Adds a new class HttpCache::Writers for multiple cache transactions reading from the network.

net/http/http_cache_writers_unittest.cc

Index: net/http/http_cache_writers_unittest.cc
diff --git a/net/http/http_cache_writers_unittest.cc b/net/http/http_cache_writers_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..28bb83437f6eccd3db34a28f2f29989902036cf7
--- /dev/null
+++ b/net/http/http_cache_writers_unittest.cc
@@ -0,0 +1,664 @@
+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/http/http_cache_writers.h"
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/run_loop.h"
+#include "net/http/http_cache.h"
+#include "net/http/http_cache_transaction.h"
+#include "net/http/http_transaction.h"
+#include "net/http/http_transaction_test_util.h"
+#include "net/http/mock_http_cache.h"
+#include "net/test/gtest_util.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using net::test::IsError;
+using net::test::IsOk;
+
+namespace net {
+
+class MockHttpCacheTransaction : public HttpCache::Transaction {
+  typedef WebSocketHandshakeStreamBase::CreateHelper CreateHelper;
+
+ public:
+  MockHttpCacheTransaction(RequestPriority priority, HttpCache* cache)
+      : HttpCache::Transaction(priority, cache){};
+  ~MockHttpCacheTransaction() override{};
+
+  // HttpCache::Transaction:
+
+  int Start(const HttpRequestInfo* request,
+            const CompletionCallback& callback,
+            const NetLogWithSource& net_log) override {
+    return OK;
+  }
+
+  int RestartIgnoringLastError(const CompletionCallback& callback) override {
+    return OK;
+  }
+
+  int RestartWithCertificate(scoped_refptr<X509Certificate> client_cert,
+                             scoped_refptr<SSLPrivateKey> client_private_key,
+                             const CompletionCallback& callback) override {
+    return OK;
+  }
+
+  int RestartWithAuth(const AuthCredentials& credentials,
+                      const CompletionCallback& callback) override {
+    return OK;
+  }
+
+  bool IsReadyToRestartForAuth() override { return true; }
+
+  int Read(IOBuffer* buf,
+           int buf_len,
+           const CompletionCallback& callback) override {
+    return OK;
+  }
+
+  void PopulateNetErrorDetails(NetErrorDetails* details) const override {}
+
+  void StopCaching() override {}
+
+  bool GetFullRequestHeaders(HttpRequestHeaders* headers) const override {
+    return true;
+  }
+
+  int64_t GetTotalReceivedBytes() const override { return OK; }
+
+  int64_t GetTotalSentBytes() const override { return OK; }
+
+  void DoneReading() override {}
+
+  const HttpResponseInfo* GetResponseInfo() const override { return nullptr; }
+
+  LoadState GetLoadState() const override { return LOAD_STATE_IDLE; }
+
+  void SetQuicServerInfo(QuicServerInfo* quic_server_info) override {}
+
+  bool GetLoadTimingInfo(LoadTimingInfo* load_timing_info) const override {
+    return true;
+  }
+
+  bool GetRemoteEndpoint(IPEndPoint* endpoint) const override { return true; }
+
+  void SetWebSocketHandshakeStreamCreateHelper(
+      CreateHelper* create_helper) override {}
+
+  void SetBeforeNetworkStartCallback(
+      const BeforeNetworkStartCallback& callback) override {}
+
+  void SetBeforeHeadersSentCallback(
+      const BeforeHeadersSentCallback& callback) override {}
+
+  int ResumeNetworkStart() override { return OK; }
+
+  void GetConnectionAttempts(ConnectionAttempts* out) const override {}
+
+  CreateHelper* websocket_handshake_stream_create_helper() { return nullptr; }
+};
+
+class WritersTest : public testing::Test {
+ public:
+  enum class DeleteTransactionType { NONE, ACTIVE, WAITING, IDLE };
+
+  WritersTest() : disk_entry_(nullptr), request_(kSimpleGET_Transaction) {}
+
+  ~WritersTest() override {
+    if (disk_entry_)
+      disk_entry_->Close();
+  }
+
+  void CreateWriters(const std::string& url) {
+    cache_.CreateBackendEntry(kSimpleGET_Transaction.url, &disk_entry_,
+                              nullptr);
+    writers_ = base::MakeUnique<HttpCache::Writers>(disk_entry_);
+  }
+
+  std::unique_ptr<HttpTransaction> CreateNetworkTransaction() {
+    std::unique_ptr<HttpTransaction> transaction;
+    MockNetworkLayer* network_layer = cache_.network_layer();
+    network_layer->CreateTransaction(DEFAULT_PRIORITY, &transaction);
+    return transaction;
+  }
+
+  void CreateWritersAddTransaction(bool is_exclusive = false) {
+    TestCompletionCallback callback;
+
+    // Create and Start a mock network transaction.
+    std::unique_ptr<HttpTransaction> network_transaction;
+    network_transaction = CreateNetworkTransaction();
+    network_transaction->Start(&request_, callback.callback(),
+                               NetLogWithSource());
+    base::RunLoop().RunUntilIdle();
+
+    // Create a mock cache transaction.
+    std::unique_ptr<MockHttpCacheTransaction> transaction =
+        base::MakeUnique<MockHttpCacheTransaction>(DEFAULT_PRIORITY,
+                                                   cache_.http_cache());
+
+    CreateWriters(kSimpleGET_Transaction.url);
+    EXPECT_TRUE(writers_->IsEmpty());
+    writers_->AddTransaction(transaction.get(), std::move(network_transaction),
+                             is_exclusive);
+    EXPECT_TRUE(writers_->HasTransaction(transaction.get()));
+    transactions_.push_back(std::move(transaction));
+  }
+
+  void CreateWritersAddTransactionPriority(net::RequestPriority priority,
+                                           bool is_exclusive = false) {
+    CreateWritersAddTransaction(is_exclusive);
+    MockHttpCacheTransaction* transaction = transactions_.begin()->get();
+    transaction->SetPriority(priority);
+  }
+
+  void AddTransactionToExistingWriters() {
+    EXPECT_TRUE(writers_);
+
+    // Create a mock cache transaction.
+    std::unique_ptr<MockHttpCacheTransaction> transaction =
+        base::MakeUnique<MockHttpCacheTransaction>(DEFAULT_PRIORITY,
+                                                   cache_.http_cache());
+
+    writers_->AddTransaction(transaction.get(), nullptr, false);
+    transactions_.push_back(std::move(transaction));
+  }
+
+  int Read(std::string* result) {
+    EXPECT_TRUE(transactions_.size() >= (size_t)1);
+    MockHttpCacheTransaction* transaction = transactions_.begin()->get();
+    TestCompletionCallback callback;
+
+    std::string content;
+    int rv = 0;
+    do {
+      scoped_refptr<IOBuffer> buf(new IOBuffer(kDefaultBufferSize));
+      rv = writers_->Read(buf.get(), kDefaultBufferSize, callback.callback(),
+                          transaction);
+      if (rv == ERR_IO_PENDING) {
+        rv = callback.WaitForResult();
+        base::RunLoop().RunUntilIdle();
+      }
+
+      if (rv > 0)
+        content.append(buf->data(), rv);
+      else if (rv < 0)
+        return rv;
+    } while (rv > 0);
+
+    result->swap(content);
+    return OK;
+  }
+
+  void ReadVerifyTwoDifferentBufferLengths(
+      const std::vector<int>& buffer_lengths) {
+    EXPECT_EQ(2u, buffer_lengths.size());
+    EXPECT_EQ(2u, transactions_.size());
+
+    std::vector<std::string> results(buffer_lengths.size());
+
+    // Check only the 1st Read and not the complete response because the smaller
+    // buffer transaction will need to read the remaining response from the
+    // cache which will be tested when integrated with MockHttpCacheTransaction
+    // layer.
+
+    int rv = 0;
+
+    std::vector<scoped_refptr<IOBuffer>> bufs;
+    for (auto buffer_length : buffer_lengths)
+      bufs.push_back(new IOBuffer(buffer_length));
+
+    std::vector<TestCompletionCallback> callbacks(buffer_lengths.size());
+
+    // Multiple transactions should be able to read with different sized
+    // buffers.
+    for (size_t i = 0; i < transactions_.size(); i++) {
+      rv = writers_->Read(bufs[i].get(), buffer_lengths[i],
+                          callbacks[i].callback(), transactions_[i].get());
+      EXPECT_EQ(ERR_IO_PENDING, rv);  // Since the default is asynchronous.
+    }
+
+    // If first buffer is smaller, then the second one will only read the
+    // smaller length as well.
+    std::vector<int> expected_lengths = {buffer_lengths[0],
+                                         buffer_lengths[0] < buffer_lengths[1]
+                                             ? buffer_lengths[0]
+                                             : buffer_lengths[1]};
+
+    for (size_t i = 0; i < callbacks.size(); i++) {
+      rv = callbacks[i].WaitForResult();
+      EXPECT_EQ(expected_lengths[i], rv);
+      results[i].append(bufs[i]->data(), expected_lengths[i]);
+    }
+
+    EXPECT_EQ(results[0].substr(0, expected_lengths[1]), results[1]);
+
+    std::string expected(kSimpleGET_Transaction.data);
+    EXPECT_EQ(expected.substr(0, expected_lengths[1]), results[1]);
+  }
+
+  // Each transaction invokes Read simultaneously. If |deleteType| is not NONE,
+  // then it deletes the transaction of given type during the read process.
+  void ReadAllDeleteTransaction(DeleteTransactionType deleteType) {
+    EXPECT_TRUE(transactions_.size() >= 3u);
+
+    unsigned int delete_index = std::numeric_limits<unsigned int>::max();
+    switch (deleteType) {
+      case DeleteTransactionType::NONE:
+        break;
+      case DeleteTransactionType::ACTIVE:
+        delete_index = 0;
+        break;
+      case DeleteTransactionType::WAITING:
+        delete_index = 1;
+        break;
+      case DeleteTransactionType::IDLE:
+        delete_index = 2;
+        break;
+    }
+
+    std::vector<std::string> results(transactions_.size());
+    int rv = 0;
+    bool first_iter = true;
+    do {
+      std::vector<scoped_refptr<IOBuffer>> bufs;
+      std::vector<TestCompletionCallback> callbacks(transactions_.size());
+
+      for (size_t i = 0; i < transactions_.size(); i++) {
+        bufs.push_back(new IOBuffer(kDefaultBufferSize));
+
+        // If we have deleted a transaction in the first iteration, then do not
+        // invoke Read on it, in subsequent iterations.
+        if (!first_iter && deleteType != DeleteTransactionType::NONE &&
+            i == delete_index)
+          continue;
+
+        // For it to be an idle transaction, do not invoke Read.
+        if (deleteType == DeleteTransactionType::IDLE && i == delete_index)
+          continue;
+
+        rv = writers_->Read(bufs[i].get(), kDefaultBufferSize,
+                            callbacks[i].callback(), transactions_[i].get());
+        EXPECT_EQ(ERR_IO_PENDING, rv);  // Since the default is asynchronous.
+      }
+
+      if (first_iter && deleteType != DeleteTransactionType::NONE) {
+        writers_->RemoveTransaction(transactions_.at(delete_index).get());
+      }
+
+      std::vector<int> rvs;
+      for (size_t i = 0; i < callbacks.size(); i++) {
+        if (i == delete_index && deleteType != DeleteTransactionType::NONE)
+          continue;
+        rv = callbacks[i].WaitForResult();
+        rvs.push_back(rv);
+      }
+
+      // Verify all transactions should read the same length buffer.
+      for (size_t i = 1; i < rvs.size(); i++) {
+        ASSERT_EQ(rvs[i - 1], rvs[i]);
+      }
+
+      if (rv > 0) {
+        for (size_t i = 0; i < results.size(); i++) {
+          if (i == delete_index && deleteType != DeleteTransactionType::NONE &&
+              deleteType != DeleteTransactionType::ACTIVE) {
+            continue;
+          }
+          results.at(i).append(bufs[i]->data(), rv);
+        }
+      }
+      first_iter = false;
+    } while (rv > 0);
+
+    for (size_t i = 0; i < results.size(); i++) {
+      if (i == delete_index && deleteType != DeleteTransactionType::NONE &&
+          deleteType != DeleteTransactionType::ACTIVE) {
+        continue;
+      }
+      EXPECT_EQ(kSimpleGET_Transaction.data, results[i]);
+    }
+
+    EXPECT_EQ(OK, rv);
+  }
+
+  void ReadAll() { ReadAllDeleteTransaction(DeleteTransactionType::NONE); }
+
+  int ReadCacheWriteFailure(std::vector<std::string>* results) {
+    int rv = 0;
+    int active_transaction_rv = 0;
+    bool first_iter = true;
+    do {
+      std::vector<scoped_refptr<IOBuffer>> bufs;
+      std::vector<TestCompletionCallback> callbacks(results->size());
+
+      // Fail the request.
+      cache_.disk_cache()->set_soft_failures(true);
+
+      // We have to open the entry again to propagate the failure flag.
+      disk_cache::Entry* en;
+      cache_.OpenBackendEntry(kSimpleGET_Transaction.url, &en);
+      en->Close();
+
+      for (size_t i = 0; i < transactions_.size(); i++) {
+        bufs.push_back(new IOBuffer(30));
+
+        if (!first_iter && i > 0)
+          break;
+        rv = writers_->Read(bufs[i].get(), 30, callbacks[i].callback(),
+                            transactions_[i].get());
+        EXPECT_EQ(ERR_IO_PENDING, rv);  // Since the default is asynchronous.
+      }
+
+      for (size_t i = 0; i < callbacks.size(); i++) {
+        // Only active transaction should succeed.
+        if (i == 0) {
+          active_transaction_rv = callbacks[i].WaitForResult();
+          EXPECT_TRUE(active_transaction_rv >= 0);
+          results->at(0).append(bufs[i]->data(), active_transaction_rv);
+        } else if (first_iter) {
+          rv = callbacks[i].WaitForResult();
+          EXPECT_EQ(ERR_CACHE_WRITE_FAILURE, rv);
+        }
+      }
+
+      first_iter = false;
+    } while (active_transaction_rv > 0);
+
+    return active_transaction_rv;
+  }
+
+  int ReadNetworkFailure(std::vector<std::string>* results, Error error) {
+    int rv = 0;
+    std::vector<scoped_refptr<IOBuffer>> bufs;
+    std::vector<TestCompletionCallback> callbacks(results->size());
+
+    for (size_t i = 0; i < transactions_.size(); i++) {
+      bufs.push_back(new IOBuffer(30));
+
+      rv = writers_->Read(bufs[i].get(), 30, callbacks[i].callback(),
+                          transactions_[i].get());
+      EXPECT_EQ(ERR_IO_PENDING, rv);  // Since the default is asynchronous.
+    }
+
+    for (auto& callback : callbacks) {
+      rv = callback.WaitForResult();
+      EXPECT_EQ(error, rv);
+    }
+
+    return error;
+  }
+
+  bool StopCaching() {
+    MockHttpCacheTransaction* transaction = transactions_.begin()->get();
+    EXPECT_TRUE(transaction);
+    return writers_->StopCaching(transaction);
+  }
+
+  void RemoveFirstTransaction() {
+    MockHttpCacheTransaction* transaction = transactions_.begin()->get();
+    EXPECT_TRUE(transaction);
+    writers_->RemoveTransaction(transaction);
+  }
+
+  void UpdateAndVerifyPriority(RequestPriority priority) {
+    writers_->UpdatePriority();
+    EXPECT_EQ(priority, writers_->priority_);
+  }
+
+  MockHttpCache cache_;
+  std::unique_ptr<HttpCache::Writers> writers_;
+  disk_cache::Entry* disk_entry_;
+
+  // Should be before transactions_ since it is accessed in the network
+  // transaction's destructor.
+  MockHttpRequest request_;
+
+  static const int kDefaultBufferSize = 256;
+
+  std::vector<std::unique_ptr<MockHttpCacheTransaction>> transactions_;
+};
+
+// Tests successful addition of a transaction.
+TEST_F(WritersTest, AddTransaction) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+}
+
+// Tests successful addition of multiple transactions.
+TEST_F(WritersTest, AddManyTransactions) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  for (int i = 0; i < 5; i++)
+    AddTransactionToExistingWriters();
+
+  EXPECT_EQ(6, writers_->CountTransactionsForTesting());
+}
+
+// Tests that CanAddWriters should return false if it is writing exclusively.
+TEST_F(WritersTest, AddTransactionsExclusive) {
+  CreateWritersAddTransaction(true /* is_exclusive */);
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_FALSE(writers_->CanAddWriters());
+}
+
+// Tests StopCaching should not stop caching if there are multiple writers.
+TEST_F(WritersTest, StopCachingMultipleWriters) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+
+  EXPECT_FALSE(StopCaching());
+  EXPECT_TRUE(writers_->CanAddWriters());
+}
+
+// Tests StopCaching should stop caching if there is a single writer.
+TEST_F(WritersTest, StopCaching) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(StopCaching());
+  EXPECT_FALSE(writers_->CanAddWriters());
+}
+
+// Tests removing of an idle transaction and change in priority.
+TEST_F(WritersTest, RemoveIdleTransaction) {
+  CreateWritersAddTransactionPriority(HIGHEST);
+  UpdateAndVerifyPriority(HIGHEST);
+
+  AddTransactionToExistingWriters();
+  UpdateAndVerifyPriority(HIGHEST);
+
+  EXPECT_FALSE(writers_->IsEmpty());
+  EXPECT_EQ(2, writers_->CountTransactionsForTesting());
+
+  RemoveFirstTransaction();
+  EXPECT_EQ(1, writers_->CountTransactionsForTesting());
+
+  UpdateAndVerifyPriority(DEFAULT_PRIORITY);
+}
+
+// Tests that Read is successful.
+TEST_F(WritersTest, Read) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  std::string content;
+  int rv = Read(&content);
+
+  EXPECT_THAT(rv, IsOk());
+  std::string expected(kSimpleGET_Transaction.data);
+  EXPECT_EQ(expected, content);
+}
+
+// Tests that multiple transactions can read the same data simultaneously.
+TEST_F(WritersTest, ReadMultiple) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  ReadAll();
+}
+
+// Tests that multiple transactions can read the same data simultaneously.
+TEST_F(WritersTest, ReadMultipleDifferentBufferSizes) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+
+  std::vector<int> buffer_lengths{20, 10};
+  ReadVerifyTwoDifferentBufferLengths(buffer_lengths);
+}
+
+// Same as above but tests the first transaction having smaller buffer size
+// than the next.
+TEST_F(WritersTest, ReadMultipleDifferentBufferSizes1) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+
+  std::vector<int> buffer_lengths{10, 20};
+  ReadVerifyTwoDifferentBufferLengths(buffer_lengths);
+}
+
+// Tests that ongoing Read completes even when active transaction is deleted
+// mid-read. Any transactions waiting should be able to get the read buffer.
+TEST_F(WritersTest, ReadMultipleDeleteActiveTransaction) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  ReadAllDeleteTransaction(DeleteTransactionType::ACTIVE);
+}
+
+// Tests that removing a waiting for read transaction does not impact other
+// transactions.
+TEST_F(WritersTest, ReadMultipleDeleteWaitingTransaction) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  std::vector<std::string> contents(4);
+  ReadAllDeleteTransaction(DeleteTransactionType::WAITING);
+}
+
+// Tests that removing an idle transaction does not impact other transactions.
+TEST_F(WritersTest, ReadMultipleDeleteIdleTransaction) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  std::vector<std::string> contents(3);
+  ReadAllDeleteTransaction(DeleteTransactionType::IDLE);
+}
+
+// Tests cache write failure.
+TEST_F(WritersTest, ReadMultipleCacheWriteFailed) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  std::vector<std::string> contents(3);
+  int rv = ReadCacheWriteFailure(&contents);
+
+  EXPECT_THAT(rv, IsOk());
+  std::string expected(kSimpleGET_Transaction.data);
+
+  // Only active_transaction_ should succeed.
+  EXPECT_EQ(expected, contents.at(0));
+
+  // No new transactions should now be added.
+  EXPECT_FALSE(writers_->CanAddWriters());
+}
+
+// Tests that network read failure fails all transactions: active, waiting and
+// idle.
+TEST_F(WritersTest, ReadMultipleNetworkReadFailed) {
+  ScopedMockTransaction transaction(kSimpleGET_Transaction);
+  transaction.read_return_code = ERR_INTERNET_DISCONNECTED;
+  MockHttpRequest request(transaction);
+  request_ = request;
+
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  std::vector<std::string> contents(3);
+  int rv = ReadNetworkFailure(&contents, ERR_INTERNET_DISCONNECTED);
+
+  EXPECT_EQ(ERR_INTERNET_DISCONNECTED, rv);
+}
+
+// Tests moving idle writers to readers.
+TEST_F(WritersTest, MoveIdleWritersToReaders) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_TRUE(writers_->CanAddWriters());
+  AddTransactionToExistingWriters();
+  AddTransactionToExistingWriters();
+
+  EXPECT_FALSE(writers_->IsEmpty());
+  writers_->RemoveAllIdleWriters();
+  EXPECT_TRUE(writers_->IsEmpty());
+}
+
+// Tests GetWriterLoadState.
+TEST_F(WritersTest, GetWriterLoadState) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  EXPECT_EQ(LOAD_STATE_IDLE, writers_->GetWriterLoadState());
+}
+
+// Tests truncating the entry via Writers.
+TEST_F(WritersTest, TruncateEntry) {
+  CreateWritersAddTransaction();
+  EXPECT_FALSE(writers_->IsEmpty());
+
+  std::string content;
+  int rv = Read(&content);
+
+  EXPECT_THAT(rv, IsOk());
+  std::string expected(kSimpleGET_Transaction.data);
+  EXPECT_EQ(expected, content);
+
+  writers_->TruncateEntry();
+  base::RunLoop().RunUntilIdle();
+  EXPECT_TRUE(writers_->IsTruncatedForTesting());
+}
+
+}  // namespace net