folly/test/SingletonTest.cpp

   1 /*
   2  * Copyright 2016 Facebook, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  *   http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <thread>
  18
  19 #include <folly/Singleton.h>
  20 #include <folly/Subprocess.h>
  21 #include <folly/experimental/io/FsUtil.h>
  22 #include <folly/io/async/EventBase.h>
  23 #include <folly/portability/GMock.h>
  24 #include <folly/portability/GTest.h>
  25 #include <folly/test/SingletonTestStructs.h>
  26
  27 #include <glog/logging.h>
  28 #include <boost/thread/barrier.hpp>
  29
  30 using namespace folly;
  31
  32 TEST(Singleton, MissingSingleton) {
  33   EXPECT_DEATH([]() { auto u = Singleton<UnregisteredWatchdog>::try_get(); }(),
  34       "");
  35 }
  36
  37 struct BasicUsageTag {};
  38 template <typename T, typename Tag = detail::DefaultTag>
  39 using SingletonBasicUsage = Singleton <T, Tag, BasicUsageTag>;
  40
  41 // Exercise some basic codepaths ensuring registration order and
  42 // destruction order happen as expected, that instances are created
  43 // when expected, etc etc.
  44 TEST(Singleton, BasicUsage) {
  45   auto& vault = *SingletonVault::singleton<BasicUsageTag>();
  46
  47   EXPECT_EQ(vault.registeredSingletonCount(), 0);
  48   SingletonBasicUsage<Watchdog> watchdog_singleton;
  49   EXPECT_EQ(vault.registeredSingletonCount(), 1);
  50
  51   SingletonBasicUsage<ChildWatchdog> child_watchdog_singleton;
  52   EXPECT_EQ(vault.registeredSingletonCount(), 2);
  53
  54   vault.registrationComplete();
  55
  56   // limit a scope to release references so we can destroy them later
  57   {
  58     std::shared_ptr<Watchdog> s1 = SingletonBasicUsage<Watchdog>::try_get();
  59     EXPECT_NE(s1, nullptr);
  60
  61     std::shared_ptr<Watchdog> s2 = SingletonBasicUsage<Watchdog>::try_get();
  62     EXPECT_NE(s2, nullptr);
  63
  64     EXPECT_EQ(s1, s2);
  65     EXPECT_EQ(s1.get(), SingletonBasicUsage<Watchdog>::try_get_fast().get());
  66
  67     std::shared_ptr<ChildWatchdog> s3 =
  68       SingletonBasicUsage<ChildWatchdog>::try_get();
  69     EXPECT_NE(s3, nullptr);
  70     EXPECT_NE(s2, s3);
  71
  72     EXPECT_EQ(vault.registeredSingletonCount(), 2);
  73     EXPECT_EQ(vault.livingSingletonCount(), 2);
  74   }
  75
  76   vault.destroyInstances();
  77   EXPECT_EQ(vault.registeredSingletonCount(), 2);
  78   EXPECT_EQ(vault.livingSingletonCount(), 0);
  79 }
  80
  81 struct DirectUsageTag {};
  82 template <typename T, typename Tag = detail::DefaultTag>
  83 using SingletonDirectUsage = Singleton <T, Tag, DirectUsageTag>;
  84
  85 TEST(Singleton, DirectUsage) {
  86   auto& vault = *SingletonVault::singleton<DirectUsageTag>();
  87
  88   EXPECT_EQ(vault.registeredSingletonCount(), 0);
  89
  90   // Verify we can get to the underlying singletons via directly using
  91   // the singleton definition.
  92   SingletonDirectUsage<Watchdog> watchdog;
  93   struct TestTag {};
  94   SingletonDirectUsage<Watchdog, TestTag> named_watchdog;
  95   EXPECT_EQ(vault.registeredSingletonCount(), 2);
  96   vault.registrationComplete();
  97
  98   EXPECT_NE(watchdog.try_get(), nullptr);
  99   EXPECT_EQ(watchdog.try_get(), SingletonDirectUsage<Watchdog>::try_get());
 100   EXPECT_NE(watchdog.try_get(), named_watchdog.try_get());
 101   EXPECT_EQ(watchdog.try_get()->livingWatchdogCount(), 2);
 102
 103   vault.destroyInstances();
 104 }
 105
 106 struct NamedUsageTag {};
 107 template <typename T, typename Tag = detail::DefaultTag>
 108 using SingletonNamedUsage = Singleton <T, Tag, NamedUsageTag>;
 109
 110 TEST(Singleton, NamedUsage) {
 111   auto& vault = *SingletonVault::singleton<NamedUsageTag>();
 112
 113   EXPECT_EQ(vault.registeredSingletonCount(), 0);
 114
 115   // Define two named Watchdog singletons and one unnamed singleton.
 116   struct Watchdog1 {};
 117   struct Watchdog2 {};
 118   typedef detail::DefaultTag Watchdog3;
 119   SingletonNamedUsage<Watchdog, Watchdog1> watchdog1_singleton;
 120   EXPECT_EQ(vault.registeredSingletonCount(), 1);
 121   SingletonNamedUsage<Watchdog, Watchdog2> watchdog2_singleton;
 122   EXPECT_EQ(vault.registeredSingletonCount(), 2);
 123   SingletonNamedUsage<Watchdog, Watchdog3> watchdog3_singleton;
 124   EXPECT_EQ(vault.registeredSingletonCount(), 3);
 125
 126   vault.registrationComplete();
 127   {
 128     // Verify our three singletons are distinct and non-nullptr.
 129     auto s1 = SingletonNamedUsage<Watchdog, Watchdog1>::try_get();
 130     EXPECT_EQ(s1, watchdog1_singleton.try_get());
 131     auto s2 = SingletonNamedUsage<Watchdog, Watchdog2>::try_get();
 132     EXPECT_EQ(s2, watchdog2_singleton.try_get());
 133     EXPECT_NE(s1, s2);
 134     auto s3 = SingletonNamedUsage<Watchdog, Watchdog3>::try_get();
 135     EXPECT_EQ(s3, watchdog3_singleton.try_get());
 136     EXPECT_NE(s3, s1);
 137     EXPECT_NE(s3, s2);
 138
 139     // Verify the "default" singleton is the same as the DefaultTag-tagged
 140     // singleton.
 141     auto s4 = SingletonNamedUsage<Watchdog>::try_get();
 142     EXPECT_EQ(s4, watchdog3_singleton.try_get());
 143   }
 144
 145   vault.destroyInstances();
 146 }
 147
 148 struct NaughtyUsageTag {};
 149 template <typename T, typename Tag = detail::DefaultTag>
 150 using SingletonNaughtyUsage = Singleton <T, Tag, NaughtyUsageTag>;
 151 struct NaughtyUsageTag2 {};
 152 template <typename T, typename Tag = detail::DefaultTag>
 153 using SingletonNaughtyUsage2 = Singleton <T, Tag, NaughtyUsageTag2>;
 154
 155 // Some pathological cases such as getting unregistered singletons,
 156 // double registration, etc.
 157 TEST(Singleton, NaughtyUsage) {
 158   auto& vault = *SingletonVault::singleton<NaughtyUsageTag>();
 159
 160   vault.registrationComplete();
 161
 162   // Unregistered.
 163   EXPECT_DEATH(Singleton<Watchdog>::try_get(), "");
 164   EXPECT_DEATH(SingletonNaughtyUsage<Watchdog>::try_get(), "");
 165
 166   vault.destroyInstances();
 167
 168   auto& vault2 = *SingletonVault::singleton<NaughtyUsageTag2>();
 169
 170    EXPECT_DEATH(SingletonNaughtyUsage2<Watchdog>::try_get(), "");
 171   SingletonNaughtyUsage2<Watchdog> watchdog_singleton;
 172
 173   // double registration
 174   EXPECT_DEATH([]() { SingletonNaughtyUsage2<Watchdog> watchdog_singleton; }(),
 175                "");
 176   vault2.destroyInstances();
 177
 178   // double registration after destroy
 179   EXPECT_DEATH([]() { SingletonNaughtyUsage2<Watchdog> watchdog_singleton; }(),
 180                "");
 181 }
 182
 183 struct SharedPtrUsageTag {};
 184 template <typename T, typename Tag = detail::DefaultTag>
 185 using SingletonSharedPtrUsage = Singleton <T, Tag, SharedPtrUsageTag>;
 186
 187 // TODO (anob): revisit this test
 188 TEST(Singleton, SharedPtrUsage) {
 189   struct WatchdogHolder {
 190     ~WatchdogHolder() {
 191       if (watchdog) {
 192         LOG(ERROR) << "The following log message with stack trace is expected";
 193       }
 194     }
 195
 196     std::shared_ptr<Watchdog> watchdog;
 197   };
 198
 199   auto& vault = *SingletonVault::singleton<SharedPtrUsageTag>();
 200
 201   EXPECT_EQ(vault.registeredSingletonCount(), 0);
 202   SingletonSharedPtrUsage<Watchdog> watchdog_singleton;
 203   EXPECT_EQ(vault.registeredSingletonCount(), 1);
 204
 205   SingletonSharedPtrUsage<ChildWatchdog> child_watchdog_singleton;
 206   EXPECT_EQ(vault.registeredSingletonCount(), 2);
 207
 208   struct ATag {};
 209   SingletonSharedPtrUsage<Watchdog, ATag> named_watchdog_singleton;
 210
 211   SingletonSharedPtrUsage<WatchdogHolder> watchdog_holder_singleton;
 212
 213   vault.registrationComplete();
 214
 215   // Initilize holder singleton first, so that it's the last one to be
 216   // destroyed.
 217   watchdog_holder_singleton.try_get();
 218
 219   auto s1 = SingletonSharedPtrUsage<Watchdog>::try_get().get();
 220   EXPECT_NE(s1, nullptr);
 221
 222   auto s2 = SingletonSharedPtrUsage<Watchdog>::try_get().get();
 223   EXPECT_NE(s2, nullptr);
 224
 225   EXPECT_EQ(s1, s2);
 226
 227   auto weak_s1 = SingletonSharedPtrUsage<Watchdog>::get_weak();
 228
 229   auto shared_s1 = weak_s1.lock();
 230   EXPECT_EQ(shared_s1.get(), s1);
 231   EXPECT_EQ(shared_s1.use_count(), 2);
 232
 233   auto old_serial = shared_s1->serial_number;
 234
 235   {
 236     auto named_weak_s1 =
 237       SingletonSharedPtrUsage<Watchdog, ATag>::get_weak();
 238     auto locked = named_weak_s1.lock();
 239     EXPECT_NE(locked.get(), shared_s1.get());
 240   }
 241
 242   // We should release externally locked shared_ptr, otherwise it will be
 243   // considered a leak
 244   watchdog_holder_singleton.try_get()->watchdog = std::move(shared_s1);
 245
 246   LOG(ERROR) << "The following log message regarding shared_ptr is expected";
 247   {
 248     auto start_time = std::chrono::steady_clock::now();
 249     vault.destroyInstances();
 250     auto duration = std::chrono::steady_clock::now() - start_time;
 251     EXPECT_TRUE(duration > std::chrono::seconds{4} &&
 252                 duration < std::chrono::seconds{6});
 253   }
 254   EXPECT_EQ(vault.registeredSingletonCount(), 4);
 255   EXPECT_EQ(vault.livingSingletonCount(), 0);
 256
 257   EXPECT_TRUE(weak_s1.expired());
 258
 259   auto empty_s1 = SingletonSharedPtrUsage<Watchdog>::get_weak();
 260   EXPECT_FALSE(empty_s1.lock());
 261
 262   vault.reenableInstances();
 263
 264   {
 265     // Singleton should be re-created only after reenableInstances() was called.
 266     auto new_s1 = SingletonSharedPtrUsage<Watchdog>::try_get();
 267     // Track serial number rather than pointer since the memory could be
 268     // re-used when we create new_s1.
 269     EXPECT_NE(new_s1->serial_number, old_serial);
 270   }
 271
 272   auto new_s1_weak = SingletonSharedPtrUsage<Watchdog>::get_weak();
 273   auto new_s1_shared = new_s1_weak.lock();
 274   std::thread t([new_s1_shared]() mutable {
 275       std::this_thread::sleep_for(std::chrono::seconds{2});
 276       new_s1_shared.reset();
 277     });
 278   new_s1_shared.reset();
 279   {
 280     auto start_time = std::chrono::steady_clock::now();
 281     vault.destroyInstances();
 282     auto duration = std::chrono::steady_clock::now() - start_time;
 283     EXPECT_TRUE(duration > std::chrono::seconds{1} &&
 284                 duration < std::chrono::seconds{3});
 285   }
 286   EXPECT_TRUE(new_s1_weak.expired());
 287   t.join();
 288 }
 289
 290 // Some classes to test singleton dependencies.  NeedySingleton has a
 291 // dependency on NeededSingleton, which happens during its
 292 // construction.
 293 struct NeedyTag {};
 294 template <typename T, typename Tag = detail::DefaultTag>
 295 using SingletonNeedy = Singleton <T, Tag, NeedyTag>;
 296
 297 struct NeededSingleton {};
 298 struct NeedySingleton {
 299   NeedySingleton() {
 300     auto unused = SingletonNeedy<NeededSingleton>::try_get();
 301     EXPECT_NE(unused, nullptr);
 302   }
 303 };
 304
 305 // Ensure circular dependencies fail -- a singleton that needs itself, whoops.
 306 struct SelfNeedyTag {};
 307 template <typename T, typename Tag = detail::DefaultTag>
 308 using SingletonSelfNeedy = Singleton <T, Tag, SelfNeedyTag>;
 309
 310 struct SelfNeedySingleton {
 311   SelfNeedySingleton() {
 312     auto unused = SingletonSelfNeedy<SelfNeedySingleton>::try_get();
 313     EXPECT_NE(unused, nullptr);
 314   }
 315 };
 316
 317 TEST(Singleton, SingletonDependencies) {
 318   SingletonNeedy<NeededSingleton> needed_singleton;
 319   SingletonNeedy<NeedySingleton> needy_singleton;
 320   auto& needy_vault = *SingletonVault::singleton<NeedyTag>();
 321
 322   needy_vault.registrationComplete();
 323
 324   EXPECT_EQ(needy_vault.registeredSingletonCount(), 2);
 325   EXPECT_EQ(needy_vault.livingSingletonCount(), 0);
 326
 327   auto needy = SingletonNeedy<NeedySingleton>::try_get();
 328   EXPECT_EQ(needy_vault.livingSingletonCount(), 2);
 329
 330   SingletonSelfNeedy<SelfNeedySingleton> self_needy_singleton;
 331   auto& self_needy_vault = *SingletonVault::singleton<SelfNeedyTag>();
 332
 333   self_needy_vault.registrationComplete();
 334   EXPECT_DEATH([]() { SingletonSelfNeedy<SelfNeedySingleton>::try_get(); }(),
 335       "");
 336 }
 337
 338 // A test to ensure multiple threads contending on singleton creation
 339 // properly wait for creation rather than thinking it is a circular
 340 // dependency.
 341 class Slowpoke : public Watchdog {
 342  public:
 343   Slowpoke() { std::this_thread::sleep_for(std::chrono::milliseconds(10)); }
 344 };
 345
 346 struct ConcurrencyTag {};
 347 template <typename T, typename Tag = detail::DefaultTag>
 348 using SingletonConcurrency = Singleton <T, Tag, ConcurrencyTag>;
 349
 350 TEST(Singleton, SingletonConcurrency) {
 351   auto& vault = *SingletonVault::singleton<ConcurrencyTag>();
 352   SingletonConcurrency<Slowpoke> slowpoke_singleton;
 353   vault.registrationComplete();
 354
 355   std::mutex gatekeeper;
 356   gatekeeper.lock();
 357   auto func = [&gatekeeper]() {
 358     gatekeeper.lock();
 359     gatekeeper.unlock();
 360     auto unused = SingletonConcurrency<Slowpoke>::try_get();
 361   };
 362
 363   EXPECT_EQ(vault.livingSingletonCount(), 0);
 364   std::vector<std::thread> threads;
 365   for (int i = 0; i < 100; ++i) {
 366     threads.emplace_back(func);
 367   }
 368   // If circular dependency checks fail, the unlock would trigger a
 369   // crash.  Instead, it succeeds, and we have exactly one living
 370   // singleton.
 371   gatekeeper.unlock();
 372   for (auto& t : threads) {
 373     t.join();
 374   }
 375   EXPECT_EQ(vault.livingSingletonCount(), 1);
 376 }
 377
 378 struct ErrorConstructor {
 379   static size_t constructCount_;
 380   ErrorConstructor() {
 381     if ((constructCount_++) == 0) {
 382       throw std::runtime_error("first time fails");
 383     }
 384   }
 385 };
 386 size_t ErrorConstructor::constructCount_(0);
 387
 388 struct CreationErrorTag {};
 389 template <typename T, typename Tag = detail::DefaultTag>
 390 using SingletonCreationError = Singleton<T, Tag, CreationErrorTag>;
 391
 392 TEST(Singleton, SingletonCreationError) {
 393   SingletonVault::singleton<CreationErrorTag>();
 394   SingletonCreationError<ErrorConstructor> error_once_singleton;
 395
 396   // first time should error out
 397   EXPECT_THROW(error_once_singleton.try_get(), std::runtime_error);
 398
 399   // second time it'll work fine
 400   error_once_singleton.try_get();
 401   SUCCEED();
 402 }
 403
 404 struct ConcurrencyStressTag {};
 405 template <typename T, typename Tag = detail::DefaultTag>
 406 using SingletonConcurrencyStress = Singleton <T, Tag, ConcurrencyStressTag>;
 407
 408 TEST(Singleton, SingletonConcurrencyStress) {
 409   auto& vault = *SingletonVault::singleton<ConcurrencyStressTag>();
 410   SingletonConcurrencyStress<Slowpoke> slowpoke_singleton;
 411
 412   std::vector<std::thread> ts;
 413   for (size_t i = 0; i < 100; ++i) {
 414     ts.emplace_back([&]() {
 415         slowpoke_singleton.try_get();
 416       });
 417   }
 418
 419   for (size_t i = 0; i < 100; ++i) {
 420     std::chrono::milliseconds d(20);
 421
 422     std::this_thread::sleep_for(d);
 423     vault.destroyInstances();
 424     std::this_thread::sleep_for(d);
 425     vault.destroyInstances();
 426   }
 427
 428   for (auto& t : ts) {
 429     t.join();
 430   }
 431 }
 432
 433 namespace {
 434 struct EagerInitSyncTag {};
 435 }
 436 template <typename T, typename Tag = detail::DefaultTag>
 437 using SingletonEagerInitSync = Singleton<T, Tag, EagerInitSyncTag>;
 438 TEST(Singleton, SingletonEagerInitSync) {
 439   auto& vault = *SingletonVault::singleton<EagerInitSyncTag>();
 440   bool didEagerInit = false;
 441   auto sing = SingletonEagerInitSync<std::string>(
 442                   [&] {didEagerInit = true; return new std::string("foo"); })
 443               .shouldEagerInit();
 444   vault.registrationComplete();
 445   EXPECT_FALSE(didEagerInit);
 446   vault.doEagerInit();
 447   EXPECT_TRUE(didEagerInit);
 448   sing.get_weak();  // (avoid compile error complaining about unused var 'sing')
 449 }
 450
 451 namespace {
 452 struct EagerInitAsyncTag {};
 453 }
 454 template <typename T, typename Tag = detail::DefaultTag>
 455 using SingletonEagerInitAsync = Singleton<T, Tag, EagerInitAsyncTag>;
 456 TEST(Singleton, SingletonEagerInitAsync) {
 457   auto& vault = *SingletonVault::singleton<EagerInitAsyncTag>();
 458   bool didEagerInit = false;
 459   auto sing = SingletonEagerInitAsync<std::string>(
 460                   [&] {didEagerInit = true; return new std::string("foo"); })
 461               .shouldEagerInit();
 462   folly::EventBase eb;
 463   folly::Baton<> done;
 464   vault.registrationComplete();
 465   EXPECT_FALSE(didEagerInit);
 466   vault.doEagerInitVia(eb, &done);
 467   eb.loop();
 468   done.wait();
 469   EXPECT_TRUE(didEagerInit);
 470   sing.get_weak();  // (avoid compile error complaining about unused var 'sing')
 471 }
 472
 473 namespace {
 474 class TestEagerInitParallelExecutor : public folly::Executor {
 475  public:
 476   explicit TestEagerInitParallelExecutor(const size_t threadCount) {
 477     eventBases_.reserve(threadCount);
 478     threads_.reserve(threadCount);
 479     for (size_t i = 0; i < threadCount; i++) {
 480       eventBases_.push_back(std::make_shared<folly::EventBase>());
 481       auto eb = eventBases_.back();
 482       threads_.emplace_back(std::make_shared<std::thread>(
 483           [eb] { eb->loopForever(); }));
 484     }
 485   }
 486
 487   virtual ~TestEagerInitParallelExecutor() override {
 488     for (auto eb : eventBases_) {
 489       eb->runInEventBaseThread([eb] { eb->terminateLoopSoon(); });
 490     }
 491     for (auto thread : threads_) {
 492       thread->join();
 493     }
 494   }
 495
 496   virtual void add(folly::Func func) override {
 497     const auto index = (counter_ ++) % eventBases_.size();
 498     eventBases_[index]->add(std::move(func));
 499   }
 500
 501  private:
 502   std::vector<std::shared_ptr<folly::EventBase>> eventBases_;
 503   std::vector<std::shared_ptr<std::thread>> threads_;
 504   std::atomic<size_t> counter_ {0};
 505 };
 506 }  // namespace
 507
 508 namespace {
 509 struct EagerInitParallelTag {};
 510 }
 511 template <typename T, typename Tag = detail::DefaultTag>
 512 using SingletonEagerInitParallel = Singleton<T, Tag, EagerInitParallelTag>;
 513 TEST(Singleton, SingletonEagerInitParallel) {
 514   const static size_t kIters = 1000;
 515   const static size_t kThreads = 20;
 516
 517   std::atomic<size_t> initCounter;
 518
 519   auto& vault = *SingletonVault::singleton<EagerInitParallelTag>();
 520
 521   auto sing = SingletonEagerInitParallel<std::string>(
 522                   [&] {++initCounter; return new std::string(""); })
 523               .shouldEagerInit();
 524
 525   for (size_t i = 0; i < kIters; i++) {
 526     SCOPE_EXIT {
 527       // clean up each time
 528       vault.destroyInstances();
 529       vault.reenableInstances();
 530     };
 531
 532     initCounter.store(0);
 533
 534     {
 535       std::vector<std::shared_ptr<std::thread>> threads;
 536       boost::barrier barrier(kThreads);
 537       TestEagerInitParallelExecutor exe(kThreads);
 538       vault.registrationComplete();
 539
 540       EXPECT_EQ(0, initCounter.load());
 541
 542       for (size_t j = 0; j < kThreads; j++) {
 543         threads.push_back(std::make_shared<std::thread>([&] {
 544           barrier.wait();
 545           vault.doEagerInitVia(exe);
 546         }));
 547       }
 548
 549       for (auto thread : threads) {
 550         thread->join();
 551       }
 552     }
 553
 554     EXPECT_EQ(1, initCounter.load());
 555
 556     sing.get_weak();  // (avoid compile error complaining about unused var)
 557   }
 558 }
 559
 560 struct MockTag {};
 561 template <typename T, typename Tag = detail::DefaultTag>
 562 using SingletonMock = Singleton <T, Tag, MockTag>;
 563
 564 // Verify that existing Singleton's can be overridden
 565 // using the make_mock functionality.
 566 TEST(Singleton, MockTest) {
 567   auto& vault = *SingletonVault::singleton<MockTag>();
 568
 569   SingletonMock<Watchdog> watchdog_singleton;
 570   vault.registrationComplete();
 571
 572   // Registring singletons after registrationComplete called works
 573   // with make_mock (but not with Singleton ctor).
 574   EXPECT_EQ(vault.registeredSingletonCount(), 1);
 575   int serial_count_first = SingletonMock<Watchdog>::try_get()->serial_number;
 576
 577   // Override existing mock using make_mock.
 578   SingletonMock<Watchdog>::make_mock();
 579
 580   EXPECT_EQ(vault.registeredSingletonCount(), 1);
 581   int serial_count_mock = SingletonMock<Watchdog>::try_get()->serial_number;
 582
 583   // If serial_count value is the same, then singleton was not replaced.
 584   EXPECT_NE(serial_count_first, serial_count_mock);
 585
 586   // Override existing mock using make_mock one more time
 587   SingletonMock<Watchdog>::make_mock();
 588
 589   EXPECT_EQ(vault.registeredSingletonCount(), 1);
 590   int serial_count_mock2 = SingletonMock<Watchdog>::try_get()->serial_number;
 591
 592   // If serial_count value is the same, then singleton was not replaced.
 593   EXPECT_NE(serial_count_first, serial_count_mock2);
 594   EXPECT_NE(serial_count_mock, serial_count_mock2);
 595
 596   vault.destroyInstances();
 597 }
 598
 599 TEST(Singleton, DoubleRegistrationLogging) {
 600   const auto basename = "singleton_double_registration";
 601   const auto sub = fs::executable_path().remove_filename() / basename;
 602   auto p = Subprocess(
 603       std::vector<std::string>{sub.string()},
 604       Subprocess::Options()
 605           .stdin(Subprocess::CLOSE)
 606           .stdout(Subprocess::CLOSE)
 607           .pipeStderr()
 608           .closeOtherFds());
 609   auto err = p.communicate("").second;
 610   auto res = p.wait();
 611   EXPECT_EQ(ProcessReturnCode::KILLED, res.state());
 612   EXPECT_EQ(SIGABRT, res.killSignal());
 613   EXPECT_THAT(err, testing::StartsWith("Double registration of singletons"));
 614 }