diff --git a/libs/utils/tests/Android.mk b/libs/utils/tests/Android.mk
new file mode 100644
index 0000000..45e8061
--- /dev/null
+++ b/libs/utils/tests/Android.mk
@@ -0,0 +1,33 @@
+# Build the unit tests.
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+test_src_files := \
+	PollLoop_test.cpp
+
+LOCAL_SHARED_LIBRARIES := \
+	libz \
+	liblog \
+	libcutils \
+	libutils \
+	libstlport
+
+LOCAL_STATIC_LIBRARIES := \
+	libgtest \
+	libgtest_main
+
+LOCAL_C_INCLUDES := \
+    external/zlib \
+    external/icu4c/common \
+    bionic \
+    bionic/libstdc++/include \
+    external/gtest/include \
+    external/stlport/stlport
+
+LOCAL_MODULE_TAGS := eng tests
+
+$(foreach file,$(test_src_files), \
+    $(eval LOCAL_SRC_FILES := $(file)) \
+    $(eval LOCAL_MODULE := $(notdir $(file:%.cpp=%))) \
+    $(eval include $(BUILD_EXECUTABLE)) \
+)
diff --git a/libs/utils/tests/PollLoop_test.cpp b/libs/utils/tests/PollLoop_test.cpp
new file mode 100644
index 0000000..6c719c8
--- /dev/null
+++ b/libs/utils/tests/PollLoop_test.cpp
@@ -0,0 +1,398 @@
+//
+// Copyright 2010 The Android Open Source Project
+//
+
+#include <utils/PollLoop.h>
+#include <utils/Timers.h>
+#include <utils/StopWatch.h>
+#include <gtest/gtest.h>
+#include <unistd.h>
+#include <time.h>
+
+#include "TestHelpers.h"
+
+// # of milliseconds to fudge stopwatch measurements
+#define TIMING_TOLERANCE_MS 25
+
+namespace android {
+
+class Pipe {
+public:
+    int sendFd;
+    int receiveFd;
+
+    Pipe() {
+        int fds[2];
+        ::pipe(fds);
+
+        receiveFd = fds[0];
+        sendFd = fds[1];
+    }
+
+    ~Pipe() {
+        ::close(sendFd);
+        ::close(receiveFd);
+    }
+
+    bool writeSignal() {
+        return ::write(sendFd, "*", 1) == 1;
+    }
+
+    bool readSignal() {
+        char buf[1];
+        return ::read(receiveFd, buf, 1) == 1;
+    }
+};
+
+class DelayedWake : public DelayedTask {
+    sp<PollLoop> mPollLoop;
+
+public:
+    DelayedWake(int delayMillis, const sp<PollLoop> pollLoop) :
+        DelayedTask(delayMillis), mPollLoop(pollLoop) {
+    }
+
+protected:
+    virtual void doTask() {
+        mPollLoop->wake();
+    }
+};
+
+class DelayedWriteSignal : public DelayedTask {
+    Pipe* mPipe;
+
+public:
+    DelayedWriteSignal(int delayMillis, Pipe* pipe) :
+        DelayedTask(delayMillis), mPipe(pipe) {
+    }
+
+protected:
+    virtual void doTask() {
+        mPipe->writeSignal();
+    }
+};
+
+class CallbackHandler {
+public:
+    void setCallback(const sp<PollLoop>& pollLoop, int fd, int events) {
+        pollLoop->setCallback(fd, events, staticHandler, this);
+    }
+
+protected:
+    virtual ~CallbackHandler() { }
+
+    virtual bool handler(int fd, int events) = 0;
+
+private:
+    static bool staticHandler(int fd, int events, void* data) {
+        return static_cast<CallbackHandler*>(data)->handler(fd, events);
+    }
+};
+
+class StubCallbackHandler : public CallbackHandler {
+public:
+    bool nextResult;
+    int callbackCount;
+
+    int fd;
+    int events;
+
+    StubCallbackHandler(bool nextResult) : nextResult(nextResult),
+            callbackCount(0), fd(-1), events(-1) {
+    }
+
+protected:
+    virtual bool handler(int fd, int events) {
+        callbackCount += 1;
+        this->fd = fd;
+        this->events = events;
+        return nextResult;
+    }
+};
+
+class PollLoopTest : public testing::Test {
+protected:
+    sp<PollLoop> mPollLoop;
+
+    virtual void SetUp() {
+        mPollLoop = new PollLoop();
+    }
+
+    virtual void TearDown() {
+        mPollLoop.clear();
+    }
+};
+
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndNotAwoken_WaitsForTimeoutAndReturnsFalse) {
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndAwokenBeforeWaiting_ImmediatelyReturnsTrue) {
+    mPollLoop->wake();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. zero because wake() was called before waiting";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because loop was awoken";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndAwokenWhileWaiting_PromptlyReturnsTrue) {
+    sp<DelayedWake> delayedWake = new DelayedWake(100, mPollLoop);
+    delayedWake->run();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal wake delay";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because loop was awoken";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndNoRegisteredFDs_ImmediatelyReturnsFalse) {
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndNoSignalledFDs_ImmediatelyReturnsFalse) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not have been invoked because FD was not signalled";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenZeroTimeoutAndSignalledFD_ImmediatelyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    ASSERT_TRUE(pipe.writeSignal());
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndNoSignalledFDs_WaitsForTimeoutAndReturnsFalse) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not have been invoked because FD was not signalled";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndSignalledFDBeforeWaiting_ImmediatelyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    pipe.writeSignal();
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should be approx. zero";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenNonZeroTimeoutAndSignalledFDWhileWaiting_PromptlyInvokesCallbackAndReturnsTrue) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+    sp<DelayedWriteSignal> delayedWriteSignal = new DelayedWriteSignal(100, & pipe);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    delayedWriteSignal->run();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(1000);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal signal delay";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked exactly once";
+    EXPECT_EQ(pipe.receiveFd, handler.fd)
+            << "callback should have received pipe fd as parameter";
+    EXPECT_EQ(POLL_IN, handler.events)
+            << "callback should have received POLL_IN as events";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackAddedThenRemoved_CallbackShouldNotBeInvoked) {
+    Pipe pipe;
+    StubCallbackHandler handler(true);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    pipe.writeSignal(); // would cause FD to be considered signalled
+    mPollLoop->removeCallback(pipe.receiveFd);
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(100, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal timeout because FD was no longer registered";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(0, handler.callbackCount)
+            << "callback should not be invoked";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackReturnsFalse_CallbackShouldNotBeInvokedAgainLater) {
+    Pipe pipe;
+    StubCallbackHandler handler(false);
+
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    // First loop: Callback is registered and FD is signalled.
+    pipe.writeSignal();
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(0);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal zero because FD was already signalled";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should be invoked";
+
+    // Second loop: Callback is no longer registered and FD is signalled.
+    pipe.writeSignal();
+
+    stopWatch.reset();
+    result = mPollLoop->pollOnce(0);
+    elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. equal zero because timeout was zero";
+    EXPECT_FALSE(result)
+            << "pollOnce result should be false because timeout occurred";
+    EXPECT_EQ(1, handler.callbackCount)
+            << "callback should not be invoked this time";
+}
+
+TEST_F(PollLoopTest, RemoveCallback_WhenCallbackNotAdded_ReturnsFalse) {
+    bool result = mPollLoop->removeCallback(1);
+
+    EXPECT_FALSE(result)
+            << "removeCallback should return false because FD not registered";
+}
+
+TEST_F(PollLoopTest, RemoveCallback_WhenCallbackAddedThenRemovedTwice_ReturnsTrueFirstTimeAndReturnsFalseSecondTime) {
+    Pipe pipe;
+    StubCallbackHandler handler(false);
+    handler.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+
+    // First time.
+    bool result = mPollLoop->removeCallback(pipe.receiveFd);
+
+    EXPECT_TRUE(result)
+            << "removeCallback should return true first time because FD was registered";
+
+    // Second time.
+    result = mPollLoop->removeCallback(pipe.receiveFd);
+
+    EXPECT_FALSE(result)
+            << "removeCallback should return false second time because FD was no longer registered";
+}
+
+TEST_F(PollLoopTest, PollOnce_WhenCallbackAddedTwice_OnlySecondCallbackShouldBeInvoked) {
+    Pipe pipe;
+    StubCallbackHandler handler1(true);
+    StubCallbackHandler handler2(true);
+
+    handler1.setCallback(mPollLoop, pipe.receiveFd, POLL_IN);
+    handler2.setCallback(mPollLoop, pipe.receiveFd, POLL_IN); // replace it
+    pipe.writeSignal(); // would cause FD to be considered signalled
+
+    StopWatch stopWatch("pollOnce");
+    bool result = mPollLoop->pollOnce(100);
+    int32_t elapsedMillis = ns2ms(stopWatch.elapsedTime());
+
+    ASSERT_TRUE(pipe.readSignal())
+            << "signal should actually have been written";
+    EXPECT_NEAR(0, elapsedMillis, TIMING_TOLERANCE_MS)
+            << "elapsed time should approx. zero because FD was already signalled";
+    EXPECT_TRUE(result)
+            << "pollOnce result should be true because FD was signalled";
+    EXPECT_EQ(0, handler1.callbackCount)
+            << "original handler callback should not be invoked because it was replaced";
+    EXPECT_EQ(1, handler2.callbackCount)
+            << "replacement handler callback should be invoked";
+}
+
+
+} // namespace android
diff --git a/libs/utils/tests/TestHelpers.h b/libs/utils/tests/TestHelpers.h
new file mode 100644
index 0000000..e55af3c
--- /dev/null
+++ b/libs/utils/tests/TestHelpers.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2010 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.
+ */
+
+#ifndef TESTHELPERS_H
+#define TESTHELPERS_H
+
+#include <utils/threads.h>
+
+namespace android {
+
+class DelayedTask : public Thread {
+    int mDelayMillis;
+
+public:
+    DelayedTask(int delayMillis) : mDelayMillis(delayMillis) { }
+
+protected:
+    virtual ~DelayedTask() { }
+
+    virtual void doTask() = 0;
+
+    virtual bool threadLoop() {
+        usleep(mDelayMillis * 1000);
+        doTask();
+        return false;
+    }
+};
+
+} // namespace android
+
+#endif // TESTHELPERS_H