Copy a version of download action for ChromeOS

DownloadAction contains many cros specific stuff, such as p2p, system
state. Many of these cros bits are used in a fragile way in aosp. It's
better if we maintain two independent download actions.

Test: treehugger
Bug: 175042161
Change-Id: Iaaed269b3886a068bfcb4bcac12aca99b9cf6970
diff --git a/cros/download_action_chromeos_unittest.cc b/cros/download_action_chromeos_unittest.cc
new file mode 100644
index 0000000..93c39ff
--- /dev/null
+++ b/cros/download_action_chromeos_unittest.cc
@@ -0,0 +1,697 @@
+//
+// Copyright (C) 2011 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 <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include <base/bind.h>
+#include <base/files/file_path.h>
+#include <base/files/file_util.h>
+#include <base/location.h>
+#include <base/strings/stringprintf.h>
+#include <brillo/message_loops/fake_message_loop.h>
+#include <brillo/message_loops/message_loop.h>
+
+#include "update_engine/common/action_pipe.h"
+#include "update_engine/common/hash_calculator.h"
+#include "update_engine/common/mock_download_action.h"
+#include "update_engine/common/mock_http_fetcher.h"
+#include "update_engine/common/test_utils.h"
+#include "update_engine/common/utils.h"
+#include "update_engine/cros/download_action_chromeos.h"
+#include "update_engine/cros/fake_p2p_manager_configuration.h"
+#include "update_engine/cros/fake_system_state.h"
+#include "update_engine/payload_consumer/mock_file_writer.h"
+#include "update_engine/update_manager/fake_update_manager.h"
+
+namespace chromeos_update_engine {
+
+using base::FilePath;
+using base::ReadFileToString;
+using base::WriteFile;
+using std::string;
+using std::unique_ptr;
+using testing::_;
+using testing::AtLeast;
+using testing::InSequence;
+using testing::Return;
+using testing::SetArgPointee;
+
+class DownloadActionChromeosTest : public ::testing::Test {
+  void SetUp() { FakeSystemState::CreateInstance(); }
+};
+
+namespace {
+
+class DownloadActionTestProcessorDelegate : public ActionProcessorDelegate {
+ public:
+  DownloadActionTestProcessorDelegate()
+      : processing_done_called_(false), expected_code_(ErrorCode::kSuccess) {}
+  ~DownloadActionTestProcessorDelegate() override {
+    EXPECT_TRUE(processing_done_called_);
+  }
+  void ProcessingDone(const ActionProcessor* processor,
+                      ErrorCode code) override {
+    brillo::MessageLoop::current()->BreakLoop();
+    brillo::Blob found_data;
+    ASSERT_TRUE(utils::ReadFile(path_, &found_data));
+    if (expected_code_ != ErrorCode::kDownloadWriteError) {
+      ASSERT_EQ(expected_data_.size(), found_data.size());
+      for (unsigned i = 0; i < expected_data_.size(); i++) {
+        EXPECT_EQ(expected_data_[i], found_data[i]);
+      }
+    }
+    processing_done_called_ = true;
+  }
+
+  void ActionCompleted(ActionProcessor* processor,
+                       AbstractAction* action,
+                       ErrorCode code) override {
+    const string type = action->Type();
+    if (type == DownloadActionChromeos::StaticType()) {
+      EXPECT_EQ(expected_code_, code);
+      p2p_file_id_ =
+          static_cast<DownloadActionChromeos*>(action)->p2p_file_id();
+    } else {
+      EXPECT_EQ(ErrorCode::kSuccess, code);
+    }
+  }
+
+  string path_;
+  brillo::Blob expected_data_;
+  bool processing_done_called_;
+  ErrorCode expected_code_;
+  string p2p_file_id_;
+};
+
+class TestDirectFileWriter : public DirectFileWriter {
+ public:
+  TestDirectFileWriter() : fail_write_(0), current_write_(0) {}
+  void set_fail_write(int fail_write) { fail_write_ = fail_write; }
+
+  virtual bool Write(const void* bytes, size_t count) {
+    if (++current_write_ == fail_write_) {
+      return false;
+    }
+    return DirectFileWriter::Write(bytes, count);
+  }
+
+ private:
+  // If positive, fail on the |fail_write_| call to Write.
+  int fail_write_;
+  int current_write_;
+};
+
+void StartProcessorInRunLoop(ActionProcessor* processor,
+                             MockHttpFetcher* http_fetcher) {
+  processor->StartProcessing();
+  http_fetcher->SetOffset(1);
+}
+
+void TestWithData(const brillo::Blob& data,
+                  int fail_write,
+                  bool use_download_delegate) {
+  FakeSystemState::CreateInstance();
+  brillo::FakeMessageLoop loop(nullptr);
+  loop.SetAsCurrent();
+
+  ScopedTempFile output_temp_file;
+  TestDirectFileWriter writer;
+  EXPECT_EQ(
+      0, writer.Open(output_temp_file.path().c_str(), O_WRONLY | O_CREAT, 0));
+  writer.set_fail_write(fail_write);
+
+  uint64_t size = data.size() - 1;
+  InstallPlan install_plan;
+  install_plan.payloads.push_back(
+      {.size = size, .type = InstallPayloadType::kDelta});
+  // We pull off the first byte from data and seek past it.
+  EXPECT_TRUE(HashCalculator::RawHashOfBytes(
+      &data[1], data.size() - 1, &install_plan.payloads[0].hash));
+  install_plan.source_slot = 0;
+  install_plan.target_slot = 1;
+  // We mark both slots as bootable. Only the target slot should be unbootable
+  // after the download starts.
+  FakeSystemState::Get()->fake_boot_control()->SetSlotBootable(
+      install_plan.source_slot, true);
+  FakeSystemState::Get()->fake_boot_control()->SetSlotBootable(
+      install_plan.target_slot, true);
+  auto feeder_action = std::make_unique<ObjectFeederAction<InstallPlan>>();
+  feeder_action->set_obj(install_plan);
+  MockPrefs prefs;
+  MockHttpFetcher* http_fetcher =
+      new MockHttpFetcher(data.data(), data.size(), nullptr);
+  // takes ownership of passed in HttpFetcher
+  auto download_action = std::make_unique<DownloadActionChromeos>(
+      &prefs,
+      FakeSystemState::Get()->boot_control(),
+      FakeSystemState::Get()->hardware(),
+      http_fetcher,
+      false /* interactive */);
+  download_action->SetTestFileWriter(&writer);
+  BondActions(feeder_action.get(), download_action.get());
+  MockDownloadActionDelegate download_delegate;
+  if (use_download_delegate) {
+    InSequence s;
+    download_action->set_delegate(&download_delegate);
+    if (data.size() > kMockHttpFetcherChunkSize)
+      EXPECT_CALL(download_delegate,
+                  BytesReceived(_, kMockHttpFetcherChunkSize, _));
+    EXPECT_CALL(download_delegate, BytesReceived(_, _, _)).Times(AtLeast(1));
+    EXPECT_CALL(download_delegate, DownloadComplete())
+        .Times(fail_write == 0 ? 1 : 0);
+  }
+  DownloadActionTestProcessorDelegate delegate;
+  delegate.expected_code_ =
+      (fail_write > 0) ? ErrorCode::kDownloadWriteError : ErrorCode::kSuccess;
+  delegate.expected_data_ = brillo::Blob(data.begin() + 1, data.end());
+  delegate.path_ = output_temp_file.path();
+  ActionProcessor processor;
+  processor.set_delegate(&delegate);
+  processor.EnqueueAction(std::move(feeder_action));
+  processor.EnqueueAction(std::move(download_action));
+
+  loop.PostTask(FROM_HERE,
+                base::Bind(&StartProcessorInRunLoop, &processor, http_fetcher));
+  loop.Run();
+  EXPECT_FALSE(loop.PendingTasks());
+
+  EXPECT_TRUE(FakeSystemState::Get()->fake_boot_control()->IsSlotBootable(
+      install_plan.source_slot));
+  EXPECT_FALSE(FakeSystemState::Get()->fake_boot_control()->IsSlotBootable(
+      install_plan.target_slot));
+}
+}  // namespace
+
+TEST(DownloadActionTest, SimpleTest) {
+  brillo::Blob small;
+  const char* foo = "foo";
+  small.insert(small.end(), foo, foo + strlen(foo));
+  TestWithData(small,
+               0,      // fail_write
+               true);  // use_download_delegate
+}
+
+TEST(DownloadActionTest, LargeTest) {
+  brillo::Blob big(5 * kMockHttpFetcherChunkSize);
+  char c = '0';
+  for (unsigned int i = 0; i < big.size(); i++) {
+    big[i] = c;
+    c = ('9' == c) ? '0' : c + 1;
+  }
+  TestWithData(big,
+               0,      // fail_write
+               true);  // use_download_delegate
+}
+
+TEST(DownloadActionTest, FailWriteTest) {
+  brillo::Blob big(5 * kMockHttpFetcherChunkSize);
+  char c = '0';
+  for (unsigned int i = 0; i < big.size(); i++) {
+    big[i] = c;
+    c = ('9' == c) ? '0' : c + 1;
+  }
+  TestWithData(big,
+               2,      // fail_write
+               true);  // use_download_delegate
+}
+
+TEST(DownloadActionTest, NoDownloadDelegateTest) {
+  brillo::Blob small;
+  const char* foo = "foofoo";
+  small.insert(small.end(), foo, foo + strlen(foo));
+  TestWithData(small,
+               0,       // fail_write
+               false);  // use_download_delegate
+}
+
+TEST(DownloadActionTest, MultiPayloadProgressTest) {
+  std::vector<brillo::Blob> payload_datas;
+  // the first payload must be the largest, as it's the actual payload used by
+  // the MockHttpFetcher for all downloaded data.
+  payload_datas.emplace_back(4 * kMockHttpFetcherChunkSize + 256);
+  payload_datas.emplace_back(2 * kMockHttpFetcherChunkSize);
+  brillo::FakeMessageLoop loop(nullptr);
+  loop.SetAsCurrent();
+  EXPECT_CALL(*FakeSystemState::Get()->mock_payload_state(), NextPayload())
+      .WillOnce(Return(true));
+
+  MockFileWriter mock_file_writer;
+  EXPECT_CALL(mock_file_writer, Close()).WillRepeatedly(Return(0));
+  EXPECT_CALL(mock_file_writer, Write(_, _, _))
+      .WillRepeatedly(
+          DoAll(SetArgPointee<2>(ErrorCode::kSuccess), Return(true)));
+
+  InstallPlan install_plan;
+  uint64_t total_expected_download_size{0};
+  for (const auto& data : payload_datas) {
+    uint64_t size = data.size();
+    install_plan.payloads.push_back(
+        {.size = size, .type = InstallPayloadType::kFull});
+    total_expected_download_size += size;
+  }
+  auto feeder_action = std::make_unique<ObjectFeederAction<InstallPlan>>();
+  feeder_action->set_obj(install_plan);
+  MockPrefs prefs;
+  MockHttpFetcher* http_fetcher = new MockHttpFetcher(
+      payload_datas[0].data(), payload_datas[0].size(), nullptr);
+  // takes ownership of passed in HttpFetcher
+  auto download_action = std::make_unique<DownloadActionChromeos>(
+      &prefs,
+      FakeSystemState::Get()->boot_control(),
+      FakeSystemState::Get()->hardware(),
+      http_fetcher,
+      false /* interactive */);
+  download_action->SetTestFileWriter(&mock_file_writer);
+  BondActions(feeder_action.get(), download_action.get());
+  MockDownloadActionDelegate download_delegate;
+  {
+    InSequence s;
+    download_action->set_delegate(&download_delegate);
+    // these are hand-computed based on the payloads specified above
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              kMockHttpFetcherChunkSize,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              kMockHttpFetcherChunkSize * 2,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              kMockHttpFetcherChunkSize * 3,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              kMockHttpFetcherChunkSize * 4,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(256,
+                              kMockHttpFetcherChunkSize * 4 + 256,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              kMockHttpFetcherChunkSize * 5 + 256,
+                              total_expected_download_size));
+    EXPECT_CALL(download_delegate,
+                BytesReceived(kMockHttpFetcherChunkSize,
+                              total_expected_download_size,
+                              total_expected_download_size));
+  }
+  ActionProcessor processor;
+  processor.EnqueueAction(std::move(feeder_action));
+  processor.EnqueueAction(std::move(download_action));
+
+  loop.PostTask(
+      FROM_HERE,
+      base::Bind(
+          [](ActionProcessor* processor) { processor->StartProcessing(); },
+          base::Unretained(&processor)));
+  loop.Run();
+  EXPECT_FALSE(loop.PendingTasks());
+}
+
+namespace {
+class TerminateEarlyTestProcessorDelegate : public ActionProcessorDelegate {
+ public:
+  void ProcessingStopped(const ActionProcessor* processor) {
+    brillo::MessageLoop::current()->BreakLoop();
+  }
+};
+
+void TerminateEarlyTestStarter(ActionProcessor* processor) {
+  processor->StartProcessing();
+  CHECK(processor->IsRunning());
+  processor->StopProcessing();
+}
+
+void TestTerminateEarly(bool use_download_delegate) {
+  FakeSystemState::CreateInstance();
+  brillo::FakeMessageLoop loop(nullptr);
+  loop.SetAsCurrent();
+
+  brillo::Blob data(kMockHttpFetcherChunkSize + kMockHttpFetcherChunkSize / 2);
+  memset(data.data(), 0, data.size());
+
+  ScopedTempFile temp_file;
+  {
+    DirectFileWriter writer;
+    EXPECT_EQ(0, writer.Open(temp_file.path().c_str(), O_WRONLY | O_CREAT, 0));
+
+    // takes ownership of passed in HttpFetcher
+    auto feeder_action = std::make_unique<ObjectFeederAction<InstallPlan>>();
+    InstallPlan install_plan;
+    install_plan.payloads.resize(1);
+    feeder_action->set_obj(install_plan);
+
+    MockPrefs prefs;
+    auto download_action = std::make_unique<DownloadAction>(
+        &prefs,
+        FakeSystemState::Get()->boot_control(),
+        FakeSystemState::Get()->hardware(),
+        new MockHttpFetcher(data.data(), data.size(), nullptr),
+        false /* interactive */);
+    download_action->SetTestFileWriter(&writer);
+    MockDownloadActionDelegate download_delegate;
+    if (use_download_delegate) {
+      download_action->set_delegate(&download_delegate);
+      EXPECT_CALL(download_delegate, BytesReceived(_, _, _)).Times(0);
+    }
+    TerminateEarlyTestProcessorDelegate delegate;
+    ActionProcessor processor;
+    processor.set_delegate(&delegate);
+    BondActions(feeder_action.get(), download_action.get());
+    processor.EnqueueAction(std::move(feeder_action));
+    processor.EnqueueAction(std::move(download_action));
+
+    loop.PostTask(FROM_HERE,
+                  base::Bind(&TerminateEarlyTestStarter, &processor));
+    loop.Run();
+    EXPECT_FALSE(loop.PendingTasks());
+  }
+
+  // 1 or 0 chunks should have come through
+  const off_t resulting_file_size(utils::FileSize(temp_file.path()));
+  EXPECT_GE(resulting_file_size, 0);
+  if (resulting_file_size != 0)
+    EXPECT_EQ(kMockHttpFetcherChunkSize,
+              static_cast<size_t>(resulting_file_size));
+}
+
+}  // namespace
+
+TEST(DownloadActionTest, TerminateEarlyTest) {
+  TestTerminateEarly(true);
+}
+
+TEST(DownloadActionTest, TerminateEarlyNoDownloadDelegateTest) {
+  TestTerminateEarly(false);
+}
+
+class DownloadActionTestAction;
+
+template <>
+class ActionTraits<DownloadActionTestAction> {
+ public:
+  typedef InstallPlan OutputObjectType;
+  typedef InstallPlan InputObjectType;
+};
+
+// This is a simple Action class for testing.
+class DownloadActionTestAction : public Action<DownloadActionTestAction> {
+ public:
+  DownloadActionTestAction() = default;
+  typedef InstallPlan InputObjectType;
+  typedef InstallPlan OutputObjectType;
+  ActionPipe<InstallPlan>* in_pipe() { return in_pipe_.get(); }
+  ActionPipe<InstallPlan>* out_pipe() { return out_pipe_.get(); }
+  ActionProcessor* processor() { return processor_; }
+  void PerformAction() {
+    ASSERT_TRUE(HasInputObject());
+    EXPECT_TRUE(expected_input_object_ == GetInputObject());
+    ASSERT_TRUE(processor());
+    processor()->ActionComplete(this, ErrorCode::kSuccess);
+  }
+  static std::string StaticType() { return "DownloadActionTestAction"; }
+  string Type() const { return StaticType(); }
+  InstallPlan expected_input_object_;
+};
+
+namespace {
+// This class is an ActionProcessorDelegate that simply terminates the
+// run loop when the ActionProcessor has completed processing. It's used
+// only by the test PassObjectOutTest.
+class PassObjectOutTestProcessorDelegate : public ActionProcessorDelegate {
+ public:
+  void ProcessingDone(const ActionProcessor* processor,
+                      ErrorCode code) override {
+    brillo::MessageLoop::current()->BreakLoop();
+  }
+  void ActionCompleted(ActionProcessor* processor,
+                       AbstractAction* action,
+                       ErrorCode code) override {
+    if (action->Type() == DownloadActionTestAction::StaticType()) {
+      did_test_action_run_ = true;
+    }
+  }
+
+  bool did_test_action_run_ = false;
+};
+
+}  // namespace
+
+TEST(DownloadActionTest, PassObjectOutTest) {
+  FakeSystemState::CreateInstance();
+  brillo::FakeMessageLoop loop(nullptr);
+  loop.SetAsCurrent();
+
+  DirectFileWriter writer;
+  EXPECT_EQ(0, writer.Open("/dev/null", O_WRONLY | O_CREAT, 0));
+
+  // takes ownership of passed in HttpFetcher
+  InstallPlan install_plan;
+  install_plan.payloads.push_back({.size = 1});
+  EXPECT_TRUE(
+      HashCalculator::RawHashOfData({'x'}, &install_plan.payloads[0].hash));
+  auto feeder_action = std::make_unique<ObjectFeederAction<InstallPlan>>();
+  feeder_action->set_obj(install_plan);
+  MockPrefs prefs;
+  auto download_action =
+      std::make_unique<DownloadAction>(&prefs,
+                                       FakeSystemState::Get()->boot_control(),
+                                       FakeSystemState::Get()->hardware(),
+                                       new MockHttpFetcher("x", 1, nullptr),
+                                       false /* interactive */);
+  download_action->SetTestFileWriter(&writer);
+
+  auto test_action = std::make_unique<DownloadActionTestAction>();
+  test_action->expected_input_object_ = install_plan;
+  BondActions(feeder_action.get(), download_action.get());
+  BondActions(download_action.get(), test_action.get());
+
+  ActionProcessor processor;
+  PassObjectOutTestProcessorDelegate delegate;
+  processor.set_delegate(&delegate);
+  processor.EnqueueAction(std::move(feeder_action));
+  processor.EnqueueAction(std::move(download_action));
+  processor.EnqueueAction(std::move(test_action));
+
+  loop.PostTask(
+      FROM_HERE,
+      base::Bind(
+          [](ActionProcessor* processor) { processor->StartProcessing(); },
+          base::Unretained(&processor)));
+  loop.Run();
+  EXPECT_FALSE(loop.PendingTasks());
+
+  EXPECT_EQ(true, delegate.did_test_action_run_);
+}
+
+// Test fixture for P2P tests.
+class P2PDownloadActionTest : public testing::Test {
+ protected:
+  P2PDownloadActionTest() : start_at_offset_(0) {}
+
+  ~P2PDownloadActionTest() override {}
+
+  // Derived from testing::Test.
+  void SetUp() override {
+    loop_.SetAsCurrent();
+    FakeSystemState::CreateInstance();
+  }
+
+  // Derived from testing::Test.
+  void TearDown() override { EXPECT_FALSE(loop_.PendingTasks()); }
+
+  // To be called by tests to setup the download. The
+  // |starting_offset| parameter is for where to resume.
+  void SetupDownload(off_t starting_offset) {
+    start_at_offset_ = starting_offset;
+    // Prepare data 10 kB of data.
+    data_.clear();
+    for (unsigned int i = 0; i < 10 * 1000; i++)
+      data_ += 'a' + (i % 25);
+
+    // Setup p2p.
+    FakeP2PManagerConfiguration* test_conf = new FakeP2PManagerConfiguration();
+    p2p_manager_.reset(P2PManager::Construct(
+        test_conf, &fake_um_, "cros_au", 3, base::TimeDelta::FromDays(5)));
+  }
+
+  // To be called by tests to perform the download. The
+  // |use_p2p_to_share| parameter is used to indicate whether the
+  // payload should be shared via p2p.
+  void StartDownload(bool use_p2p_to_share) {
+    EXPECT_CALL(*FakeSystemState::Get()->mock_payload_state(),
+                GetUsingP2PForSharing())
+        .WillRepeatedly(Return(use_p2p_to_share));
+
+    ScopedTempFile output_temp_file;
+    TestDirectFileWriter writer;
+    EXPECT_EQ(
+        0, writer.Open(output_temp_file.path().c_str(), O_WRONLY | O_CREAT, 0));
+    InstallPlan install_plan;
+    install_plan.payloads.push_back(
+        {.size = data_.length(),
+         .hash = {'1', '2', '3', '4', 'h', 'a', 's', 'h'}});
+    auto feeder_action = std::make_unique<ObjectFeederAction<InstallPlan>>();
+    feeder_action->set_obj(install_plan);
+    MockPrefs prefs;
+    // Note that DownloadAction takes ownership of the passed in HttpFetcher.
+    auto download_action = std::make_unique<DownloadAction>(
+        &prefs,
+        FakeSystemState::Get()->boot_control(),
+        FakeSystemState::Get()->hardware(),
+        new MockHttpFetcher(data_.c_str(), data_.length(), nullptr),
+        false /* interactive */);
+    auto http_fetcher = download_action->http_fetcher();
+    download_action->SetTestFileWriter(&writer);
+    BondActions(feeder_action.get(), download_action.get());
+    delegate_.expected_data_ =
+        brillo::Blob(data_.begin() + start_at_offset_, data_.end());
+    delegate_.path_ = output_temp_file.path();
+    processor_.set_delegate(&delegate_);
+    processor_.EnqueueAction(std::move(feeder_action));
+    processor_.EnqueueAction(std::move(download_action));
+
+    loop_.PostTask(
+        FROM_HERE,
+        base::Bind(
+            [](P2PDownloadActionTest* action_test, HttpFetcher* http_fetcher) {
+              action_test->processor_.StartProcessing();
+              http_fetcher->SetOffset(action_test->start_at_offset_);
+            },
+            base::Unretained(this),
+            base::Unretained(http_fetcher)));
+    loop_.Run();
+  }
+
+  // Mainloop used to make StartDownload() synchronous.
+  brillo::FakeMessageLoop loop_{nullptr};
+
+  // Delegate that is passed to the ActionProcessor.
+  DownloadActionTestProcessorDelegate delegate_;
+
+  // The P2PManager used in the test.
+  unique_ptr<P2PManager> p2p_manager_;
+
+  // The ActionProcessor used for running the actions.
+  ActionProcessor processor_;
+
+  // The data being downloaded.
+  string data_;
+
+ private:
+  // The requested starting offset passed to SetupDownload().
+  off_t start_at_offset_;
+
+  chromeos_update_manager::FakeUpdateManager fake_um_;
+};
+
+TEST_F(P2PDownloadActionTest, IsWrittenTo) {
+  SetupDownload(0);     // starting_offset
+  StartDownload(true);  // use_p2p_to_share
+
+  // Check the p2p file and its content matches what was sent.
+  string file_id = delegate_.p2p_file_id_;
+  EXPECT_NE("", file_id);
+  EXPECT_EQ(static_cast<int>(data_.length()),
+            p2p_manager_->FileGetSize(file_id));
+  EXPECT_EQ(static_cast<int>(data_.length()),
+            p2p_manager_->FileGetExpectedSize(file_id));
+  string p2p_file_contents;
+  EXPECT_TRUE(
+      ReadFileToString(p2p_manager_->FileGetPath(file_id), &p2p_file_contents));
+  EXPECT_EQ(data_, p2p_file_contents);
+}
+
+TEST_F(P2PDownloadActionTest, DeleteIfHoleExists) {
+  SetupDownload(1000);  // starting_offset
+  StartDownload(true);  // use_p2p_to_share
+
+  // DownloadAction should convey that the file is not being shared.
+  // and that we don't have any p2p files.
+  EXPECT_EQ(delegate_.p2p_file_id_, "");
+  EXPECT_EQ(p2p_manager_->CountSharedFiles(), 0);
+}
+
+TEST_F(P2PDownloadActionTest, CanAppend) {
+  SetupDownload(1000);  // starting_offset
+
+  // Prepare the file with existing data before starting to write to
+  // it via DownloadAction.
+  string file_id = utils::CalculateP2PFileId(
+      {'1', '2', '3', '4', 'h', 'a', 's', 'h'}, data_.length());
+  ASSERT_TRUE(p2p_manager_->FileShare(file_id, data_.length()));
+  string existing_data;
+  for (unsigned int i = 0; i < 1000; i++)
+    existing_data += '0' + (i % 10);
+  ASSERT_EQ(
+      WriteFile(
+          p2p_manager_->FileGetPath(file_id), existing_data.c_str(), 1000),
+      1000);
+
+  StartDownload(true);  // use_p2p_to_share
+
+  // DownloadAction should convey the same file_id and the file should
+  // have the expected size.
+  EXPECT_EQ(delegate_.p2p_file_id_, file_id);
+  EXPECT_EQ(static_cast<ssize_t>(data_.length()),
+            p2p_manager_->FileGetSize(file_id));
+  EXPECT_EQ(static_cast<ssize_t>(data_.length()),
+            p2p_manager_->FileGetExpectedSize(file_id));
+  string p2p_file_contents;
+  // Check that the first 1000 bytes wasn't touched and that we
+  // appended the remaining as appropriate.
+  EXPECT_TRUE(
+      ReadFileToString(p2p_manager_->FileGetPath(file_id), &p2p_file_contents));
+  EXPECT_EQ(existing_data, p2p_file_contents.substr(0, 1000));
+  EXPECT_EQ(data_.substr(1000), p2p_file_contents.substr(1000));
+}
+
+TEST_F(P2PDownloadActionTest, DeletePartialP2PFileIfResumingWithoutP2P) {
+  SetupDownload(1000);  // starting_offset
+
+  // Prepare the file with all existing data before starting to write
+  // to it via DownloadAction.
+  string file_id = utils::CalculateP2PFileId(
+      {'1', '2', '3', '4', 'h', 'a', 's', 'h'}, data_.length());
+  ASSERT_TRUE(p2p_manager_->FileShare(file_id, data_.length()));
+  string existing_data;
+  for (unsigned int i = 0; i < 1000; i++)
+    existing_data += '0' + (i % 10);
+  ASSERT_EQ(
+      WriteFile(
+          p2p_manager_->FileGetPath(file_id), existing_data.c_str(), 1000),
+      1000);
+
+  // Check that the file is there.
+  EXPECT_EQ(1000, p2p_manager_->FileGetSize(file_id));
+  EXPECT_EQ(1, p2p_manager_->CountSharedFiles());
+
+  StartDownload(false);  // use_p2p_to_share
+
+  // DownloadAction should have deleted the p2p file. Check that it's gone.
+  EXPECT_EQ(-1, p2p_manager_->FileGetSize(file_id));
+  EXPECT_EQ(0, p2p_manager_->CountSharedFiles());
+}
+
+}  // namespace chromeos_update_engine