diff --git a/CMakeLists.txt b/CMakeLists.txt
index e0f61d2..2adefa4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -77,12 +77,25 @@ target_link_libraries(sled PUBLIC rpc_core fmt marl)
 if(SLED_BUILD_BENCHMARK)
     find_package(benchmark REQUIRED)
 
-    add_executable(sled_benchmark benchmark/strings/base64_benchmark.cc)
+    add_executable(sled_benchmark "src/system/fiber/fiber_bench.cc")
     target_link_libraries(sled_benchmark PRIVATE sled benchmark::benchmark
                                                benchmark::benchmark_main)
 endif(SLED_BUILD_BENCHMARK)
 
 if(SLED_BUILD_TESTS)
-    find_package(gtest REQUIRED)
-    add_executable(sled_tests "")
+    include(FetchContent)
+    FetchContent_Declare(
+      googletest
+      URL https://github.com/google/googletest/archive/03597a01ee50ed33e9dfd640b249b4be3799d395.zip
+    )
+    FetchContent_MakeAvailable(googletest)
+    add_executable(sled_tests 
+        src/filesystem/path_test.cc
+        src/strings/base64_test.cc
+        src/cleanup_test.cc
+        src/status_or_test.cc
+        src/system/fiber/fiber_test.cc
+        )
+    target_link_libraries(sled_tests PRIVATE sled GTest::gtest GTest::gtest_main)
+    add_test(NAME sled_tests COMMAND sled_tests)
 endif(SLED_BUILD_TESTS)
diff --git a/benchmark/strings/base64_benchmark.cc b/benchmark/strings/base64_benchmark.cc
deleted file mode 100644
index c9e2740..0000000
--- a/benchmark/strings/base64_benchmark.cc
+++ /dev/null
@@ -1,59 +0,0 @@
-#include <benchmark/benchmark.h>
-#include <sled/random.h>
-#include <sled/strings/base64.h>
-#include <sstream>
-
-struct strings {};
-
-static std::string
-AllocRandomString(sled::Random &random, int len)
-{
-    std::stringstream ss;
-    for (int i = len; i > 0; i--) { ss << random.Rand<char>(); }
-    return ss.str();
-}
-
-void
-BenchmarkBase64Encode(benchmark::State &state)
-{
-    state.PauseTiming();
-    sled::Random random(2393);
-    std::vector<std::string> test_data;
-    for (int i = 0; i < state.range(0); i++) {
-        test_data.emplace_back(AllocRandomString(random, state.range(1)));
-    }
-
-    state.ResumeTiming();
-    for (int i = 0; i < state.range(2); i++) {
-        for (const auto &str : test_data) {
-            auto base64 = sled::Base64::Encode(str);
-        }
-    }
-}
-
-std::string
-uint2str(unsigned int num)
-{
-    std::ostringstream oss;
-    oss << num;
-    return oss.str();
-}
-
-void
-test(benchmark::State &state)
-{
-    for (int i = 0; i < 1000000; i++) (void) uint2str(i);
-    state.end();
-}
-
-BENCHMARK(test);
-/*
-BENCHMARK(BenchmarkBase64Encode)
-    ->ArgsProduct({
-        // generate the num of strings
-        benchmark::CreateRange(10, 1000, 10),
-        // generate the length of each string
-        benchmark::CreateRange(10, 1000, 10),
-        benchmark::CreateRange(10, 1000, 10),
-    });
-*/
diff --git a/include/sled/synchronization/mutex.h b/include/sled/synchronization/mutex.h
index f27e39e..dc2cccf 100644
--- a/include/sled/synchronization/mutex.h
+++ b/include/sled/synchronization/mutex.h
@@ -5,12 +5,14 @@
  **/
 
 #pragma once
+#include "marl/conditionvariable.h"
 #ifndef SLED_SYNCHRONIZATION_MUTEX_H
 #define SLED_SYNCHRONIZATION_MUTEX_H
 
 #include "sled/units/time_delta.h"
 #include <chrono>
 #include <condition_variable>
+#include <marl/mutex.h>
 #include <mutex>
 #include <type_traits>
 
@@ -31,24 +33,26 @@ struct HasLockAndUnlock {
 };
 }// namespace internal
 
-class Mutex final {
-public:
-    Mutex() = default;
-    Mutex(const Mutex &) = delete;
-    Mutex &operator=(const Mutex &) = delete;
+using Mutex = marl::mutex;
 
-    inline void Lock() { impl_.lock(); };
-
-    inline bool TryLock() { return impl_.try_lock(); }
-
-    inline void AssertHeld() {}
-
-    inline void Unlock() { impl_.unlock(); }
-
-private:
-    std::mutex impl_;
-    friend class ConditionVariable;
-};
+// class Mutex final {
+// public:
+//     Mutex() = default;
+//     Mutex(const Mutex &) = delete;
+//     Mutex &operator=(const Mutex &) = delete;
+//
+//     inline void Lock() { impl_.lock(); };
+//
+//     inline bool TryLock() { return impl_.try_lock(); }
+//
+//     inline void AssertHeld() {}
+//
+//     inline void Unlock() { impl_.unlock(); }
+//
+// private:
+//     std::mutex impl_;
+//     friend class ConditionVariable;
+// };
 
 class RecursiveMutex final {
 public:
@@ -85,8 +89,22 @@ private:
     friend class ConditionVariable;
 };
 
-using MutexLock = LockGuard<Mutex>;
-using MutexGuard = LockGuard<Mutex>;
+class MutexGuard final {
+public:
+    MutexGuard(Mutex *mutex) : lock_(*mutex) {}
+
+    MutexGuard(const MutexGuard &) = delete;
+    MutexGuard &operator=(const MutexGuard &) = delete;
+
+private:
+    friend class ConditionVariable;
+    marl::lock lock_;
+};
+
+using MutexLock = MutexGuard;
+// using MutexGuard = marl::lock;
+// using MutexLock = LockGuard<Mutex>;
+// using MutexGuard = LockGuard<Mutex>;
 using RecursiveMutexLock = LockGuard<RecursiveMutex>;
 
 // class MutexLock final {
@@ -121,44 +139,77 @@ using RecursiveMutexLock = LockGuard<RecursiveMutex>;
 class ConditionVariable final {
 public:
     static constexpr TimeDelta kForever = TimeDelta::PlusInfinity();
-    ConditionVariable() = default;
-    ConditionVariable(const ConditionVariable &) = delete;
-    ConditionVariable &operator=(const ConditionVariable &) = delete;
 
-    template<typename Predicate>
-    inline bool Wait(LockGuard<Mutex> &guard, Predicate pred)
-    {
-        std::unique_lock<std::mutex> lock(guard.mutex_->impl_, std::adopt_lock);
-        cv_.wait(lock, pred);
-        return true;
-    }
-
-    template<typename Predicate>
-    inline bool
-    WaitFor(LockGuard<Mutex> &guard, TimeDelta timeout, Predicate pred)
-    {
-        std::unique_lock<std::mutex> lock(guard.mutex_->impl_, std::adopt_lock);
-        if (timeout == kForever) {
-            cv_.wait(lock, pred);
-            return true;
-        } else {
-            return cv_.wait_for(lock, std::chrono::milliseconds(timeout.ms()),
-                                pred);
-        }
-    }
-
-    // template<typename Predicate>
-    // bool WaitUntil(Mutex *mutex, TimeDelta timeout, Predicate pred)
-    // {}
+    // inline ConditionVariable();
 
     inline void NotifyOne() { cv_.notify_one(); }
 
     inline void NotifyAll() { cv_.notify_all(); }
 
+    template<typename Predicate>
+    inline void Wait(MutexLock &lock, Predicate &&pred)
+    {
+        cv_.wait(lock, std::forward<Predicate>(pred));
+    }
+
+    template<typename Predicate>
+    inline bool WaitFor(MutexLock &lock, TimeDelta timeout, Predicate &&pred)
+    {
+        if (timeout == TimeDelta::PlusInfinity()) {
+            cv_.wait(lock.lock_, std::forward<Predicate>(pred));
+            return true;
+        } else {
+            return cv_.wait_for(lock.lock_,
+                                std::chrono::milliseconds(timeout.ms()),
+                                std::forward<Predicate>(pred));
+        }
+    }
+
 private:
-    std::condition_variable cv_;
+    marl::ConditionVariable cv_;
 };
 
+// class ConditionVariable final {
+// public:
+//     static constexpr TimeDelta kForever = TimeDelta::PlusInfinity();
+//     ConditionVariable() = default;
+//     ConditionVariable(const ConditionVariable &) = delete;
+//     ConditionVariable &operator=(const ConditionVariable &) = delete;
+//
+//     template<typename Predicate>
+//     inline bool Wait(LockGuard<Mutex> &guard, Predicate pred)
+//     {
+//         std::unique_lock<std::mutex> lock(guard.mutex_->impl_, std::adopt_lock);
+//         cv_.wait(lock, pred);
+//         return true;
+//     }
+//
+//     template<typename Predicate>
+//     inline bool
+//     WaitFor(LockGuard<Mutex> &guard, TimeDelta timeout, Predicate pred)
+//     {
+//         std::unique_lock<std::mutex> lock(guard.mutex_->impl_, std::adopt_lock);
+//         if (timeout == kForever) {
+//             cv_.wait(lock, pred);
+//             return true;
+//         } else {
+//             return cv_.wait_for(lock, std::chrono::milliseconds(timeout.ms()),
+//                                 pred);
+//         }
+//     }
+//
+//     // template<typename Predicate>
+//     // bool WaitUntil(Mutex *mutex, TimeDelta timeout, Predicate pred)
+//     // {}
+//
+//     inline void NotifyOne() { cv_.notify_one(); }
+//
+//     inline void NotifyAll() { cv_.notify_all(); }
+//
+// private:
+//     std::condition_variable cv_;
+// };
+
 }// namespace sled
 
 #endif// SLED_SYNCHRONIZATION_MUTEX_H
diff --git a/include/sled/system/fiber/fiber_wait_group.h b/include/sled/system/fiber/fiber_wait_group.h
deleted file mode 100644
index b747a31..0000000
--- a/include/sled/system/fiber/fiber_wait_group.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#pragma once
-#ifndef SLED_SYSTEM_FIBER_FIBER_WAIT_GROUP_H
-#define SLED_SYSTEM_FIBER_FIBER_WAIT_GROUP_H
-#include <marl/waitgroup.h>
-
-namespace sled {
-using FiberWaitGroup = marl::WaitGroup;
-}
-
-#endif// SLED_SYSTEM_FIBER_FIBER_WAIT_GROUP_H
diff --git a/include/sled/system/fiber/fiber_scheduler.h b/include/sled/system/fiber/scheduler.h
similarity index 87%
rename from include/sled/system/fiber/fiber_scheduler.h
rename to include/sled/system/fiber/scheduler.h
index 24f611d..9b807a5 100644
--- a/include/sled/system/fiber/fiber_scheduler.h
+++ b/include/sled/system/fiber/scheduler.h
@@ -1,12 +1,12 @@
 #pragma once
-#ifndef SLED_SYSTEM_FIBER_FIBER_SCHEDULER_H
-#define SLED_SYSTEM_FIBER_FIBER_SCHEDULER_H
+#ifndef SLED_SYSTEM_FIBER_SCHEDULER_H
+#define SLED_SYSTEM_FIBER_SCHEDULER_H
 #include <marl/defer.h>
 #include <marl/scheduler.h>
 #include <marl/task.h>
 
 namespace sled {
-using FiberScheduler = marl::Scheduler;
+using Scheduler = marl::Scheduler;
 
 // schedule() schedules the task T to be asynchronously called using the
 // currently bound scheduler.
@@ -42,4 +42,4 @@ Schedule(Function &&f)
 }
 }// namespace sled
 
-#endif//  SLED_SYSTEM_FIBER_FIBER_SCHEDULER_H
+#endif//  SLED_SYSTEM_FIBER_SCHEDULER_H
diff --git a/include/sled/system/fiber/wait_group.h b/include/sled/system/fiber/wait_group.h
new file mode 100644
index 0000000..9dc5ad2
--- /dev/null
+++ b/include/sled/system/fiber/wait_group.h
@@ -0,0 +1,26 @@
+#pragma once
+#ifndef SLED_SYSTEM_FIBER_WAIT_GROUP_H
+#define SLED_SYSTEM_FIBER_WAIT_GROUP_H
+#include <marl/waitgroup.h>
+
+namespace sled {
+
+class WaitGroup final {
+public:
+    inline WaitGroup(unsigned int count = 0,
+                     marl::Allocator *allocator = marl::Allocator::Default)
+        : wg_(new marl::WaitGroup(count, allocator))
+    {}
+
+    inline void Add(unsigned int count = 1) const { wg_->add(count); };
+
+    inline bool Done() const { return wg_->done(); }
+
+    inline void Wait() const { wg_->wait(); }
+
+private:
+    mutable std::shared_ptr<marl::WaitGroup> wg_;
+};
+}// namespace sled
+
+#endif// SLED_SYSTEM_FIBER_WAIT_GROUP_H
diff --git a/src/cleanup_test.cc b/src/cleanup_test.cc
new file mode 100644
index 0000000..76ba443
--- /dev/null
+++ b/src/cleanup_test.cc
@@ -0,0 +1,16 @@
+#include <gtest/gtest.h>
+#include <sled/cleanup.h>
+#include <sled/random.h>
+
+TEST(Cleanup, TestCleanup)
+{
+    sled::Random rand(1314);
+    for (int i = 0; i < 100; ++i) {
+        int a = rand.Rand(10000);
+        int b = rand.Rand(10000, 20000);
+        {
+            sled::Cleanup<> c([=, &a]() { a = b; });
+        }
+        ASSERT_EQ(a, b);
+    }
+}
diff --git a/src/filesystem/path_test.cc b/src/filesystem/path_test.cc
new file mode 100644
index 0000000..e54bc7f
--- /dev/null
+++ b/src/filesystem/path_test.cc
@@ -0,0 +1,23 @@
+#include <gtest/gtest.h>
+#include <sled/filesystem/path.h>
+
+TEST(Path, TestCurrent)
+{
+    sled::Path path = sled::Path::Current();
+    std::string str = path.ToString();
+    EXPECT_FALSE(str.empty());
+}
+
+TEST(Path, TestHome)
+{
+    sled::Path path = sled::Path::Home();
+    std::string str = path.ToString();
+    EXPECT_FALSE(str.empty());
+}
+
+TEST(Path, TestTempDir)
+{
+    sled::Path path = sled::Path::TempDir();
+    std::string str = path.ToString();
+    EXPECT_FALSE(str.empty());
+}
diff --git a/src/network/async_resolver.cc b/src/network/async_resolver.cc
index eb2b7d9..4ab7b75 100644
--- a/src/network/async_resolver.cc
+++ b/src/network/async_resolver.cc
@@ -45,7 +45,6 @@ AsyncResolver::AsyncResolver() : error_(-1), state_(new State) {}
 AsyncResolver::~AsyncResolver()
 {
     MutexLock lock(&state_->mutex);
-    ;
     state_->status = State::Status::kDead;
 }
 
diff --git a/src/network/physical_socket_server.cc b/src/network/physical_socket_server.cc
index d107b73..d52b1d1 100644
--- a/src/network/physical_socket_server.cc
+++ b/src/network/physical_socket_server.cc
@@ -400,7 +400,7 @@ void
 PhysicalSocket::SetError(int error)
 {
     // MutexLock lock(&mutex_);
-    LockGuard<Mutex> lock(&mutex_);
+    MutexGuard lock(&mutex_);
     error_ = error;
 }
 
diff --git a/src/status_or_test.cc b/src/status_or_test.cc
new file mode 100644
index 0000000..e117c1e
--- /dev/null
+++ b/src/status_or_test.cc
@@ -0,0 +1,22 @@
+#include <gtest/gtest.h>
+#include <sled/status_or.h>
+
+TEST(StatusOr, TestStatusOr)
+{
+    sled::StatusOr<int> so;
+    EXPECT_FALSE(so.ok());
+    so = sled::StatusOr<int>(1);
+    EXPECT_TRUE(so.ok());
+    EXPECT_EQ(so.value(), 1);
+    EXPECT_EQ(so.status().code(), sled::StatusCode::kOk);
+}
+
+TEST(StatusOr, make_status_or)
+{
+    auto from_raw_str = sled::make_status_or("hello");
+    auto from_string = sled::make_status_or(std::string("world"));
+    EXPECT_TRUE(from_raw_str.ok());
+    EXPECT_TRUE(from_string.ok());
+    EXPECT_EQ(from_raw_str.value(), "hello");
+    EXPECT_EQ(from_string.value(), "world");
+}
diff --git a/src/strings/base64.cc b/src/strings/base64.cc
index ded6149..5b81f20 100644
--- a/src/strings/base64.cc
+++ b/src/strings/base64.cc
@@ -45,6 +45,11 @@ Base64::Encode(const std::string &input)
         }
     }
 
+    /**
+     * value_bits      
+     * 2           ->  4  -> (8 - value_bits - 2)
+     * 4           ->  2  -> (8 - value_bits - 2)
+     **/
     if (value_bits > 0) {
         ss << kBase64Chars[((value << 8) >> (value_bits + 2)) & 0x3F];
     }
@@ -63,10 +68,10 @@ Base64::Decode(const std::string &input)
     for (unsigned char c : input) {
         if (-1 != kInvBase64Chars[c]) {
             // valid base64 character
-            value = (value << 6) + kInvBase64Chars[c];
+            value = (value << 6) | kInvBase64Chars[c];
             value_bits += 6;
-            if (value_bits >= 0) {
-                ss << char((value >> value_bits) & 0xFF);
+            if (value_bits >= 8) {
+                ss << char((value >> (value_bits - 8)) & 0xFF);
                 value_bits -= 8;
             }
         } else if (c == '=') {
@@ -81,6 +86,7 @@ Base64::Decode(const std::string &input)
         }
         ++index;
     }
+
     return make_status_or<std::string>(ss.str());
 }
 }// namespace sled
diff --git a/src/strings/base64_test.cc b/src/strings/base64_test.cc
new file mode 100644
index 0000000..d8c2963
--- /dev/null
+++ b/src/strings/base64_test.cc
@@ -0,0 +1,23 @@
+#include <gtest/gtest.h>
+#include <sled/strings/base64.h>
+
+#define CONCAT_IMPL(A, B) A##B
+#define CONCAT(A, B) CONCAT_IMPL(A, B)
+
+#define TEST_ENCODE_DECODE(base64, text)                                       \
+    do {                                                                       \
+        ASSERT_EQ(sled::Base64::Encode(text), base64);                         \
+        auto CONCAT(res, __LINE__) = sled::Base64::Decode(base64);             \
+        ASSERT_TRUE(CONCAT(res, __LINE__).ok());                               \
+        ASSERT_EQ(CONCAT(res, __LINE__).value(), text);                        \
+    } while (0)
+
+TEST(Base64, EncodeAndDecode)
+{
+    TEST_ENCODE_DECODE("aGVsbG8gd29ybGQK", "hello world\n");
+    TEST_ENCODE_DECODE("U2VuZCByZWluZm9yY2VtZW50cwo=", "Send reinforcements\n");
+    TEST_ENCODE_DECODE("", "");
+    TEST_ENCODE_DECODE("AA==", std::string("\0", 1));
+    TEST_ENCODE_DECODE("AAA=", std::string("\0\0", 2));
+    TEST_ENCODE_DECODE("AAAA", std::string("\0\0\0", 3));
+}
diff --git a/src/system/fiber/fiber_bench.cc b/src/system/fiber/fiber_bench.cc
new file mode 100644
index 0000000..cc36772
--- /dev/null
+++ b/src/system/fiber/fiber_bench.cc
@@ -0,0 +1,25 @@
+#include <benchmark/benchmark.h>
+#include <sled/system/fiber/scheduler.h>
+#include <sled/system/fiber/wait_group.h>
+
+static void
+MultiQueue(benchmark::State &state)
+{
+    sled::Scheduler scheduler(sled::Scheduler::Config::allCores());
+    scheduler.bind();
+    defer(scheduler.unbind());
+    const int num_tasks = state.range(0);
+    sled::WaitGroup wg(num_tasks);
+    sled::WaitGroup start_flag(1);
+
+    for (int i = 0; i < num_tasks; i++) {
+        sled::Schedule([=] {
+            start_flag.Wait();
+            wg.Done();
+        });
+    }
+    start_flag.Done();
+    wg.Wait();
+}
+
+BENCHMARK(MultiQueue)->RangeMultiplier(10)->Range(10, 10000);
diff --git a/src/system/fiber/fiber_test.cc b/src/system/fiber/fiber_test.cc
new file mode 100644
index 0000000..75f8f36
--- /dev/null
+++ b/src/system/fiber/fiber_test.cc
@@ -0,0 +1,25 @@
+#include <gtest/gtest.h>
+#include <sled/system/fiber/scheduler.h>
+#include <sled/system/fiber/wait_group.h>
+
+TEST(FiberScheduler, TestFiberScheduler)
+{
+    sled::Scheduler scheduler(sled::Scheduler::Config::allCores());
+    scheduler.bind();
+    defer(scheduler.unbind());
+
+    std::atomic<int> counter = {0};
+    sled::WaitGroup wg(1);
+    sled::WaitGroup wg2(1000);
+    for (int i = 0; i < 1000; i++) {
+        sled::Schedule([&] {
+            wg.Wait();
+            wg2.Done();
+            counter++;
+        });
+    }
+
+    sled::Schedule([=] { wg.Done(); });
+    wg2.Wait();
+    ASSERT_EQ(counter.load(), 1000);
+}