diff --git a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp
index bb90e6d..0d230ad 100644
--- a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.cpp
@@ -64,7 +64,7 @@
     return std::make_unique<TestBlockServer>(queue_, misc_name_);
 }
 
-std::shared_ptr<IBlockServerOpener> TestBlockServerFactory::CreateOpener(
+std::shared_ptr<TestBlockServerOpener> TestBlockServerFactory::CreateTestOpener(
         const std::string& misc_name) {
     if (queues_.count(misc_name)) {
         LOG(ERROR) << "Cannot create opener for " << misc_name << ", already exists";
@@ -75,6 +75,11 @@
     return std::make_shared<TestBlockServerOpener>(queue, misc_name);
 }
 
+std::shared_ptr<IBlockServerOpener> TestBlockServerFactory::CreateOpener(
+        const std::string& misc_name) {
+    return CreateTestOpener(misc_name);
+}
+
 bool TestBlockServerFactory::DeleteQueue(const std::string& misc_name) {
     auto iter = queues_.find(misc_name);
     if (iter == queues_.end()) {
diff --git a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h
index e5c6985..ec0bd29 100644
--- a/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h
+++ b/fs_mgr/libsnapshot/snapuserd/testing/host_harness.h
@@ -68,6 +68,7 @@
 class TestBlockServerFactory final : public IBlockServerFactory {
   public:
     std::shared_ptr<IBlockServerOpener> CreateOpener(const std::string& misc_name) override;
+    std::shared_ptr<TestBlockServerOpener> CreateTestOpener(const std::string& misc_name);
     bool DeleteQueue(const std::string& misc_name);
 
   private:
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
index a6a3eb8..6dbae81 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/read_worker.h
@@ -33,9 +33,11 @@
     bool Run();
     bool Init() override;
     void CloseFds() override;
+    bool RequestSectors(uint64_t sector, uint64_t size) override;
+
+    IBlockServer* block_server() const { return block_server_.get(); }
 
   private:
-    bool RequestSectors(uint64_t sector, uint64_t size) override;
     bool SendBufferedIo();
 
     bool ProcessCowOp(const CowOperation* cow_op, void* buffer);
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
index 9c92384..c5ccb0d 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
@@ -39,6 +39,8 @@
 #include <snapuserd/dm_user_block_server.h>
 #include <storage_literals/storage_literals.h>
 #include "handler_manager.h"
+#include "merge_worker.h"
+#include "read_worker.h"
 #include "snapuserd_core.h"
 #include "testing/dm_user_harness.h"
 #include "testing/host_harness.h"
@@ -56,6 +58,9 @@
 using namespace std::chrono_literals;
 using namespace android::dm;
 using namespace std;
+using testing::AssertionFailure;
+using testing::AssertionResult;
+using testing::AssertionSuccess;
 
 class SnapuserdTestBase : public ::testing::Test {
   protected:
@@ -776,6 +781,110 @@
     ValidateMerge();
 }
 
+class HandlerTest : public SnapuserdTestBase {
+  protected:
+    void SetUp() override;
+    void TearDown() override;
+
+    AssertionResult ReadSectors(sector_t sector, uint64_t size, void* buffer);
+
+    TestBlockServerFactory factory_;
+    std::shared_ptr<TestBlockServerOpener> opener_;
+    std::shared_ptr<SnapshotHandler> handler_;
+    std::unique_ptr<ReadWorker> read_worker_;
+    TestBlockServer* block_server_;
+    std::future<bool> handler_thread_;
+};
+
+void HandlerTest::SetUp() {
+    ASSERT_NO_FATAL_FAILURE(SnapuserdTestBase::SetUp());
+    ASSERT_NO_FATAL_FAILURE(CreateBaseDevice());
+    ASSERT_NO_FATAL_FAILURE(CreateCowDevice());
+    ASSERT_NO_FATAL_FAILURE(SetDeviceControlName());
+
+    opener_ = factory_.CreateTestOpener(system_device_ctrl_name_);
+    ASSERT_NE(opener_, nullptr);
+
+    handler_ = std::make_shared<SnapshotHandler>(system_device_ctrl_name_, cow_system_->path,
+                                                 base_dev_->GetPath(), base_dev_->GetPath(),
+                                                 opener_, 1, false, false);
+    ASSERT_TRUE(handler_->InitCowDevice());
+    ASSERT_TRUE(handler_->InitializeWorkers());
+
+    read_worker_ = std::make_unique<ReadWorker>(cow_system_->path, base_dev_->GetPath(),
+                                                system_device_ctrl_name_, base_dev_->GetPath(),
+                                                handler_->GetSharedPtr(), opener_);
+    ASSERT_TRUE(read_worker_->Init());
+    block_server_ = static_cast<TestBlockServer*>(read_worker_->block_server());
+
+    handler_thread_ = std::async(std::launch::async, &SnapshotHandler::Start, handler_.get());
+}
+
+void HandlerTest::TearDown() {
+    ASSERT_TRUE(factory_.DeleteQueue(system_device_ctrl_name_));
+    ASSERT_TRUE(handler_thread_.get());
+    SnapuserdTestBase::TearDown();
+}
+
+AssertionResult HandlerTest::ReadSectors(sector_t sector, uint64_t size, void* buffer) {
+    if (!read_worker_->RequestSectors(sector, size)) {
+        return AssertionFailure() << "request sectors failed";
+    }
+
+    std::string result = std::move(block_server_->sent_io());
+    if (result.size() != size) {
+        return AssertionFailure() << "size mismatch in result, got " << result.size()
+                                  << ", expected " << size;
+    }
+
+    memcpy(buffer, result.data(), size);
+    return AssertionSuccess();
+}
+
+// This test mirrors ReadSnapshotDeviceAndValidate.
+TEST_F(HandlerTest, Read) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(size_);
+
+    // COPY
+    loff_t offset = 0;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get(), size_), 0);
+
+    // REPLACE
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + size_, size_), 0);
+
+    // ZERO
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 2), size_), 0);
+
+    // REPLACE
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 3), size_), 0);
+
+    // XOR
+    offset += size_;
+    ASSERT_TRUE(ReadSectors(offset / SECTOR_SIZE, size_, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 4), size_), 0);
+}
+
+TEST_F(HandlerTest, ReadUnalignedSector) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(BLOCK_SZ);
+
+    ASSERT_TRUE(ReadSectors(1, BLOCK_SZ, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get() + SECTOR_SIZE, BLOCK_SZ), 0);
+}
+
+TEST_F(HandlerTest, ReadUnalignedSize) {
+    std::unique_ptr<uint8_t[]> snapuserd_buffer = std::make_unique<uint8_t[]>(SECTOR_SIZE);
+
+    ASSERT_TRUE(ReadSectors(0, SECTOR_SIZE, snapuserd_buffer.get()));
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), orig_buffer_.get(), SECTOR_SIZE), 0);
+}
+
 }  // namespace snapshot
 }  // namespace android