+                          int32_t dataspace, const std::vector<hwc_rect_t>& damage) override;
+    Error setOutputBuffer(Display display, buffer_handle_t buffer, int32_t releaseFence) override;
+    Error validateDisplay(Display display, std::vector<Layer>* outChangedLayers,
+                          std::vector<IComposerClient::Composition>* outCompositionTypes,
+                          uint32_t* outDisplayRequestMask, std::vector<Layer>* outRequestedLayers,
+                          std::vector<uint32_t>* outRequestMasks) override;
+    Error acceptDisplayChanges(Display display) override;
+    Error presentDisplay(Display display, int32_t* outPresentFence, std::vector<Layer>* outLayers,
+                         std::vector<int32_t>* outReleaseFences) override;
+
+    Error setLayerCursorPosition(Display display, Layer layer, int32_t x, int32_t y) override;
+    Error setLayerBuffer(Display display, Layer layer, buffer_handle_t buffer,
+                         int32_t acquireFence) override;
+    Error setLayerSurfaceDamage(Display display, Layer layer,
+                                const std::vector<hwc_rect_t>& damage) override;
+    Error setLayerBlendMode(Display display, Layer layer, int32_t mode) override;
+    Error setLayerColor(Display display, Layer layer, IComposerClient::Color color) override;
+    Error setLayerCompositionType(Display display, Layer layer, int32_t type) override;
+    Error setLayerDataspace(Display display, Layer layer, int32_t dataspace) override;
+    Error setLayerDisplayFrame(Display display, Layer layer, const hwc_rect_t& frame) override;
+    Error setLayerPlaneAlpha(Display display, Layer layer, float alpha) override;
+    Error setLayerSidebandStream(Display display, Layer layer, buffer_handle_t stream) override;
+    Error setLayerSourceCrop(Display display, Layer layer, const hwc_frect_t& crop) override;
+    Error setLayerTransform(Display display, Layer layer, int32_t transform) override;
+    Error setLayerVisibleRegion(Display display, Layer layer,
+                                const std::vector<hwc_rect_t>& visible) override;
+    Error setLayerZOrder(Display display, Layer layer, uint32_t z) override;
+
+    void setClient(ComposerClient* client);
+
+    void requestVSync(uint64_t vsyncTime = 0);
+    // We don't want tests hanging, so always use a timeout. Remember
+    // to always check the number of frames with test ASSERT_!
+    // Wait until next frame is rendered after requesting vsync.
+    void runVSyncAndWait(std::chrono::nanoseconds maxWait = 100ms);
+    void runVSyncAfter(std::chrono::nanoseconds wait);
+
+    int getFrameCount() const;
+    // We don't want tests hanging, so always use a timeout. Remember
+    // to always check the number of frames with test ASSERT_!
+    void waitUntilFrame(int targetFrame, std::chrono::nanoseconds maxWait = 100ms) const;
+    std::vector<RenderState> getFrameRects(int frame) const;
+    std::vector<RenderState> getLatestFrame() const;
+    void clearFrames();
+
+    void onSurfaceFlingerStart();
+    void onSurfaceFlingerStop();
+
+    int getLayerCount() const;
+    Layer getLayer(size_t index) const;
+
+    void hotplugDisplay(Display display, IComposerCallback::Connection state);
+
+private:
+    LayerImpl& getLayerImpl(Layer handle);
+
+    bool mCallbacksOn;
+    ComposerClient* mClient;
+    Config mCurrentConfig;
+    bool mVsyncEnabled;
+    std::vector<std::unique_ptr<LayerImpl>> mLayers;
+    std::vector<std::unique_ptr<Frame>> mFrames;
+    // Using a pointer to hide the implementation into the CPP file.
+    std::unique_ptr<DelayedEventGenerator> mDelayedEventGenerator;
+    android::sp<android::SurfaceComposerClient> mSurfaceComposer; // For VSync injections
+    mutable android::Mutex mStateMutex;
+    mutable android::Condition mFramesAvailable;
+};
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerService.cpp b/services/surfaceflinger/tests/fakehwc/FakeComposerService.cpp
new file mode 100644
index 0000000..c411604
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerService.cpp
@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_NDEBUG 0
+#undef LOG_TAG
+#define LOG_TAG "FakeHwcService"
+#include <log/log.h>
+
+#include "FakeComposerService.h"
+
+using namespace android::hardware;
+
+namespace sftest {
+
+FakeComposerService::FakeComposerService(android::sp<ComposerClient>& client) : mClient(client) {}
+
+FakeComposerService::~FakeComposerService() {
+    ALOGI("Maybe killing client %p", mClient.get());
+    // Rely on sp to kill the client.
+}
+
+Return<void> FakeComposerService::getCapabilities(getCapabilities_cb hidl_cb) {
+    ALOGI("FakeComposerService::getCapabilities");
+    hidl_cb(hidl_vec<Capability>());
+    return Void();
+}
+
+Return<void> FakeComposerService::dumpDebugInfo(dumpDebugInfo_cb hidl_cb) {
+    ALOGI("FakeComposerService::dumpDebugInfo");
+    hidl_cb(hidl_string());
+    return Void();
+}
+
+Return<void> FakeComposerService::createClient(createClient_cb hidl_cb) {
+    ALOGI("FakeComposerService::createClient %p", mClient.get());
+    mClient->initialize();
+    hidl_cb(Error::NONE, mClient);
+    return Void();
+}
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerService.h b/services/surfaceflinger/tests/fakehwc/FakeComposerService.h
new file mode 100644
index 0000000..5204084
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerService.h
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "ComposerClient.h"
+
+using namespace android::hardware::graphics::composer::V2_1;
+using namespace android::hardware::graphics::composer::V2_1::implementation;
+using android::hardware::Return;
+
+namespace sftest {
+
+class FakeComposerService : public IComposer {
+public:
+    FakeComposerService(android::sp<ComposerClient>& client);
+    virtual ~FakeComposerService();
+
+    Return<void> getCapabilities(getCapabilities_cb hidl_cb) override;
+    Return<void> dumpDebugInfo(dumpDebugInfo_cb hidl_cb) override;
+    Return<void> createClient(createClient_cb hidl_cb) override;
+
+private:
+    android::sp<ComposerClient> mClient;
+};
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.cpp b/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.cpp
new file mode 100644
index 0000000..51956ec
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.cpp
@@ -0,0 +1,183 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_NDEBUG 0
+#undef LOG_TAG
+#define LOG_TAG "FakeHwcUtil"
+#include <log/log.h>
+
+#include "FakeComposerUtils.h"
+#include "RenderState.h"
+
+#include "SurfaceFlinger.h" // Get the name of the service...
+
+#include <binder/IServiceManager.h>
+
+#include <cutils/properties.h>
+
+#include <iomanip>
+#include <thread>
+
+using android::String16;
+using android::sp;
+using namespace std::chrono_literals;
+using namespace sftest;
+using std::setw;
+
+namespace sftest {
+
+// clang-format off
+inline void printSourceRectAligned(::std::ostream& os, const hwc_frect_t& sourceRect, int align) {
+    os << std::fixed << std::setprecision(1) << "("
+       << setw(align) << sourceRect.left << setw(0) << ","
+       << setw(align) << sourceRect.top << setw(0) << ","
+       << setw(align) << sourceRect.right << setw(0) << ","
+       << setw(align) << sourceRect.bottom << setw(0) << ")";
+}
+
+inline void printDisplayRectAligned(::std::ostream& os, const hwc_rect_t& displayRect, int align) {
+    os << "("
+       << setw(align) << displayRect.left << setw(0) << ","
+       << setw(align) << displayRect.top << setw(0) << ","
+       << setw(align) << displayRect.right << setw(0) << ","
+       << setw(align) << displayRect.bottom << setw(0) << ")";
+}
+// clang-format on
+
+inline ::std::ostream& operator<<(::std::ostream& os, const sftest::RenderState& state) {
+    printSourceRectAligned(os, state.mSourceCrop, 7);
+    os << "->";
+    printDisplayRectAligned(os, state.mDisplayFrame, 5);
+    return os << " Swaps:" << state.mSwapCount << " Alpha:" << std::setprecision(3)
+              << state.mPlaneAlpha << " Xform:" << state.mTransform;
+}
+
+// Helper for verifying the parts of the RenderState
+template <typename T>
+bool valuesMatch(::testing::AssertionResult& message, const T& ref, const T& val,
+                 const char* name) {
+    if (ref != val) {
+        message = message << "Expected " << name << ":" << ref << ", got:" << val << ".";
+        return false;
+    }
+    return true;
+}
+
+::testing::AssertionResult rectsAreSame(const RenderState& ref, const RenderState& val) {
+    // TODO: Message could start as success and be assigned as failure.
+    // Only problem is that utility assumes it to be failure and just adds stuff. Would
+    // need still special case the initial failure in the utility?
+    // TODO: ... or would it be possible to break this back to gtest primitives?
+    ::testing::AssertionResult message = ::testing::AssertionFailure();
+    bool passes = true;
+
+    // The work here is mostly about providing good log strings for differences
+    passes &= valuesMatch(message, ref.mDisplayFrame, val.mDisplayFrame, "display frame");
+    passes &= valuesMatch(message, ref.mPlaneAlpha, val.mPlaneAlpha, "alpha");
+    passes &= valuesMatch(message, ref.mSwapCount, val.mSwapCount, "swap count");
+    passes &= valuesMatch(message, ref.mSourceCrop, val.mSourceCrop, "source crop");
+    // ... add more
+    if (passes) {
+        return ::testing::AssertionSuccess();
+    }
+    return message;
+}
+
+::testing::AssertionResult framesAreSame(const std::vector<RenderState>& ref,
+                                         const std::vector<RenderState>& val) {
+    ::testing::AssertionResult message = ::testing::AssertionFailure();
+    bool passed = true;
+    if (ref.size() != val.size()) {
+        message << "Expected " << ref.size() << " rects, got " << val.size() << ".";
+        passed = false;
+    }
+    for (size_t rectIndex = 0; rectIndex < std::min(ref.size(), val.size()); rectIndex++) {
+        ::testing::AssertionResult rectResult = rectsAreSame(ref[rectIndex], val[rectIndex]);
+        if (rectResult == false) {
+            message << "First different rect at " << rectIndex << ": " << rectResult.message();
+            passed = false;
+            break;
+        }
+    }
+
+    if (passed) {
+        return ::testing::AssertionSuccess();
+    } else {
+        message << "\nReference:";
+        for (auto state = ref.begin(); state != ref.end(); ++state) {
+            message << "\n" << *state;
+        }
+        message << "\nActual:";
+        for (auto state = val.begin(); state != val.end(); ++state) {
+            message << "\n" << *state;
+        }
+    }
+    return message;
+}
+
+void startSurfaceFlinger() {
+    ALOGI("Start SurfaceFlinger");
+    system("start surfaceflinger");
+
+    sp<android::IServiceManager> sm(android::defaultServiceManager());
+    sp<android::IBinder> sf;
+    while (sf == nullptr) {
+        std::this_thread::sleep_for(10ms);
+        sf = sm->checkService(String16(android::SurfaceFlinger::getServiceName()));
+    }
+    ALOGV("SurfaceFlinger running");
+}
+
+void stopSurfaceFlinger() {
+    ALOGI("Stop SurfaceFlinger");
+    system("stop surfaceflinger");
+    sp<android::IServiceManager> sm(android::defaultServiceManager());
+    sp<android::IBinder> sf;
+    while (sf != nullptr) {
+        std::this_thread::sleep_for(10ms);
+        sf = sm->checkService(String16(android::SurfaceFlinger::getServiceName()));
+    }
+    ALOGV("SurfaceFlinger stopped");
+}
+
+////////////////////////////////////////////////
+
+void FakeHwcEnvironment::SetUp() {
+    ALOGI("Test env setup");
+    system("setenforce 0");
+    system("stop");
+    property_set("debug.sf.nobootanimation", "1");
+    {
+        char value[PROPERTY_VALUE_MAX];
+        property_get("debug.sf.nobootanimation", value, "0");
+        LOG_FATAL_IF(atoi(value) != 1, "boot skip not set");
+    }
+    // TODO: Try registering the mock as the default service instead.
+    property_set("debug.sf.hwc_service_name", "mock");
+    // This allows the SurfaceFlinger to load a HIDL service not listed in manifest files.
+    property_set("debug.sf.treble_testing_override", "true");
+}
+
+void FakeHwcEnvironment::TearDown() {
+    ALOGI("Test env tear down");
+    system("stop");
+    // Wait for mock call signaling teardown?
+    property_set("debug.sf.nobootanimation", "0");
+    property_set("debug.sf.hwc_service_name", "default");
+    ALOGI("Test env tear down - done");
+}
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.h b/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.h
new file mode 100644
index 0000000..74dc0e5
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/FakeComposerUtils.h
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include "FakeComposerClient.h"
+
+#include <gui/SurfaceComposerClient.h>
+
+#include <hardware/hwcomposer_defs.h>
+
+#include <log/log.h>
+
+#include <gtest/gtest.h>
+
+// clang-format off
+// Note: This needs to reside in the global namespace for the GTest to use it
+inline ::std::ostream& operator<<(::std::ostream& os, const hwc_rect_t& rect) {
+    return os << "(" << rect.left << ","
+              << rect.top << ","
+              << rect.right << ","
+              << rect.bottom << ")";
+}
+
+inline ::std::ostream& operator<<(::std::ostream& os, const hwc_frect_t& rect) {
+    return os << "(" << rect.left << ","
+              << rect.top << ","
+              << rect.right << ","
+              << rect.bottom << ")";
+}
+// clang-format on
+
+namespace sftest {
+
+class RenderState;
+
+// clang-format off
+inline bool operator==(const hwc_rect_t& a, const hwc_rect_t& b) {
+    return a.top == b.top &&
+            a.left == b.left &&
+            a.bottom == b.bottom &&
+            a.right == b.right;
+}
+
+inline bool operator==(const hwc_frect_t& a, const hwc_frect_t& b) {
+    return a.top == b.top &&
+            a.left == b.left &&
+            a.bottom == b.bottom &&
+            a.right == b.right;
+}
+// clang-format on
+
+inline bool operator!=(const hwc_rect_t& a, const hwc_rect_t& b) {
+    return !(a == b);
+}
+
+inline bool operator!=(const hwc_frect_t& a, const hwc_frect_t& b) {
+    return !(a == b);
+}
+
+::testing::AssertionResult rectsAreSame(const RenderState& ref, const RenderState& val);
+::testing::AssertionResult framesAreSame(const std::vector<RenderState>& ref,
+                                         const std::vector<RenderState>& val);
+
+void startSurfaceFlinger();
+void stopSurfaceFlinger();
+
+class FakeHwcEnvironment : public ::testing::Environment {
+public:
+    virtual ~FakeHwcEnvironment() {}
+    void SetUp() override;
+    void TearDown() override;
+};
+
+/*
+ * All surface state changes are supposed to happen inside a global
+ * transaction. GlobalTransactionScope object at the beginning of
+ * scope automates the process. The resulting scope gives a visual cue
+ * on the span of the transaction as well.
+ *
+ * Closing the transaction is synchronous, i.e., it waits for
+ * SurfaceFlinger to composite one frame. Now, the FakeComposerClient
+ * is built to explicitly request vsyncs one at the time. A delayed
+ * request must be made before closing the transaction or the test
+ * thread stalls until SurfaceFlinger does an emergency vsync by
+ * itself. GlobalTransactionScope encapsulates this vsync magic.
+ */
+class GlobalTransactionScope {
+public:
+    GlobalTransactionScope(FakeComposerClient& composer) : mComposer(composer) {
+        android::SurfaceComposerClient::openGlobalTransaction();
+    }
+    ~GlobalTransactionScope() {
+        int frameCount = mComposer.getFrameCount();
+        mComposer.runVSyncAfter(1ms);
+        android::SurfaceComposerClient::closeGlobalTransaction(true);
+        // Make sure that exactly one frame has been rendered.
+        mComposer.waitUntilFrame(frameCount + 1);
+        LOG_ALWAYS_FATAL_IF(frameCount + 1 != mComposer.getFrameCount(),
+                            "Unexpected frame advance. Delta: %d",
+                            mComposer.getFrameCount() - frameCount);
+    }
+    FakeComposerClient& mComposer;
+};
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/RenderState.h b/services/surfaceflinger/tests/fakehwc/RenderState.h
new file mode 100644
index 0000000..0059289
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/RenderState.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <hardware/hwcomposer2.h>
+
+#include <vector>
+
+namespace sftest {
+// Description of a rendered rectangle.  Should only contain
+// instructions necessary to rasterize the rectangle. The full scene
+// is given as a sorted list of rectangles, bottom layer at index 0.
+class RenderState {
+public:
+    RenderState() = default;
+    // Default copy-ctor
+
+    hwc_rect_t mDisplayFrame = {0, 0, 0, 0};
+    hwc_frect_t mSourceCrop = {0.f, 0.f, 0.f, 0.f};
+    std::vector<hwc_rect_t> mVisibleRegion;
+    hwc2_blend_mode_t mBlendMode = HWC2_BLEND_MODE_NONE;
+    buffer_handle_t mBuffer = 0;
+    uint32_t mSwapCount = 0;   // How many set buffer calls to the layer.
+    int32_t mAcquireFence = 0; // Probably should not be here.
+    float mPlaneAlpha = 0.f;
+    hwc_color_t mLayerColor = {0, 0, 0, 0};
+    hwc_transform_t mTransform = static_cast<hwc_transform_t>(0);
+};
+
+} // namespace sftest
diff --git a/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
new file mode 100644
index 0000000..8902ede
--- /dev/null
+++ b/services/surfaceflinger/tests/fakehwc/SFFakeHwc_test.cpp
@@ -0,0 +1,1306 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// #define LOG_NDEBUG 0
+#undef LOG_TAG
+#define LOG_TAG "FakeHwcTest"
+
+#include "FakeComposerClient.h"
+#include "FakeComposerService.h"
+#include "FakeComposerUtils.h"
+
+#include <gui/ISurfaceComposer.h>
+#include <gui/LayerDebugInfo.h>
+#include <gui/Surface.h>
+#include <gui/SurfaceComposerClient.h>
+
+#include <private/gui/ComposerService.h>
+#include <private/gui/LayerState.h>
+
+#include <ui/DisplayInfo.h>
+
+#include <android/native_window.h>
+
+#include <android/hidl/manager/1.0/IServiceManager.h>
+
+#include <hwbinder/ProcessState.h>
+
+#include <binder/ProcessState.h>
+
+#include <log/log.h>
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <limits>
+
+using namespace std::chrono_literals;
+
+using namespace android;
+using namespace android::hardware;
+
+using namespace sftest;
+
+namespace {
+
+// Mock test helpers
+using ::testing::Invoke;
+using ::testing::Return;
+using ::testing::SetArgPointee;
+using ::testing::_;
+
+///////////////////////////////////////////////
+
+struct TestColor {
+public:
+    uint8_t r;
+    uint8_t g;
+    uint8_t b;
+    uint8_t a;
+};
+
+constexpr static TestColor RED = {195, 63, 63, 255};
+constexpr static TestColor LIGHT_RED = {255, 177, 177, 255};
+constexpr static TestColor GREEN = {63, 195, 63, 255};
+constexpr static TestColor BLUE = {63, 63, 195, 255};
+constexpr static TestColor DARK_GRAY = {63, 63, 63, 255};
+constexpr static TestColor LIGHT_GRAY = {200, 200, 200, 255};
+
+// Fill an RGBA_8888 formatted surface with a single color.
+static void fillSurfaceRGBA8(const sp<SurfaceControl>& sc, const TestColor& color,
+                             bool unlock = true) {
+    ANativeWindow_Buffer outBuffer;
+    sp<Surface> s = sc->getSurface();
+    ASSERT_TRUE(s != nullptr);
+    ASSERT_EQ(NO_ERROR, s->lock(&outBuffer, nullptr));
+    uint8_t* img = reinterpret_cast<uint8_t*>(outBuffer.bits);
+    for (int y = 0; y < outBuffer.height; y++) {
+        for (int x = 0; x < outBuffer.width; x++) {
+            uint8_t* pixel = img + (4 * (y * outBuffer.stride + x));
+            pixel[0] = color.r;
+            pixel[1] = color.g;
+            pixel[2] = color.b;
+            pixel[3] = color.a;
+        }
+    }
+    if (unlock) {
+        ASSERT_EQ(NO_ERROR, s->unlockAndPost());
+    }
+}
+
+inline RenderState makeSimpleRect(int left, int top, int right, int bottom) {
+    RenderState res;
+    res.mDisplayFrame = hwc_rect_t{left, top, right, bottom};
+    res.mPlaneAlpha = 1.0f;
+    res.mSwapCount = 0;
+    res.mSourceCrop = hwc_frect_t{0.f, 0.f, static_cast<float>(right - left),
+                                  static_cast<float>(bottom - top)};
+    return res;
+}
+
+inline RenderState makeSimpleRect(unsigned int left, unsigned int top, unsigned int right,
+                                  unsigned int bottom) {
+    EXPECT_LE(left, static_cast<unsigned int>(INT_MAX));
+    EXPECT_LE(top, static_cast<unsigned int>(INT_MAX));
+    EXPECT_LE(right, static_cast<unsigned int>(INT_MAX));
+    EXPECT_LE(bottom, static_cast<unsigned int>(INT_MAX));
+    return makeSimpleRect(static_cast<int>(left), static_cast<int>(top), static_cast<int>(right),
+                          static_cast<int>(bottom));
+}
+
+////////////////////////////////////////////////
+
+class DisplayTest : public ::testing::Test {
+public:
+    class MockComposerClient : public FakeComposerClient {
+    public:
+        MOCK_METHOD2(getDisplayType, Error(Display display, ComposerClient::DisplayType* outType));
+        MOCK_METHOD4(getDisplayAttribute,
+                     Error(Display display, Config config, IComposerClient::Attribute attribute,
+                           int32_t* outValue));
+
+        // Re-routing to basic fake implementation
+        Error getDisplayAttributeFake(Display display, Config config,
+                                      IComposerClient::Attribute attribute, int32_t* outValue) {
+            return FakeComposerClient::getDisplayAttribute(display, config, attribute, outValue);
+        }
+    };
+
+protected:
+    void SetUp() override;
+    void TearDown() override;
+
+    sp<IComposer> mFakeService;
+    sp<SurfaceComposerClient> mComposerClient;
+
+    MockComposerClient* mMockComposer;
+};
+
+void DisplayTest::SetUp() {
+    // TODO: The mMockComposer should be a unique_ptr, but it needs to
+    // outlive the test class.  Currently ComposerClient only dies
+    // when the service is replaced. The Mock deletes itself when
+    // removeClient is called on it, which is ugly.  This can be
+    // changed if HIDL ServiceManager allows removing services or
+    // ComposerClient starts taking the ownership of the contained
+    // implementation class. Moving the fake class to the HWC2
+    // interface instead of the current Composer interface might also
+    // change the situation.
+    mMockComposer = new MockComposerClient;
+    sp<ComposerClient> client = new ComposerClient(*mMockComposer);
+    mMockComposer->setClient(client.get());
+    mFakeService = new FakeComposerService(client);
+    mFakeService->registerAsService("mock");
+
+    android::hardware::ProcessState::self()->startThreadPool();
+    android::ProcessState::self()->startThreadPool();
+
+    EXPECT_CALL(*mMockComposer, getDisplayType(1, _))
+            .WillOnce(DoAll(SetArgPointee<1>(IComposerClient::DisplayType::PHYSICAL),
+                            Return(Error::NONE)));
+    // Seems to be doubled right now, once for display ID 1 and once for 0. This sounds fishy
+    // but encoding that here exactly.
+    EXPECT_CALL(*mMockComposer, getDisplayAttribute(1, 1, _, _))
+            .Times(5)
+            .WillRepeatedly(Invoke(mMockComposer, &MockComposerClient::getDisplayAttributeFake));
+    // TODO: Find out what code is generating the ID 0.
+    EXPECT_CALL(*mMockComposer, getDisplayAttribute(0, 1, _, _))
+            .Times(5)
+            .WillRepeatedly(Invoke(mMockComposer, &MockComposerClient::getDisplayAttributeFake));
+
+    startSurfaceFlinger();
+
+    // Fake composer wants to enable VSync injection
+    mMockComposer->onSurfaceFlingerStart();
+
+    mComposerClient = new SurfaceComposerClient;
+    ASSERT_EQ(NO_ERROR, mComposerClient->initCheck());
+}
+
+void DisplayTest::TearDown() {
+    mComposerClient->dispose();
+    mComposerClient = nullptr;
+
+    // Fake composer needs to release SurfaceComposerClient before the stop.
+    mMockComposer->onSurfaceFlingerStop();
+    stopSurfaceFlinger();
+
+    mFakeService = nullptr;
+    // TODO: Currently deleted in FakeComposerClient::removeClient(). Devise better lifetime
+    // management.
+    mMockComposer = nullptr;
+}
+
+TEST_F(DisplayTest, Hotplug) {
+    ALOGD("DisplayTest::Hotplug");
+
+    EXPECT_CALL(*mMockComposer, getDisplayType(2, _))
+            .Times(2)
+            .WillRepeatedly(DoAll(SetArgPointee<1>(IComposerClient::DisplayType::PHYSICAL),
+                                  Return(Error::NONE)));
+    // The attribute queries will get done twice. This is for defaults
+    EXPECT_CALL(*mMockComposer, getDisplayAttribute(2, 1, _, _))
+            .Times(2 * 3)
+            .WillRepeatedly(Invoke(mMockComposer, &MockComposerClient::getDisplayAttributeFake));
+    // ... and then special handling for dimensions. Specifying this
+    // rules later means that gmock will try them first, i.e.,
+    // ordering of width/height vs. the default implementation for
+    // other queries is significant.
+    EXPECT_CALL(*mMockComposer, getDisplayAttribute(2, 1, IComposerClient::Attribute::WIDTH, _))
+            .Times(2)
+            .WillRepeatedly(DoAll(SetArgPointee<3>(400), Return(Error::NONE)));
+
+    EXPECT_CALL(*mMockComposer, getDisplayAttribute(2, 1, IComposerClient::Attribute::HEIGHT, _))
+            .Times(2)
+            .WillRepeatedly(DoAll(SetArgPointee<3>(200), Return(Error::NONE)));
+
+    // TODO: Width and height queries are not actually called. Display
+    // info returns dimensions 0x0 in display info. Why?
+
+    mMockComposer->hotplugDisplay(static_cast<Display>(2),
+                                  IComposerCallback::Connection::CONNECTED);
+
+    {
+        sp<android::IBinder> display(
+                SurfaceComposerClient::getBuiltInDisplay(ISurfaceComposer::eDisplayIdHdmi));
+        DisplayInfo info;
+        SurfaceComposerClient::getDisplayInfo(display, &info);
+        ASSERT_EQ(400u, info.w);
+        ASSERT_EQ(200u, info.h);
+
+        auto surfaceControl =
+                mComposerClient->createSurface(String8("Display Test Surface Foo"), info.w, info.h,
+                                               PIXEL_FORMAT_RGBA_8888, 0);
+        ASSERT_TRUE(surfaceControl != nullptr);
+        ASSERT_TRUE(surfaceControl->isValid());
+        fillSurfaceRGBA8(surfaceControl, BLUE);
+
+        {
+            GlobalTransactionScope gts(*mMockComposer);
+            mComposerClient->setDisplayLayerStack(display, 0);
+
+            ASSERT_EQ(NO_ERROR, surfaceControl->setLayer(INT32_MAX - 2));
+            ASSERT_EQ(NO_ERROR, surfaceControl->show());
+        }
+    }
+
+    mMockComposer->hotplugDisplay(static_cast<Display>(2),
+                                  IComposerCallback::Connection::DISCONNECTED);
+
+    mMockComposer->clearFrames();
+
+    mMockComposer->hotplugDisplay(static_cast<Display>(2),
+                                  IComposerCallback::Connection::CONNECTED);
+
+    {
+        sp<android::IBinder> display(
+                SurfaceComposerClient::getBuiltInDisplay(ISurfaceComposer::eDisplayIdHdmi));
+        DisplayInfo info;
+        SurfaceComposerClient::getDisplayInfo(display, &info);
+        ASSERT_EQ(400u, info.w);
+        ASSERT_EQ(200u, info.h);
+
+        auto surfaceControl =
+                mComposerClient->createSurface(String8("Display Test Surface Bar"), info.w, info.h,
+                                               PIXEL_FORMAT_RGBA_8888, 0);
+        ASSERT_TRUE(surfaceControl != nullptr);
+        ASSERT_TRUE(surfaceControl->isValid());
+        fillSurfaceRGBA8(surfaceControl, BLUE);
+
+        {
+            GlobalTransactionScope gts(*mMockComposer);
+            mComposerClient->setDisplayLayerStack(display, 0);
+
+            ASSERT_EQ(NO_ERROR, surfaceControl->setLayer(INT32_MAX - 2));
+            ASSERT_EQ(NO_ERROR, surfaceControl->show());
+        }
+    }
+    mMockComposer->hotplugDisplay(static_cast<Display>(2),
+                                  IComposerCallback::Connection::DISCONNECTED);
+}
+
+////////////////////////////////////////////////
+
+class TransactionTest : public ::testing::Test {
+protected:
+    // Layer array indexing constants.
+    constexpr static int BG_LAYER = 0;
+    constexpr static int FG_LAYER = 1;
+
+    static void SetUpTestCase();
+    static void TearDownTestCase();
+
+    void SetUp() override;
+    void TearDown() override;
+
+    sp<SurfaceComposerClient> mComposerClient;
+    sp<SurfaceControl> mBGSurfaceControl;
+    sp<SurfaceControl> mFGSurfaceControl;
+    std::vector<RenderState> mBaseFrame;
+    uint32_t mDisplayWidth;
+    uint32_t mDisplayHeight;
+
+    static FakeComposerClient* sFakeComposer;
+};
+
+FakeComposerClient* TransactionTest::sFakeComposer;
+
+void TransactionTest::SetUpTestCase() {
+    // TODO: See TODO comment at DisplayTest::SetUp for background on
+    // the lifetime of the FakeComposerClient.
+    sFakeComposer = new FakeComposerClient;
+    sp<ComposerClient> client = new ComposerClient(*sFakeComposer);
+    sFakeComposer->setClient(client.get());
+    sp<IComposer> fakeService = new FakeComposerService(client);
+    fakeService->registerAsService("mock");
+
+    android::hardware::ProcessState::self()->startThreadPool();
+    android::ProcessState::self()->startThreadPool();
+
+    startSurfaceFlinger();
+
+    // Fake composer wants to enable VSync injection
+    sFakeComposer->onSurfaceFlingerStart();
+}
+
+void TransactionTest::TearDownTestCase() {
+    // Fake composer needs to release SurfaceComposerClient before the stop.
+    sFakeComposer->onSurfaceFlingerStop();
+    stopSurfaceFlinger();
+    // TODO: This is deleted when the ComposerClient calls
+    // removeClient. Devise better lifetime control.
+    sFakeComposer = nullptr;
+}
+
+void TransactionTest::SetUp() {
+    ALOGI("TransactionTest::SetUp");
+    mComposerClient = new SurfaceComposerClient;
+    ASSERT_EQ(NO_ERROR, mComposerClient->initCheck());
+
+    ALOGI("TransactionTest::SetUp - display");
+    sp<android::IBinder> display(
+            SurfaceComposerClient::getBuiltInDisplay(ISurfaceComposer::eDisplayIdMain));
+    DisplayInfo info;
+    SurfaceComposerClient::getDisplayInfo(display, &info);
+
+    mDisplayWidth = info.w;
+    mDisplayHeight = info.h;
+
+    // Background surface
+    mBGSurfaceControl = mComposerClient->createSurface(String8("BG Test Surface"), mDisplayWidth,
+                                                       mDisplayHeight, PIXEL_FORMAT_RGBA_8888, 0);
+    ASSERT_TRUE(mBGSurfaceControl != nullptr);
+    ASSERT_TRUE(mBGSurfaceControl->isValid());
+    fillSurfaceRGBA8(mBGSurfaceControl, BLUE);
+
+    // Foreground surface
+    mFGSurfaceControl = mComposerClient->createSurface(String8("FG Test Surface"), 64, 64,
+                                                       PIXEL_FORMAT_RGBA_8888, 0);
+    ASSERT_TRUE(mFGSurfaceControl != nullptr);
+    ASSERT_TRUE(mFGSurfaceControl->isValid());
+
+    fillSurfaceRGBA8(mFGSurfaceControl, RED);
+
+    SurfaceComposerClient::openGlobalTransaction();
+
+    mComposerClient->setDisplayLayerStack(display, 0);
+
+    ASSERT_EQ(NO_ERROR, mBGSurfaceControl->setLayer(INT32_MAX - 2));
+    ASSERT_EQ(NO_ERROR, mBGSurfaceControl->show());
+
+    ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setLayer(INT32_MAX - 1));
+    ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setPosition(64, 64));
+    ASSERT_EQ(NO_ERROR, mFGSurfaceControl->show());
+
+    // Synchronous transaction will stop this thread, so we set up a
+    // delayed, off-thread vsync request before closing the
+    // transaction. In the test code this is usually done with
+    // GlobalTransactionScope. Leaving here in the 'vanilla' form for
+    // reference.
+    ASSERT_EQ(0, sFakeComposer->getFrameCount());
+    sFakeComposer->runVSyncAfter(1ms);
+    SurfaceComposerClient::closeGlobalTransaction(true);
+    sFakeComposer->waitUntilFrame(1);
+
+    // Reference data. This is what the HWC should see.
+    static_assert(BG_LAYER == 0 && FG_LAYER == 1, "Unexpected enum values for array indexing");
+    mBaseFrame.push_back(makeSimpleRect(0u, 0u, mDisplayWidth, mDisplayHeight));
+    mBaseFrame[BG_LAYER].mSwapCount = 1;
+    mBaseFrame.push_back(makeSimpleRect(64, 64, 64 + 64, 64 + 64));
+    mBaseFrame[FG_LAYER].mSwapCount = 1;
+
+    auto frame = sFakeComposer->getFrameRects(0);
+    ASSERT_TRUE(framesAreSame(mBaseFrame, frame));
+}
+
+void TransactionTest::TearDown() {
+    ALOGD("TransactionTest::TearDown");
+
+    mComposerClient->dispose();
+    mBGSurfaceControl = 0;
+    mFGSurfaceControl = 0;
+    mComposerClient = 0;
+
+    sFakeComposer->runVSyncAndWait();
+    mBaseFrame.clear();
+    sFakeComposer->clearFrames();
+    ASSERT_EQ(0, sFakeComposer->getFrameCount());
+
+    sp<ISurfaceComposer> sf(ComposerService::getComposerService());
+    std::vector<LayerDebugInfo> layers;
+    status_t result = sf->getLayerDebugInfo(&layers);
+    if (result != NO_ERROR) {
+        ALOGE("Failed to get layers %s %d", strerror(-result), result);
+    } else {
+        // If this fails, the test being torn down leaked layers.
+        EXPECT_EQ(0u, layers.size());
+        if (layers.size() > 0) {
+            for (auto layer = layers.begin(); layer != layers.end(); ++layer) {
+                std::cout << to_string(*layer).c_str();
+            }
+            // To ensure the next test has clean slate, will run the class
+            // tear down and setup here.
+            TearDownTestCase();
+            SetUpTestCase();
+        }
+    }
+    ALOGD("TransactionTest::TearDown - complete");
+}
+
+TEST_F(TransactionTest, LayerMove) {
+    ALOGD("TransactionTest::LayerMove");
+
+    // The scope opens and closes a global transaction and, at the
+    // same time, makes sure the SurfaceFlinger progresses one frame
+    // after the transaction closes. The results of the transaction
+    // should be available in the latest frame stored by the fake
+    // composer.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setPosition(128, 128));
+        // NOTE: No changes yet, so vsync will do nothing, HWC does not get any calls.
+        // (How to verify that? Throw in vsync and wait a 2x frame time? Separate test?)
+        //
+        // sFakeComposer->runVSyncAndWait();
+    }
+
+    fillSurfaceRGBA8(mFGSurfaceControl, GREEN);
+    sFakeComposer->runVSyncAndWait();
+
+    ASSERT_EQ(3, sFakeComposer->getFrameCount()); // Make sure the waits didn't time out and there's
+                                                  // no extra frames.
+
+    // NOTE: Frame 0 is produced in the SetUp.
+    auto frame1Ref = mBaseFrame;
+    frame1Ref[FG_LAYER].mDisplayFrame =
+            hwc_rect_t{128, 128, 128 + 64, 128 + 64}; // Top-most layer moves.
+    EXPECT_TRUE(framesAreSame(frame1Ref, sFakeComposer->getFrameRects(1)));
+
+    auto frame2Ref = frame1Ref;
+    frame2Ref[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(frame2Ref, sFakeComposer->getFrameRects(2)));
+}
+
+TEST_F(TransactionTest, LayerResize) {
+    ALOGD("TransactionTest::LayerResize");
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setSize(128, 128));
+    }
+
+    fillSurfaceRGBA8(mFGSurfaceControl, GREEN);
+    sFakeComposer->runVSyncAndWait();
+
+    ASSERT_EQ(3, sFakeComposer->getFrameCount()); // Make sure the waits didn't time out and there's
+                                                  // no extra frames.
+
+    auto frame1Ref = mBaseFrame;
+    // NOTE: The resize should not be visible for frame 1 as there's no buffer with new size posted.
+    EXPECT_TRUE(framesAreSame(frame1Ref, sFakeComposer->getFrameRects(1)));
+
+    auto frame2Ref = frame1Ref;
+    frame2Ref[FG_LAYER].mSwapCount++;
+    frame2Ref[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 128, 64 + 128};
+    frame2Ref[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 128.f, 128.f};
+    EXPECT_TRUE(framesAreSame(frame2Ref, sFakeComposer->getFrameRects(2)));
+}
+
+TEST_F(TransactionTest, LayerCrop) {
+    // TODO: Add scaling to confirm that crop happens in buffer space?
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        Rect cropRect(16, 16, 32, 32);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setCrop(cropRect));
+    }
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{16.f, 16.f, 32.f, 32.f};
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{64 + 16, 64 + 16, 64 + 32, 64 + 32};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerFinalCrop) {
+    // TODO: Add scaling to confirm that crop happens in display space?
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        Rect cropRect(32, 32, 32 + 64, 32 + 64);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setFinalCrop(cropRect));
+    }
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+
+    // In display space we are cropping with [32, 32, 96, 96] against display rect
+    // [64, 64, 128, 128]. Should yield display rect [64, 64, 96, 96]
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 32.f, 32.f};
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 32, 64 + 32};
+
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerFinalCropEmpty) {
+    // TODO: Add scaling to confirm that crop happens in display space?
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        Rect cropRect(16, 16, 32, 32);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setFinalCrop(cropRect));
+    }
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+
+    // In display space we are cropping with [16, 16, 32, 32] against display rect
+    // [64, 64, 128, 128]. The intersection is empty and only the background layer is composited.
+    std::vector<RenderState> referenceFrame(1);
+    referenceFrame[BG_LAYER] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerSetLayer) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setLayer(INT_MAX - 3));
+    }
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+
+    // The layers will switch order, but both are rendered because the background layer is
+    // transparent (RGBA8888).
+    std::vector<RenderState> referenceFrame(2);
+    referenceFrame[0] = mBaseFrame[FG_LAYER];
+    referenceFrame[1] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerSetLayerOpaque) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setLayer(INT_MAX - 3));
+        ASSERT_EQ(NO_ERROR,
+                  mBGSurfaceControl->setFlags(layer_state_t::eLayerOpaque,
+                                              layer_state_t::eLayerOpaque));
+    }
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+
+    // The former foreground layer is now covered with opaque layer - it should have disappeared
+    std::vector<RenderState> referenceFrame(1);
+    referenceFrame[BG_LAYER] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, SetLayerStack) {
+    ALOGD("TransactionTest::SetLayerStack");
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setLayerStack(1));
+    }
+
+    // Foreground layer should have disappeared.
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+    std::vector<RenderState> refFrame(1);
+    refFrame[BG_LAYER] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(refFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerShowHide) {
+    ALOGD("TransactionTest::LayerShowHide");
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->hide());
+    }
+
+    // Foreground layer should have disappeared.
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+    std::vector<RenderState> refFrame(1);
+    refFrame[BG_LAYER] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(refFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->show());
+    }
+
+    // Foreground layer should be back
+    ASSERT_EQ(3, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerSetAlpha) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setAlpha(0.75f));
+    }
+
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mPlaneAlpha = 0.75f;
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerSetFlags) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR,
+                  mFGSurfaceControl->setFlags(layer_state_t::eLayerHidden,
+                                              layer_state_t::eLayerHidden));
+    }
+
+    // Foreground layer should have disappeared.
+    ASSERT_EQ(2, sFakeComposer->getFrameCount());
+    std::vector<RenderState> refFrame(1);
+    refFrame[BG_LAYER] = mBaseFrame[BG_LAYER];
+    EXPECT_TRUE(framesAreSame(refFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, LayerSetMatrix) {
+    struct matrixTestData {
+        float matrix[4];
+        hwc_transform_t expectedTransform;
+        hwc_rect_t expectedDisplayFrame;
+    };
+
+    // The matrix operates on the display frame and is applied before
+    // the position is added. So, the foreground layer rect is (0, 0,
+    // 64, 64) is first transformed, potentially yielding negative
+    // coordinates and then the position (64, 64) is added yielding
+    // the final on-screen rectangles given.
+
+    const matrixTestData MATRIX_TESTS[7] = // clang-format off
+            {{{-1.f, 0.f, 0.f, 1.f},    HWC_TRANSFORM_FLIP_H,           {0, 64, 64, 128}},
+             {{1.f, 0.f, 0.f, -1.f},    HWC_TRANSFORM_FLIP_V,           {64, 0, 128, 64}},
+             {{0.f, 1.f, -1.f, 0.f},    HWC_TRANSFORM_ROT_90,           {0, 64, 64, 128}},
+             {{-1.f, 0.f, 0.f, -1.f},   HWC_TRANSFORM_ROT_180,          {0, 0, 64, 64}},
+             {{0.f, -1.f, 1.f, 0.f},    HWC_TRANSFORM_ROT_270,          {64, 0, 128, 64}},
+             {{0.f, 1.f, 1.f, 0.f},     HWC_TRANSFORM_FLIP_H_ROT_90,    {64, 64, 128, 128}},
+             {{0.f, 1.f, 1.f, 0.f},     HWC_TRANSFORM_FLIP_V_ROT_90,    {64, 64, 128, 128}}};
+    // clang-format on
+    constexpr int TEST_COUNT = sizeof(MATRIX_TESTS)/sizeof(matrixTestData);
+
+    for (int i = 0; i < TEST_COUNT; i++) {
+        // TODO: How to leverage the HWC2 stringifiers?
+        const matrixTestData& xform = MATRIX_TESTS[i];
+        SCOPED_TRACE(i);
+        {
+            GlobalTransactionScope gts(*sFakeComposer);
+            ASSERT_EQ(NO_ERROR,
+                      mFGSurfaceControl->setMatrix(xform.matrix[0], xform.matrix[1],
+                                                   xform.matrix[2], xform.matrix[3]));
+        }
+
+        auto referenceFrame = mBaseFrame;
+        referenceFrame[FG_LAYER].mTransform = xform.expectedTransform;
+        referenceFrame[FG_LAYER].mDisplayFrame = xform.expectedDisplayFrame;
+
+        EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+    }
+}
+
+#if 0
+TEST_F(TransactionTest, LayerSetMatrix2) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        // TODO: PLEASE SPEC THE FUNCTION!
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setMatrix(0.11f, 0.123f,
+                                                         -2.33f, 0.22f));
+    }
+    auto referenceFrame = mBaseFrame;
+    // TODO: Is this correct for sure?
+    //referenceFrame[FG_LAYER].mTransform = HWC_TRANSFORM_FLIP_V & HWC_TRANSFORM_ROT_90;
+
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+#endif
+
+TEST_F(TransactionTest, DeferredTransaction) {
+    // Synchronization surface
+    constexpr static int SYNC_LAYER = 2;
+    auto syncSurfaceControl = mComposerClient->createSurface(String8("Sync Test Surface"), 1, 1,
+                                                             PIXEL_FORMAT_RGBA_8888, 0);
+    ASSERT_TRUE(syncSurfaceControl != nullptr);
+    ASSERT_TRUE(syncSurfaceControl->isValid());
+
+    fillSurfaceRGBA8(syncSurfaceControl, DARK_GRAY);
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, syncSurfaceControl->setLayer(INT32_MAX - 1));
+        ASSERT_EQ(NO_ERROR, syncSurfaceControl->setPosition(mDisplayWidth - 2, mDisplayHeight - 2));
+        ASSERT_EQ(NO_ERROR, syncSurfaceControl->show());
+    }
+    auto referenceFrame = mBaseFrame;
+    referenceFrame.push_back(makeSimpleRect(mDisplayWidth - 2, mDisplayHeight - 2,
+                                            mDisplayWidth - 1, mDisplayHeight - 1));
+    referenceFrame[SYNC_LAYER].mSwapCount = 1;
+    EXPECT_EQ(2, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    // set up two deferred transactions on different frames - these should not yield composited
+    // frames
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setAlpha(0.75));
+        mFGSurfaceControl
+                ->deferTransactionUntil(syncSurfaceControl->getHandle(),
+                                        syncSurfaceControl->getSurface()->getNextFrameNumber());
+    }
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setPosition(128, 128));
+        mFGSurfaceControl
+                ->deferTransactionUntil(syncSurfaceControl->getHandle(),
+                                        syncSurfaceControl->getSurface()->getNextFrameNumber() + 1);
+    }
+    EXPECT_EQ(4, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    // should trigger the first deferred transaction, but not the second one
+    fillSurfaceRGBA8(syncSurfaceControl, DARK_GRAY);
+    sFakeComposer->runVSyncAndWait();
+    EXPECT_EQ(5, sFakeComposer->getFrameCount());
+
+    referenceFrame[FG_LAYER].mPlaneAlpha = 0.75f;
+    referenceFrame[SYNC_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    // should show up immediately since it's not deferred
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setAlpha(1.0));
+    }
+    referenceFrame[FG_LAYER].mPlaneAlpha = 1.f;
+    EXPECT_EQ(6, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    // trigger the second deferred transaction
+    fillSurfaceRGBA8(syncSurfaceControl, DARK_GRAY);
+    sFakeComposer->runVSyncAndWait();
+    // TODO: Compute from layer size?
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{128, 128, 128 + 64, 128 + 64};
+    referenceFrame[SYNC_LAYER].mSwapCount++;
+    EXPECT_EQ(7, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(TransactionTest, SetRelativeLayer) {
+    constexpr int RELATIVE_LAYER = 2;
+    auto relativeSurfaceControl = mComposerClient->createSurface(String8("Test Surface"), 64, 64,
+                                                                 PIXEL_FORMAT_RGBA_8888, 0);
+    fillSurfaceRGBA8(relativeSurfaceControl, LIGHT_RED);
+
+    // Now we stack the surface above the foreground surface and make sure it is visible.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        relativeSurfaceControl->setPosition(64, 64);
+        relativeSurfaceControl->show();
+        relativeSurfaceControl->setRelativeLayer(mFGSurfaceControl->getHandle(), 1);
+    }
+    auto referenceFrame = mBaseFrame;
+    // NOTE: All three layers will be visible as the surfaces are
+    // transparent because of the RGBA format.
+    referenceFrame.push_back(makeSimpleRect(64, 64, 64 + 64, 64 + 64));
+    referenceFrame[RELATIVE_LAYER].mSwapCount = 1;
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    // A call to setLayer will override a call to setRelativeLayer
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        relativeSurfaceControl->setLayer(0);
+    }
+
+    // Previous top layer will now appear at the bottom.
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2.insert(referenceFrame2.begin(), referenceFrame[RELATIVE_LAYER]);
+    EXPECT_EQ(3, sFakeComposer->getFrameCount());
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+class ChildLayerTest : public TransactionTest {
+protected:
+    constexpr static int CHILD_LAYER = 2;
+
+    void SetUp() override {
+        TransactionTest::SetUp();
+        mChild = mComposerClient->createSurface(String8("Child surface"), 10, 10,
+                                                PIXEL_FORMAT_RGBA_8888, 0, mFGSurfaceControl.get());
+        fillSurfaceRGBA8(mChild, LIGHT_GRAY);
+
+        sFakeComposer->runVSyncAndWait();
+        mBaseFrame.push_back(makeSimpleRect(64, 64, 64 + 10, 64 + 10));
+        mBaseFrame[CHILD_LAYER].mSwapCount = 1;
+        ASSERT_EQ(2, sFakeComposer->getFrameCount());
+        ASSERT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+    }
+    void TearDown() override {
+        mChild = 0;
+        TransactionTest::TearDown();
+    }
+
+    sp<SurfaceControl> mChild;
+};
+
+TEST_F(ChildLayerTest, Positioning) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(10, 10);
+        // Move to the same position as in the original setup.
+        mFGSurfaceControl->setPosition(64, 64);
+    }
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 64, 64 + 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame =
+            hwc_rect_t{64 + 10, 64 + 10, 64 + 10 + 10, 64 + 10 + 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setPosition(0, 0));
+    }
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 0 + 64, 0 + 64};
+    referenceFrame2[CHILD_LAYER].mDisplayFrame =
+            hwc_rect_t{0 + 10, 0 + 10, 0 + 10 + 10, 0 + 10 + 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, Cropping) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(0, 0);
+        mFGSurfaceControl->setPosition(0, 0);
+        mFGSurfaceControl->setCrop(Rect(0, 0, 5, 5));
+    }
+    // NOTE: The foreground surface would be occluded by the child
+    // now, but is included in the stack because the child is
+    // transparent.
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 0 + 5, 0 + 5};
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 5.f, 5.f};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 0 + 5, 0 + 5};
+    referenceFrame[CHILD_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 5.f, 5.f};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, FinalCropping) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(0, 0);
+        mFGSurfaceControl->setPosition(0, 0);
+        mFGSurfaceControl->setFinalCrop(Rect(0, 0, 5, 5));
+    }
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 0 + 5, 0 + 5};
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 5.f, 5.f};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 0 + 5, 0 + 5};
+    referenceFrame[CHILD_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 5.f, 5.f};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, Constraints) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mFGSurfaceControl->setPosition(0, 0);
+        mChild->setPosition(63, 63);
+    }
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 64, 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{63, 63, 64, 64};
+    referenceFrame[CHILD_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 1.f, 1.f};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, Scaling) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setPosition(0, 0);
+    }
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 64, 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 10, 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setMatrix(2.0, 0, 0, 2.0);
+    }
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 128, 128};
+    referenceFrame2[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 20, 20};
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, LayerAlpha) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(0, 0);
+        mFGSurfaceControl->setPosition(0, 0);
+        ASSERT_EQ(NO_ERROR, mChild->setAlpha(0.5));
+    }
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 64, 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 10, 10};
+    referenceFrame[CHILD_LAYER].mPlaneAlpha = 0.5f;
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        ASSERT_EQ(NO_ERROR, mFGSurfaceControl->setAlpha(0.5));
+    }
+
+    auto referenceFrame2 = referenceFrame;
+    referenceFrame2[FG_LAYER].mPlaneAlpha = 0.5f;
+    referenceFrame2[CHILD_LAYER].mPlaneAlpha = 0.25f;
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, ReparentChildren) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(10, 10);
+        mFGSurfaceControl->setPosition(64, 64);
+    }
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 64, 64 + 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame =
+            hwc_rect_t{64 + 10, 64 + 10, 64 + 10 + 10, 64 + 10 + 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->reparentChildren(mBGSurfaceControl->getHandle());
+    }
+
+    auto referenceFrame2 = referenceFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 64, 64 + 64};
+    referenceFrame2[CHILD_LAYER].mDisplayFrame = hwc_rect_t{10, 10, 10 + 10, 10 + 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, DetachChildren) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(10, 10);
+        mFGSurfaceControl->setPosition(64, 64);
+    }
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 64, 64 + 64};
+    referenceFrame[CHILD_LAYER].mDisplayFrame =
+            hwc_rect_t{64 + 10, 64 + 10, 64 + 10 + 10, 64 + 10 + 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->detachChildren();
+    }
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->hide();
+    }
+
+    // Nothing should have changed. The child control becomes a no-op
+    // zombie on detach. See comments for detachChildren in the
+    // SurfaceControl.h file.
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, InheritNonTransformScalingFromParent) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(0, 0);
+        mFGSurfaceControl->setPosition(0, 0);
+    }
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setOverrideScalingMode(NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW);
+        // We cause scaling by 2.
+        mFGSurfaceControl->setSize(128, 128);
+    }
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 128, 128};
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 64.f, 64.f};
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 20, 20};
+    referenceFrame[CHILD_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 10.f, 10.f};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+// Regression test for b/37673612
+TEST_F(ChildLayerTest, ChildrenWithParentBufferTransform) {
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->show();
+        mChild->setPosition(0, 0);
+        mFGSurfaceControl->setPosition(0, 0);
+    }
+
+    // We set things up as in b/37673612 so that there is a mismatch between the buffer size and
+    // the WM specified state size.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 64);
+    }
+
+    sp<Surface> s = mFGSurfaceControl->getSurface();
+    auto anw = static_cast<ANativeWindow*>(s.get());
+    native_window_set_buffers_transform(anw, NATIVE_WINDOW_TRANSFORM_ROT_90);
+    native_window_set_buffers_dimensions(anw, 64, 128);
+    fillSurfaceRGBA8(mFGSurfaceControl, RED);
+    sFakeComposer->runVSyncAndWait();
+
+    // The child should still be in the same place and not have any strange scaling as in
+    // b/37673612.
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 128, 64};
+    referenceFrame[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 64.f, 128.f};
+    referenceFrame[FG_LAYER].mSwapCount++;
+    referenceFrame[CHILD_LAYER].mDisplayFrame = hwc_rect_t{0, 0, 10, 10};
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(ChildLayerTest, Bug36858924) {
+    // Destroy the child layer
+    mChild.clear();
+
+    // Now recreate it as hidden
+    mChild = mComposerClient->createSurface(String8("Child surface"), 10, 10,
+                                            PIXEL_FORMAT_RGBA_8888, ISurfaceComposerClient::eHidden,
+                                            mFGSurfaceControl.get());
+
+    // Show the child layer in a deferred transaction
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mChild->deferTransactionUntil(mFGSurfaceControl->getHandle(),
+                                      mFGSurfaceControl->getSurface()->getNextFrameNumber());
+        mChild->show();
+    }
+
+    // Render the foreground surface a few times
+    //
+    // Prior to the bugfix for b/36858924, this would usually hang while trying to fill the third
+    // frame because SurfaceFlinger would never process the deferred transaction and would therefore
+    // never acquire/release the first buffer
+    ALOGI("Filling 1");
+    fillSurfaceRGBA8(mFGSurfaceControl, GREEN);
+    sFakeComposer->runVSyncAndWait();
+    ALOGI("Filling 2");
+    fillSurfaceRGBA8(mFGSurfaceControl, BLUE);
+    sFakeComposer->runVSyncAndWait();
+    ALOGI("Filling 3");
+    fillSurfaceRGBA8(mFGSurfaceControl, RED);
+    sFakeComposer->runVSyncAndWait();
+    ALOGI("Filling 4");
+    fillSurfaceRGBA8(mFGSurfaceControl, GREEN);
+    sFakeComposer->runVSyncAndWait();
+}
+
+class LatchingTest : public TransactionTest {
+protected:
+    void lockAndFillFGBuffer() { fillSurfaceRGBA8(mFGSurfaceControl, RED, false); }
+
+    void unlockFGBuffer() {
+        sp<Surface> s = mFGSurfaceControl->getSurface();
+        ASSERT_EQ(NO_ERROR, s->unlockAndPost());
+        sFakeComposer->runVSyncAndWait();
+    }
+
+    void completeFGResize() {
+        fillSurfaceRGBA8(mFGSurfaceControl, RED);
+        sFakeComposer->runVSyncAndWait();
+    }
+    void restoreInitialState() {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(64, 64);
+        mFGSurfaceControl->setPosition(64, 64);
+        mFGSurfaceControl->setCrop(Rect(0, 0, 64, 64));
+        mFGSurfaceControl->setFinalCrop(Rect(0, 0, -1, -1));
+    }
+};
+
+TEST_F(LatchingTest, SurfacePositionLatching) {
+    // By default position can be updated even while
+    // a resize is pending.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(32, 32);
+        mFGSurfaceControl->setPosition(100, 100);
+    }
+
+    // The size should not have updated as we have not provided a new buffer.
+    auto referenceFrame1 = mBaseFrame;
+    referenceFrame1[FG_LAYER].mDisplayFrame = hwc_rect_t{100, 100, 100 + 64, 100 + 64};
+    EXPECT_TRUE(framesAreSame(referenceFrame1, sFakeComposer->getLatestFrame()));
+
+    restoreInitialState();
+
+    // Now we repeat with setGeometryAppliesWithResize
+    // and verify the position DOESN'T latch.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setGeometryAppliesWithResize();
+        mFGSurfaceControl->setSize(32, 32);
+        mFGSurfaceControl->setPosition(100, 100);
+    }
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+
+    completeFGResize();
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{100, 100, 100 + 32, 100 + 32};
+    referenceFrame2[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 32.f, 32.f};
+    referenceFrame2[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(LatchingTest, CropLatching) {
+    // Normally the crop applies immediately even while a resize is pending.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setCrop(Rect(0, 0, 63, 63));
+    }
+
+    auto referenceFrame1 = mBaseFrame;
+    referenceFrame1[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 63, 64 + 63};
+    referenceFrame1[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 63.f, 63.f};
+    EXPECT_TRUE(framesAreSame(referenceFrame1, sFakeComposer->getLatestFrame()));
+
+    restoreInitialState();
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setGeometryAppliesWithResize();
+        mFGSurfaceControl->setCrop(Rect(0, 0, 63, 63));
+    }
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+
+    completeFGResize();
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 64 + 63, 64 + 63};
+    referenceFrame2[FG_LAYER].mSourceCrop = hwc_frect_t{0.f, 0.f, 63.f, 63.f};
+    referenceFrame2[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(LatchingTest, FinalCropLatching) {
+    // Normally the crop applies immediately even while a resize is pending.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setFinalCrop(Rect(64, 64, 127, 127));
+    }
+
+    auto referenceFrame1 = mBaseFrame;
+    referenceFrame1[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 127, 127};
+    referenceFrame1[FG_LAYER].mSourceCrop =
+            hwc_frect_t{0.f, 0.f, static_cast<float>(127 - 64), static_cast<float>(127 - 64)};
+    EXPECT_TRUE(framesAreSame(referenceFrame1, sFakeComposer->getLatestFrame()));
+
+    restoreInitialState();
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setGeometryAppliesWithResize();
+        mFGSurfaceControl->setFinalCrop(Rect(64, 64, 127, 127));
+    }
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+
+    completeFGResize();
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 127, 127};
+    referenceFrame2[FG_LAYER].mSourceCrop =
+            hwc_frect_t{0.f, 0.f, static_cast<float>(127 - 64), static_cast<float>(127 - 64)};
+    referenceFrame2[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+}
+
+// In this test we ensure that setGeometryAppliesWithResize actually demands
+// a buffer of the new size, and not just any size.
+TEST_F(LatchingTest, FinalCropLatchingBufferOldSize) {
+    // Normally the crop applies immediately even while a resize is pending.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setFinalCrop(Rect(64, 64, 127, 127));
+    }
+
+    auto referenceFrame1 = mBaseFrame;
+    referenceFrame1[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 127, 127};
+    referenceFrame1[FG_LAYER].mSourceCrop =
+            hwc_frect_t{0.f, 0.f, static_cast<float>(127 - 64), static_cast<float>(127 - 64)};
+    EXPECT_TRUE(framesAreSame(referenceFrame1, sFakeComposer->getLatestFrame()));
+
+    restoreInitialState();
+
+    // In order to prepare to submit a buffer at the wrong size, we acquire it prior to
+    // initiating the resize.
+    lockAndFillFGBuffer();
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setGeometryAppliesWithResize();
+        mFGSurfaceControl->setFinalCrop(Rect(64, 64, 127, 127));
+    }
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+
+    // We now submit our old buffer, at the old size, and ensure it doesn't
+    // trigger geometry latching.
+    unlockFGBuffer();
+
+    auto referenceFrame2 = mBaseFrame;
+    referenceFrame2[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame2, sFakeComposer->getLatestFrame()));
+
+    completeFGResize();
+    auto referenceFrame3 = referenceFrame2;
+    referenceFrame3[FG_LAYER].mDisplayFrame = hwc_rect_t{64, 64, 127, 127};
+    referenceFrame3[FG_LAYER].mSourceCrop =
+            hwc_frect_t{0.f, 0.f, static_cast<float>(127 - 64), static_cast<float>(127 - 64)};
+    referenceFrame3[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame3, sFakeComposer->getLatestFrame()));
+}
+
+TEST_F(LatchingTest, FinalCropLatchingRegressionForb37531386) {
+    // In this scenario, we attempt to set the final crop a second time while the resize
+    // is still pending, and ensure we are successful. Success meaning the second crop
+    // is the one which eventually latches and not the first.
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setSize(128, 128);
+        mFGSurfaceControl->setGeometryAppliesWithResize();
+        mFGSurfaceControl->setFinalCrop(Rect(64, 64, 127, 127));
+    }
+
+    {
+        GlobalTransactionScope gts(*sFakeComposer);
+        mFGSurfaceControl->setFinalCrop(Rect(0, 0, -1, -1));
+    }
+    EXPECT_TRUE(framesAreSame(mBaseFrame, sFakeComposer->getLatestFrame()));
+
+    completeFGResize();
+
+    auto referenceFrame = mBaseFrame;
+    referenceFrame[FG_LAYER].mSwapCount++;
+    EXPECT_TRUE(framesAreSame(referenceFrame, sFakeComposer->getLatestFrame()));
+}
+
+} // namespace
+
+int main(int argc, char** argv) {
+    ::testing::InitGoogleTest(&argc, argv);
+
+    sftest::FakeHwcEnvironment* fakeEnvironment = new sftest::FakeHwcEnvironment;
+    ::testing::AddGlobalTestEnvironment(fakeEnvironment);
+    ::testing::InitGoogleMock(&argc, argv);
+    return RUN_ALL_TESTS();
+}