Split payload application code into a subdirectory.

This patch splits from the main libupdate_engine code the part that
is strictly used to download and apply a payload into a new static
library, moving the code to subdirectories. The new library is divided
in two subdirectories: common/ and payload_consumer/, and should not
depend on other update_engine files outside those two subdirectories.
The main difference between those two is that the common/ tools are more
generic and not tied to the payload consumer process, but otherwise they
are both compiled together.

There are still dependencies from the new libpayload_consumer library
into the main directory files and DBus generated files. Those will be
addressed in follow up CLs.

Bug: 25197634
Test: FEATURES=test emerge-link update_engine; `mm` on Brillo.

Change-Id: Id8d0204ea573627e6e26ca9ea17b9592ca95bc23
diff --git a/payload_consumer/download_action_unittest.cc b/payload_consumer/download_action_unittest.cc
new file mode 100644
index 0000000..3bef196
--- /dev/null
+++ b/payload_consumer/download_action_unittest.cc
@@ -0,0 +1,634 @@
+//
+// 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 "update_engine/payload_consumer/download_action.h"
+
+#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/bind_lambda.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_http_fetcher.h"
+#include "update_engine/common/mock_prefs.h"
+#include "update_engine/common/test_utils.h"
+#include "update_engine/common/utils.h"
+#include "update_engine/fake_p2p_manager_configuration.h"
+#include "update_engine/fake_system_state.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 std::vector;
+using test_utils::ScopedTempFile;
+using testing::AtLeast;
+using testing::InSequence;
+using testing::Return;
+using testing::_;
+
+class DownloadActionTest : public ::testing::Test { };
+
+namespace {
+class DownloadActionDelegateMock : public DownloadActionDelegate {
+ public:
+  MOCK_METHOD1(SetDownloadStatus, void(bool active));
+  MOCK_METHOD2(BytesReceived, void(uint64_t bytes_received, uint64_t total));
+};
+
+class DownloadActionTestProcessorDelegate : public ActionProcessorDelegate {
+ public:
+  explicit DownloadActionTestProcessorDelegate(ErrorCode expected_code)
+      : processing_done_called_(false),
+        expected_code_(expected_code) {}
+  ~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 == DownloadAction::StaticType()) {
+      EXPECT_EQ(expected_code_, code);
+    } else {
+      EXPECT_EQ(ErrorCode::kSuccess, code);
+    }
+  }
+
+  string path_;
+  brillo::Blob expected_data_;
+  bool processing_done_called_;
+  ErrorCode expected_code_;
+};
+
+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) {
+  brillo::FakeMessageLoop loop(nullptr);
+  loop.SetAsCurrent();
+  FakeSystemState fake_system_state;
+
+  // TODO(adlr): see if we need a different file for build bots
+  ScopedTempFile output_temp_file;
+  TestDirectFileWriter writer;
+  EXPECT_EQ(0, writer.Open(output_temp_file.GetPath().c_str(),
+                           O_WRONLY | O_CREAT,
+                           0));
+  writer.set_fail_write(fail_write);
+
+  // We pull off the first byte from data and seek past it.
+  string hash = HashCalculator::HashOfBytes(&data[1], data.size() - 1);
+  uint64_t size = data.size();
+  InstallPlan install_plan(false,
+                           false,
+                           "",
+                           size,
+                           hash,
+                           0,
+                           "",
+                           "");
+  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.
+  fake_system_state.fake_boot_control()->SetSlotBootable(
+      install_plan.source_slot, true);
+  fake_system_state.fake_boot_control()->SetSlotBootable(
+      install_plan.target_slot, true);
+  ObjectFeederAction<InstallPlan> feeder_action;
+  feeder_action.set_obj(install_plan);
+  MockPrefs prefs;
+  MockHttpFetcher* http_fetcher = new MockHttpFetcher(data.data(),
+                                                      data.size(),
+                                                      nullptr);
+  // takes ownership of passed in HttpFetcher
+  DownloadAction download_action(&prefs, &fake_system_state, http_fetcher);
+  download_action.SetTestFileWriter(&writer);
+  BondActions(&feeder_action, &download_action);
+  DownloadActionDelegateMock download_delegate;
+  if (use_download_delegate) {
+    InSequence s;
+    download_action.set_delegate(&download_delegate);
+    EXPECT_CALL(download_delegate, SetDownloadStatus(true)).Times(1);
+    if (data.size() > kMockHttpFetcherChunkSize)
+      EXPECT_CALL(download_delegate,
+                  BytesReceived(1 + kMockHttpFetcherChunkSize, _));
+    EXPECT_CALL(download_delegate, BytesReceived(_, _)).Times(AtLeast(1));
+    EXPECT_CALL(download_delegate, SetDownloadStatus(false)).Times(1);
+  }
+  ErrorCode expected_code = ErrorCode::kSuccess;
+  if (fail_write > 0)
+    expected_code = ErrorCode::kDownloadWriteError;
+  DownloadActionTestProcessorDelegate delegate(expected_code);
+  delegate.expected_data_ = brillo::Blob(data.begin() + 1, data.end());
+  delegate.path_ = output_temp_file.GetPath();
+  ActionProcessor processor;
+  processor.set_delegate(&delegate);
+  processor.EnqueueAction(&feeder_action);
+  processor.EnqueueAction(&download_action);
+
+  loop.PostTask(FROM_HERE,
+                base::Bind(&StartProcessorInRunLoop, &processor, http_fetcher));
+  loop.Run();
+  EXPECT_FALSE(loop.PendingTasks());
+
+  EXPECT_TRUE(fake_system_state.fake_boot_control()->IsSlotBootable(
+      install_plan.source_slot));
+  EXPECT_FALSE(fake_system_state.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
+}
+
+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) {
+  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.GetPath().c_str(),
+                             O_WRONLY | O_CREAT,
+                             0));
+
+    // takes ownership of passed in HttpFetcher
+    ObjectFeederAction<InstallPlan> feeder_action;
+    InstallPlan install_plan(false, false, "", 0, "", 0, "", "");
+    feeder_action.set_obj(install_plan);
+    FakeSystemState fake_system_state_;
+    MockPrefs prefs;
+    DownloadAction download_action(&prefs, &fake_system_state_,
+                                   new MockHttpFetcher(data.data(),
+                                                       data.size(),
+                                                       nullptr));
+    download_action.SetTestFileWriter(&writer);
+    DownloadActionDelegateMock download_delegate;
+    if (use_download_delegate) {
+      InSequence s;
+      download_action.set_delegate(&download_delegate);
+      EXPECT_CALL(download_delegate, SetDownloadStatus(true)).Times(1);
+      EXPECT_CALL(download_delegate, SetDownloadStatus(false)).Times(1);
+    }
+    TerminateEarlyTestProcessorDelegate delegate;
+    ActionProcessor processor;
+    processor.set_delegate(&delegate);
+    processor.EnqueueAction(&feeder_action);
+    processor.EnqueueAction(&download_action);
+    BondActions(&feeder_action, &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.GetPath()));
+  EXPECT_GE(resulting_file_size, 0);
+  if (resulting_file_size != 0)
+    EXPECT_EQ(kMockHttpFetcherChunkSize, 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() : did_run_(false) {}
+  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() {
+    did_run_ = true;
+    ASSERT_TRUE(HasInputObject());
+    EXPECT_TRUE(expected_input_object_ == GetInputObject());
+    ASSERT_TRUE(processor());
+    processor()->ActionComplete(this, ErrorCode::kSuccess);
+  }
+  string Type() const { return "DownloadActionTestAction"; }
+  InstallPlan expected_input_object_;
+  bool did_run_;
+};
+
+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) {
+    brillo::MessageLoop::current()->BreakLoop();
+  }
+};
+
+}  // namespace
+
+TEST(DownloadActionTest, PassObjectOutTest) {
+  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(false,
+                           false,
+                           "",
+                           1,
+                           HashCalculator::HashOfString("x"),
+                           0,
+                           "",
+                           "");
+  ObjectFeederAction<InstallPlan> feeder_action;
+  feeder_action.set_obj(install_plan);
+  MockPrefs prefs;
+  FakeSystemState fake_system_state_;
+  DownloadAction download_action(&prefs, &fake_system_state_,
+                                 new MockHttpFetcher("x", 1, nullptr));
+  download_action.SetTestFileWriter(&writer);
+
+  DownloadActionTestAction test_action;
+  test_action.expected_input_object_ = install_plan;
+  BondActions(&feeder_action, &download_action);
+  BondActions(&download_action, &test_action);
+
+  ActionProcessor processor;
+  PassObjectOutTestProcessorDelegate delegate;
+  processor.set_delegate(&delegate);
+  processor.EnqueueAction(&feeder_action);
+  processor.EnqueueAction(&download_action);
+  processor.EnqueueAction(&test_action);
+
+  loop.PostTask(FROM_HERE,
+                base::Bind([&processor] { processor.StartProcessing(); }));
+  loop.Run();
+  EXPECT_FALSE(loop.PendingTasks());
+
+  EXPECT_EQ(true, test_action.did_run_);
+}
+
+// Test fixture for P2P tests.
+class P2PDownloadActionTest : public testing::Test {
+ protected:
+  P2PDownloadActionTest()
+    : start_at_offset_(0),
+      fake_um_(fake_system_state_.fake_clock()) {}
+
+  ~P2PDownloadActionTest() override {}
+
+  // Derived from testing::Test.
+  void SetUp() override {
+    loop_.SetAsCurrent();
+  }
+
+  // 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, nullptr, &fake_um_, "cros_au", 3,
+        base::TimeDelta::FromDays(5)));
+    fake_system_state_.set_p2p_manager(p2p_manager_.get());
+  }
+
+  // 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(*fake_system_state_.mock_payload_state(),
+                GetUsingP2PForSharing())
+        .WillRepeatedly(Return(use_p2p_to_share));
+
+    ScopedTempFile output_temp_file;
+    TestDirectFileWriter writer;
+    EXPECT_EQ(0, writer.Open(output_temp_file.GetPath().c_str(),
+                             O_WRONLY | O_CREAT,
+                             0));
+    InstallPlan install_plan(false,
+                             false,
+                             "",
+                             data_.length(),
+                             "1234hash",
+                             0,
+                             "",
+                             "");
+    ObjectFeederAction<InstallPlan> feeder_action;
+    feeder_action.set_obj(install_plan);
+    MockPrefs prefs;
+    http_fetcher_ = new MockHttpFetcher(data_.c_str(),
+                                        data_.length(),
+                                        nullptr);
+    // Note that DownloadAction takes ownership of the passed in HttpFetcher.
+    download_action_.reset(new DownloadAction(&prefs, &fake_system_state_,
+                                              http_fetcher_));
+    download_action_->SetTestFileWriter(&writer);
+    BondActions(&feeder_action, download_action_.get());
+    DownloadActionTestProcessorDelegate delegate(ErrorCode::kSuccess);
+    delegate.expected_data_ = brillo::Blob(data_.begin() + start_at_offset_,
+                                           data_.end());
+    delegate.path_ = output_temp_file.GetPath();
+    processor_.set_delegate(&delegate);
+    processor_.EnqueueAction(&feeder_action);
+    processor_.EnqueueAction(download_action_.get());
+
+    loop_.PostTask(FROM_HERE, base::Bind(
+        &P2PDownloadActionTest::StartProcessorInRunLoopForP2P,
+        base::Unretained(this)));
+    loop_.Run();
+  }
+
+  // Mainloop used to make StartDownload() synchronous.
+  brillo::FakeMessageLoop loop_{nullptr};
+
+  // The DownloadAction instance under test.
+  unique_ptr<DownloadAction> download_action_;
+
+  // The HttpFetcher used in the test.
+  MockHttpFetcher* http_fetcher_;
+
+  // The P2PManager used in the test.
+  unique_ptr<P2PManager> p2p_manager_;
+
+  // The ActionProcessor used for running the actions.
+  ActionProcessor processor_;
+
+  // A fake system state.
+  FakeSystemState fake_system_state_;
+
+  // The data being downloaded.
+  string data_;
+
+ private:
+  // Callback used in StartDownload() method.
+  void StartProcessorInRunLoopForP2P() {
+    processor_.StartProcessing();
+    http_fetcher_->SetOffset(start_at_offset_);
+  }
+
+  // The requested starting offset passed to SetupDownload().
+  off_t start_at_offset_;
+
+  chromeos_update_manager::FakeUpdateManager fake_um_;
+};
+
+TEST_F(P2PDownloadActionTest, IsWrittenTo) {
+  if (!test_utils::IsXAttrSupported(FilePath("/tmp"))) {
+    LOG(WARNING) << "Skipping test because /tmp does not support xattr. "
+                 << "Please update your system to support this feature.";
+    return;
+  }
+
+  SetupDownload(0);     // starting_offset
+  StartDownload(true);  // use_p2p_to_share
+
+  // Check the p2p file and its content matches what was sent.
+  string file_id = download_action_->p2p_file_id();
+  EXPECT_NE("", file_id);
+  EXPECT_EQ(data_.length(), p2p_manager_->FileGetSize(file_id));
+  EXPECT_EQ(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) {
+  if (!test_utils::IsXAttrSupported(FilePath("/tmp"))) {
+    LOG(WARNING) << "Skipping test because /tmp does not support xattr. "
+                 << "Please update your system to support this feature.";
+    return;
+  }
+
+  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(download_action_->p2p_file_id(), "");
+  EXPECT_EQ(p2p_manager_->CountSharedFiles(), 0);
+}
+
+TEST_F(P2PDownloadActionTest, CanAppend) {
+  if (!test_utils::IsXAttrSupported(FilePath("/tmp"))) {
+    LOG(WARNING) << "Skipping test because /tmp does not support xattr. "
+                 << "Please update your system to support this feature.";
+    return;
+  }
+
+  SetupDownload(1000);  // starting_offset
+
+  // Prepare the file with existing data before starting to write to
+  // it via DownloadAction.
+  string file_id = utils::CalculateP2PFileId("1234hash", 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(download_action_->p2p_file_id(), file_id);
+  EXPECT_EQ(p2p_manager_->FileGetSize(file_id), data_.length());
+  EXPECT_EQ(p2p_manager_->FileGetExpectedSize(file_id), data_.length());
+  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) {
+  if (!test_utils::IsXAttrSupported(FilePath("/tmp"))) {
+    LOG(WARNING) << "Skipping test because /tmp does not support xattr. "
+                 << "Please update your system to support this feature.";
+    return;
+  }
+
+  SetupDownload(1000);  // starting_offset
+
+  // Prepare the file with all existing data before starting to write
+  // to it via DownloadAction.
+  string file_id = utils::CalculateP2PFileId("1234hash", 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(p2p_manager_->FileGetSize(file_id), 1000);
+  EXPECT_EQ(p2p_manager_->CountSharedFiles(), 1);
+
+  StartDownload(false);  // use_p2p_to_share
+
+  // DownloadAction should have deleted the p2p file. Check that it's gone.
+  EXPECT_EQ(p2p_manager_->FileGetSize(file_id), -1);
+  EXPECT_EQ(p2p_manager_->CountSharedFiles(), 0);
+}
+
+}  // namespace chromeos_update_engine