diff --git a/Android.bp b/Android.bp
index 11c03b4..d74e78f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -792,6 +792,7 @@
         "libcurl_http_fetcher_unittest.cc",
         "payload_consumer/bzip_extent_writer_unittest.cc",
         "payload_consumer/cached_file_descriptor_unittest.cc",
+        "payload_consumer/cow_writer_file_descriptor_unittest.cc",
         "payload_consumer/certificate_parser_android_unittest.cc",
         "payload_consumer/delta_performer_integration_test.cc",
         "payload_consumer/delta_performer_unittest.cc",
diff --git a/payload_consumer/cow_writer_file_descriptor_unittest.cc b/payload_consumer/cow_writer_file_descriptor_unittest.cc
new file mode 100644
index 0000000..c596e3b
--- /dev/null
+++ b/payload_consumer/cow_writer_file_descriptor_unittest.cc
@@ -0,0 +1,120 @@
+//
+// Copyright (C) 2021 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.
+//
+
+#include "update_engine/payload_consumer/cow_writer_file_descriptor.h"
+
+#include <cstring>
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include <android-base/unique_fd.h>
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+#include <libsnapshot/snapshot_writer.h>
+
+#include "update_engine/common/utils.h"
+
+namespace chromeos_update_engine {
+constexpr size_t BLOCK_SIZE = 4096;
+constexpr size_t PARTITION_SIZE = BLOCK_SIZE * 10;
+
+using android::base::unique_fd;
+using android::snapshot::CompressedSnapshotWriter;
+using android::snapshot::CowOptions;
+using android::snapshot::ISnapshotWriter;
+
+class CowWriterFileDescriptorUnittest : public ::testing::Test {
+ public:
+  void SetUp() override {
+    ASSERT_EQ(ftruncate64(cow_device_file_.fd(), PARTITION_SIZE), 0)
+        << "Failed to truncate cow_device file to " << PARTITION_SIZE
+        << strerror(errno);
+    ASSERT_EQ(ftruncate64(cow_source_file_.fd(), PARTITION_SIZE), 0)
+        << "Failed to truncate cow_source file to " << PARTITION_SIZE
+        << strerror(errno);
+  }
+
+  std::unique_ptr<CompressedSnapshotWriter> GetCowWriter() {
+    const CowOptions options{.block_size = BLOCK_SIZE, .compression = "gz"};
+    auto snapshot_writer = std::make_unique<CompressedSnapshotWriter>(options);
+    int fd = open(cow_device_file_.path().c_str(), O_RDWR);
+    EXPECT_NE(fd, -1);
+    EXPECT_TRUE(snapshot_writer->SetCowDevice(unique_fd{fd}));
+    snapshot_writer->SetSourceDevice(cow_source_file_.path());
+    return snapshot_writer;
+  }
+  CowWriterFileDescriptor GetCowFd() {
+    auto cow_writer = GetCowWriter();
+    return CowWriterFileDescriptor{std::move(cow_writer)};
+  }
+
+  ScopedTempFile cow_source_file_{"cow_source.XXXXXX", true};
+  ScopedTempFile cow_device_file_{"cow_device.XXXXXX", true};
+};
+
+TEST_F(CowWriterFileDescriptorUnittest, ReadAfterWrite) {
+  std::vector<unsigned char> buffer;
+  buffer.resize(BLOCK_SIZE);
+  std::fill(buffer.begin(), buffer.end(), 234);
+
+  std::vector<unsigned char> verity_data;
+  verity_data.resize(BLOCK_SIZE);
+  std::fill(verity_data.begin(), verity_data.end(), 0xAA);
+
+  auto cow_writer = GetCowWriter();
+  cow_writer->Initialize();
+
+  // Simulate Writing InstallOp data
+  ASSERT_TRUE(cow_writer->AddRawBlocks(0, buffer.data(), buffer.size()));
+  ASSERT_TRUE(cow_writer->AddZeroBlocks(1, 2));
+  ASSERT_TRUE(cow_writer->AddCopy(3, 1));
+  // Fake label to simulate "end of install"
+  ASSERT_TRUE(cow_writer->AddLabel(23));
+  ASSERT_TRUE(
+      cow_writer->AddRawBlocks(4, verity_data.data(), verity_data.size()));
+  ASSERT_TRUE(cow_writer->Finalize());
+
+  cow_writer = GetCowWriter();
+  ASSERT_NE(nullptr, cow_writer);
+  ASSERT_TRUE(cow_writer->InitializeAppend(23));
+  auto cow_fd =
+      std::make_unique<CowWriterFileDescriptor>(std::move(cow_writer));
+
+  ASSERT_EQ((ssize_t)BLOCK_SIZE * 4, cow_fd->Seek(BLOCK_SIZE * 4, SEEK_SET));
+  std::vector<unsigned char> read_back(4096);
+  ASSERT_EQ((ssize_t)read_back.size(),
+            cow_fd->Read(read_back.data(), read_back.size()));
+  ASSERT_EQ(verity_data, read_back);
+
+  // Since we didn't write anything to this instance of cow_fd, destructor
+  // should not call Finalize(). As finalize will drop ops after resume label,
+  // causing subsequent reads to fail.
+  cow_writer = GetCowWriter();
+  ASSERT_NE(nullptr, cow_writer);
+  ASSERT_TRUE(cow_writer->InitializeAppend(23));
+  cow_fd = std::make_unique<CowWriterFileDescriptor>(std::move(cow_writer));
+
+  ASSERT_EQ((ssize_t)BLOCK_SIZE * 4, cow_fd->Seek(BLOCK_SIZE * 4, SEEK_SET));
+  ASSERT_EQ((ssize_t)read_back.size(),
+            cow_fd->Read(read_back.data(), read_back.size()));
+  ASSERT_EQ(verity_data, read_back)
+      << "Could not read verity data afeter InitializeAppend() => Read() => "
+         "InitializeAppend() sequence. If no writes happened while CowWriterFd "
+         "is open, Finalize() should not be called.";
+}
+
+}  // namespace chromeos_update_engine
diff --git a/payload_consumer/filesystem_verifier_action_unittest.cc b/payload_consumer/filesystem_verifier_action_unittest.cc
index d2a015d..586662d 100644
--- a/payload_consumer/filesystem_verifier_action_unittest.cc
+++ b/payload_consumer/filesystem_verifier_action_unittest.cc
@@ -488,7 +488,6 @@
 }
 
 TEST_F(FilesystemVerifierActionTest, ReadAfterWrite) {
-  constexpr auto BLOCK_SIZE = 4096;
   ScopedTempFile cow_device_file("cow_device.XXXXXX", true);
   android::snapshot::CompressedSnapshotWriter snapshot_writer{
       {.block_size = BLOCK_SIZE}};
@@ -507,6 +506,12 @@
   ASSERT_TRUE(snapshot_writer.Finalize());
   cow_reader = snapshot_writer.OpenReader();
   ASSERT_NE(cow_reader, nullptr);
+  std::vector<unsigned char> read_back;
+  read_back.resize(buffer.size());
+  cow_reader->Seek(BLOCK_SIZE, SEEK_SET);
+  const auto bytes_read = cow_reader->Read(read_back.data(), read_back.size());
+  ASSERT_EQ((size_t)(bytes_read), BLOCK_SIZE);
+  ASSERT_EQ(read_back, buffer);
 }
 
 }  // namespace chromeos_update_engine