zircon/system/core/netsvc/test/paver-test.cc

// Copyright 2019 The Fuchsia 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 "paver.h"

#include <algorithm>

#include <fs/pseudo_dir.h>
#include <fs/service.h>
#include <fs/synchronous_vfs.h>
#include <fuchsia/paver/llcpp/fidl.h>
#include <lib/async-loop/cpp/loop.h>
#include <lib/async-loop/default.h>
#include <lib/driver-integration-test/fixture.h>
#include <lib/fidl-async/cpp/bind.h>
#include <lib/zx/channel.h>
#include <zircon/boot/netboot.h>
#include <zxtest/zxtest.h>

namespace {
constexpr char kFakeData[] = "lalala";
}

TEST(PaverTest, Constructor) { netsvc::Paver paver(zx::channel); }

TEST(PaverTest, GetSingleton) { ASSERT_NOT_NULL(netsvc::Paver::Get()); }

TEST(PaverTest, InitialInProgressFalse) {
  zx::channel chan;
  fbl::unique_fd fd;
  netsvc::Paver paver_(std::move(chan), std::move(fd));
  ASSERT_FALSE(paver_.InProgress());
}

TEST(PaverTest, InitialExitCodeValid) {
  zx::channel chan;
  fbl::unique_fd fd;
  netsvc::Paver paver_(std::move(chan), std::move(fd));
  ASSERT_OK(paver_.exit_code());
}

namespace {

enum class Command {
  kUnknown,
  kInitializeAbr,
  kQueryActiveConfiguration,
  kQueryConfigurationStatus,
  kSetConfigurationActive,
  kSetConfigurationUnbootable,
  kSetActiveConfigurationHealthy,
  kReadAsset,
  kWriteAsset,
  kWriteVolumes,
  kWriteBootloader,
  kWriteDataFile,
  kWipeVolumes,
  kInitializePartitionTables,
  kWipePartitionTables,
};

class FakePaver : public ::llcpp::fuchsia::paver::Paver::Interface {
 public:
  zx_status_t Connect(async_dispatcher_t* dispatcher, zx::channel request) {
    return fidl::Bind(dispatcher, std::move(request), this);
  }

  void InitializeAbr(InitializeAbrCompleter::Sync completer) {
    last_command_ = Command::kInitializeAbr;
    if (abr_supported_) {
      abr_initialized_ = true;
      completer.Reply(abr_supported_ ? ZX_OK : ZX_ERR_NOT_SUPPORTED);
    } else {
      completer.Reply(ZX_ERR_NOT_SUPPORTED);
    }
  }

  void QueryActiveConfiguration(QueryActiveConfigurationCompleter::Sync completer) {
    last_command_ = Command::kQueryActiveConfiguration;
    ::llcpp::fuchsia::paver::Paver_QueryActiveConfiguration_Result result;
    if (abr_supported_ && abr_initialized_) {
      ::llcpp::fuchsia::paver::Paver_QueryActiveConfiguration_Response response;
      response.configuration = ::llcpp::fuchsia::paver::Configuration::A;
      result.set_response(response);
    } else {
      result.set_err(ZX_ERR_NOT_SUPPORTED);
    }
    completer.Reply(std::move(result));
  }

  void QueryConfigurationStatus(::llcpp::fuchsia::paver::Configuration configuration,
                                QueryConfigurationStatusCompleter::Sync completer) {
    last_command_ = Command::kQueryConfigurationStatus;
    ::llcpp::fuchsia::paver::Paver_QueryConfigurationStatus_Result result;
    if (abr_supported_ && abr_initialized_) {
      ::llcpp::fuchsia::paver::Paver_QueryConfigurationStatus_Response response;
      response.status = ::llcpp::fuchsia::paver::ConfigurationStatus::HEALTHY;
    } else {
      result.set_err(ZX_ERR_NOT_SUPPORTED);
    }
    completer.Reply(std::move(result));
  }

  void SetConfigurationActive(::llcpp::fuchsia::paver::Configuration configuration,
                              SetConfigurationActiveCompleter::Sync completer) {
    last_command_ = Command::kSetConfigurationActive;
    zx_status_t status = ZX_ERR_NOT_SUPPORTED;
    if (abr_supported_ && abr_initialized_) {
      if (configuration == ::llcpp::fuchsia::paver::Configuration::A) {
        status = ZX_OK;
      } else {
        status = ZX_ERR_INVALID_ARGS;
      }
    }
    completer.Reply(status);
  }

  void SetConfigurationUnbootable(::llcpp::fuchsia::paver::Configuration configuration,
                                   SetConfigurationUnbootableCompleter::Sync completer) {
    last_command_ = Command::kSetConfigurationUnbootable;
    zx_status_t status = ZX_ERR_NOT_SUPPORTED;
    if (abr_supported_ && abr_initialized_) {
      if (configuration == ::llcpp::fuchsia::paver::Configuration::RECOVERY) {
        status = ZX_ERR_INVALID_ARGS;
      } else {
        status = ZX_OK;
      }
    }
    completer.Reply(status);
  }

  void SetActiveConfigurationHealthy(
      SetActiveConfigurationHealthyCompleter::Sync completer) {
    last_command_ = Command::kSetActiveConfigurationHealthy;
    completer.Reply(abr_supported_ && abr_initialized_ ? ZX_OK : ZX_ERR_NOT_SUPPORTED);
  }

  void ReadAsset(::llcpp::fuchsia::paver::Configuration configuration,
                 ::llcpp::fuchsia::paver::Asset asset, ReadAssetCompleter::Sync completer) {
    last_command_ = Command::kReadAsset;
    ::llcpp::fuchsia::paver::Paver_ReadAsset_Result result;
    result.set_err(ZX_ERR_NOT_SUPPORTED);
    completer.Reply(std::move(result));
  }

  void WriteAsset(::llcpp::fuchsia::paver::Configuration configuration,
                  ::llcpp::fuchsia::paver::Asset asset, ::llcpp::fuchsia::mem::Buffer payload,
                  WriteAssetCompleter::Sync completer) {
    last_command_ = Command::kWriteAsset;
    auto status = payload.size == expected_payload_size_ ? ZX_OK : ZX_ERR_INVALID_ARGS;
    completer.Reply(status);
  }

  void WriteVolumes(zx::channel payload_stream, WriteVolumesCompleter::Sync completer) {
    last_command_ = Command::kWriteVolumes;
    // Register VMO.
    zx::vmo vmo;
    auto status = zx::vmo::create(1024, 0, &vmo);
    if (status != ZX_OK) {
      completer.Reply(status);
      return;
    }
    ::llcpp::fuchsia::paver::PayloadStream::SyncClient stream(std::move(payload_stream));
    auto result = stream.RegisterVmo(std::move(vmo));
    status = result.ok() ? result.value().status : result.status();
    if (status != ZX_OK) {
      completer.Reply(status);
      return;
    }
    // Stream until EOF.
    status = [&]() {
      size_t data_transferred = 0;
      for (;;) {
        auto result = stream.ReadData();
        if (!result.ok()) {
          return result.status();
        }
        const auto& response = result.value();
        switch (response.result.which()) {
          case ::llcpp::fuchsia::paver::ReadResult::Tag::kErr:
            return response.result.err();
          case ::llcpp::fuchsia::paver::ReadResult::Tag::kEof:
            return data_transferred == expected_payload_size_ ? ZX_OK : ZX_ERR_INVALID_ARGS;
          case ::llcpp::fuchsia::paver::ReadResult::Tag::kInfo:
            data_transferred += response.result.info().size;
            continue;
          default:
            return ZX_ERR_INTERNAL;
        }
      }
    }();

    completer.Reply(status);
  }

  void WriteBootloader(::llcpp::fuchsia::mem::Buffer payload,
                       WriteBootloaderCompleter::Sync completer) {
    last_command_ = Command::kWriteBootloader;
    auto status = payload.size == expected_payload_size_ ? ZX_OK : ZX_ERR_INVALID_ARGS;
    completer.Reply(status);
  }

  void WriteDataFile(fidl::StringView filename, ::llcpp::fuchsia::mem::Buffer payload,
                     WriteDataFileCompleter::Sync completer) {
    last_command_ = Command::kWriteDataFile;
    auto status = payload.size == expected_payload_size_ ? ZX_OK : ZX_ERR_INVALID_ARGS;
    completer.Reply(status);
  }

  void WipeVolumes(zx::channel block_device, WipeVolumesCompleter::Sync completer) {
    last_command_ = Command::kWipeVolumes;
    auto status = ZX_OK;
    completer.Reply(status);
  }

  void InitializePartitionTables(zx::channel block_device,
                                 InitializePartitionTablesCompleter::Sync completer) {
    last_command_ = Command::kInitializePartitionTables;
    auto status = ZX_ERR_NOT_SUPPORTED;
    return completer.Reply(status);
  }

  void WipePartitionTables(zx::channel block_device, WipePartitionTablesCompleter::Sync completer) {
    last_command_ = Command::kWipePartitionTables;
    completer.Reply(ZX_OK);
  }

  Command last_command() { return last_command_; }
  void set_expected_payload_size(size_t size) { expected_payload_size_ = size; }
  void set_abr_supported(bool supported) { abr_supported_ = supported; }

 private:
  Command last_command_ = Command::kUnknown;
  size_t expected_payload_size_ = 0;
  bool abr_supported_ = false;
  bool abr_initialized_ = false;
};

class FakeSvc {
 public:
  explicit FakeSvc(async_dispatcher_t* dispatcher) : dispatcher_(dispatcher), vfs_(dispatcher) {
    auto root_dir = fbl::MakeRefCounted<fs::PseudoDir>();
    root_dir->AddEntry(::llcpp::fuchsia::paver::Paver::Name,
                       fbl::MakeRefCounted<fs::Service>([this](zx::channel request) {
                         return fake_paver_.Connect(dispatcher_, std::move(request));
                       }));

    zx::channel svc_remote;
    ASSERT_OK(zx::channel::create(0, &svc_local_, &svc_remote));

    vfs_.ServeDirectory(root_dir, std::move(svc_remote));
  }

  FakePaver& fake_paver() { return fake_paver_; }
  zx::channel& svc_chan() { return svc_local_; }

 private:
  async_dispatcher_t* dispatcher_;
  fs::SynchronousVfs vfs_;
  FakePaver fake_paver_;
  zx::channel svc_local_;
};

class FakeDev {
 public:
  FakeDev() {
    driver_integration_test::IsolatedDevmgr::Args args;
    args.driver_search_paths.push_back("/boot/driver");

    ASSERT_OK(driver_integration_test::IsolatedDevmgr::Create(&args, &devmgr_));
    fbl::unique_fd fd;
    ASSERT_OK(
        devmgr_integration_test::RecursiveWaitForFile(devmgr_.devfs_root(), "sys/platform", &fd));
    ASSERT_OK(
        devmgr_integration_test::RecursiveWaitForFile(devmgr_.devfs_root(), "misc/sysinfo", &fd));
  }

  driver_integration_test::IsolatedDevmgr devmgr_;
};

}  // namespace

class PaverTest : public zxtest::Test {
 protected:
  PaverTest()
      : loop_(&kAsyncLoopConfigNoAttachToCurrentThread),
        fake_svc_(loop_.dispatcher()),
        paver_(std::move(fake_svc_.svc_chan()), fake_dev_.devmgr_.devfs_root().duplicate()) {
    
    paver_.set_timeout(zx::msec(500));
    loop_.StartThread("paver-test-loop");
  }

  ~PaverTest() {
    // Need to make sure paver thread exits.
    Wait();
    loop_.Shutdown();
  }

  void Wait() {
    while (paver_.InProgress())
      continue;
  }

  async::Loop loop_;
  FakeSvc fake_svc_;
  FakeDev fake_dev_;
  netsvc::Paver paver_;
};

TEST_F(PaverTest, OpenWriteInvalidFile) {
  char invalid_file_name[32] = {};
  ASSERT_NE(paver_.OpenWrite(invalid_file_name, 0), TFTP_NO_ERROR);
  paver_.Close();
}

TEST_F(PaverTest, OpenWriteInvalidSize) {
  ASSERT_NE(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 0), TFTP_NO_ERROR);
}

TEST_F(PaverTest, OpenWriteValidFile) {
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  paver_.Close();
}

TEST_F(PaverTest, OpenTwice) {
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  ASSERT_NE(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  paver_.Close();
}

TEST_F(PaverTest, WriteWithoutOpen) {
  size_t size = sizeof(kFakeData);
  ASSERT_NE(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
}

TEST_F(PaverTest, WriteAfterClose) {
  size_t size = sizeof(kFakeData);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  paver_.Close();
  // TODO(surajmalhotra): Should we ensure this fails?
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
}

TEST_F(PaverTest, TimeoutNoWrites) {
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  paver_.Close();
  Wait();
  ASSERT_NE(paver_.exit_code(), ZX_OK);
}

TEST_F(PaverTest, TimeoutPartialWrite) {
  size_t size = sizeof(kFakeData);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_NE(paver_.exit_code(), ZX_OK);
}

TEST_F(PaverTest, WriteCompleteSingle) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteBootloader);
}

TEST_F(PaverTest, WriteCompleteManySmallWrites) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(1024);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 1024), TFTP_NO_ERROR);
  for (size_t offset = 0; offset < 1024; offset += sizeof(kFakeData)) {
    size = std::min(sizeof(kFakeData), 1024 - offset);
    ASSERT_EQ(paver_.Write(kFakeData, &size, offset), TFTP_NO_ERROR);
    ASSERT_EQ(size, std::min(sizeof(kFakeData), 1024 - offset));
  }
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
}

TEST_F(PaverTest, Overwrite) {
  size_t size = sizeof(kFakeData);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 2), TFTP_NO_ERROR);
  ASSERT_NE(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  paver_.Close();
  Wait();
  ASSERT_NE(paver_.exit_code(), ZX_OK);
}

TEST_F(PaverTest, CloseChannelBetweenWrites) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(2 * size);
  ASSERT_EQ(paver_.OpenWrite(NB_BOOTLOADER_FILENAME, 2 * size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  loop_.Shutdown();
  ASSERT_EQ(paver_.Write(kFakeData, &size, size), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_EQ(paver_.exit_code(), ZX_ERR_PEER_CLOSED);
}

TEST_F(PaverTest, WriteZirconA) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_ZIRCONA_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteVbMetaA) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_VBMETAA_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteZirconAWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_ZIRCONA_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteZirconBWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_ZIRCONB_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteZirconRWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_ZIRCONR_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteVbMetaAWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_VBMETAA_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kSetConfigurationActive);
}

TEST_F(PaverTest, WriteVbMetaBWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_VBMETAB_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteVbMetaRWithABRSupported) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_VBMETAR_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
}

TEST_F(PaverTest, WriteZirconAWithABRSupportedTwice) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_abr_supported(true);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  for (int i = 0 ; i < 2; i++) {
    ASSERT_EQ(paver_.OpenWrite(NB_ZIRCONA_FILENAME, size), TFTP_NO_ERROR);
    ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
    ASSERT_EQ(size, sizeof(kFakeData));
    paver_.Close();
    Wait();
    ASSERT_OK(paver_.exit_code());
    ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteAsset);
  }
}

TEST_F(PaverTest, WriteSshAuth) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_SSHAUTH_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteDataFile);
}

TEST_F(PaverTest, WriteFvm) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(size);
  ASSERT_EQ(paver_.OpenWrite(NB_FVM_FILENAME, size), TFTP_NO_ERROR);
  ASSERT_EQ(paver_.Write(kFakeData, &size, 0), TFTP_NO_ERROR);
  ASSERT_EQ(size, sizeof(kFakeData));
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteVolumes);
}

TEST_F(PaverTest, WriteFvmManySmallWrites) {
  size_t size = sizeof(kFakeData);
  fake_svc_.fake_paver().set_expected_payload_size(1024);
  ASSERT_EQ(paver_.OpenWrite(NB_FVM_FILENAME, 1024), TFTP_NO_ERROR);
  for (size_t offset = 0; offset < 1024; offset += sizeof(kFakeData)) {
    size = std::min(sizeof(kFakeData), 1024 - offset);
    ASSERT_EQ(paver_.Write(kFakeData, &size, offset), TFTP_NO_ERROR);
    ASSERT_EQ(size, std::min(sizeof(kFakeData), 1024 - offset));
  }
  paver_.Close();
  Wait();
  ASSERT_OK(paver_.exit_code());
  ASSERT_EQ(fake_svc_.fake_paver().last_command(), Command::kWriteVolumes);
}