/ src / test / coins_tests.cpp
coins_tests.cpp
   1  // Copyright (c) 2014-present The Bitcoin Core developers
   2  // Distributed under the MIT software license, see the accompanying
   3  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   4  
   5  #include <addresstype.h>
   6  #include <clientversion.h>
   7  #include <coins.h>
   8  #include <streams.h>
   9  #include <test/util/common.h>
  10  #include <test/util/poolresourcetester.h>
  11  #include <test/util/random.h>
  12  #include <test/util/setup_common.h>
  13  #include <txdb.h>
  14  #include <uint256.h>
  15  #include <undo.h>
  16  #include <util/byte_units.h>
  17  #include <util/strencodings.h>
  18  
  19  #include <map>
  20  #include <string>
  21  #include <variant>
  22  #include <vector>
  23  
  24  #include <boost/test/unit_test.hpp>
  25  
  26  using namespace util::hex_literals;
  27  
  28  int ApplyTxInUndo(Coin&& undo, CCoinsViewCache& view, const COutPoint& out);
  29  void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, CTxUndo &txundo, int nHeight);
  30  
  31  namespace
  32  {
  33  //! equality test
  34  bool operator==(const Coin &a, const Coin &b) {
  35      // Empty Coin objects are always equal.
  36      if (a.IsSpent() && b.IsSpent()) return true;
  37      return a.fCoinBase == b.fCoinBase &&
  38             a.nHeight == b.nHeight &&
  39             a.out == b.out;
  40  }
  41  
  42  class CCoinsViewTest : public CoinsViewEmpty
  43  {
  44      FastRandomContext& m_rng;
  45      uint256 hashBestBlock_;
  46      std::map<COutPoint, Coin> map_;
  47  
  48  public:
  49      explicit CCoinsViewTest(FastRandomContext& rng) : m_rng{rng} {}
  50  
  51      std::optional<Coin> GetCoin(const COutPoint& outpoint) const override
  52      {
  53          if (auto it{map_.find(outpoint)}; it != map_.end() && !it->second.IsSpent()) return it->second;
  54          return std::nullopt;
  55      }
  56  
  57      uint256 GetBestBlock() const override { return hashBestBlock_; }
  58  
  59      void BatchWrite(CoinsViewCacheCursor& cursor, const uint256& block_hash) override
  60      {
  61          for (auto it{cursor.Begin()}; it != cursor.End(); it = cursor.NextAndMaybeErase(*it)){
  62              if (it->second.IsDirty()) {
  63                  // Same optimization used in CCoinsViewDB is to only write dirty entries.
  64                  map_[it->first] = it->second.coin;
  65                  if (it->second.coin.IsSpent() && m_rng.randrange(3) == 0) {
  66                      // Randomly delete empty entries on write.
  67                      map_.erase(it->first);
  68                  }
  69              }
  70          }
  71          if (!block_hash.IsNull())
  72              hashBestBlock_ = block_hash;
  73      }
  74  };
  75  
  76  class CCoinsViewCacheTest : public CCoinsViewCache
  77  {
  78  public:
  79      explicit CCoinsViewCacheTest(CCoinsView* _base) : CCoinsViewCache(_base) {}
  80  
  81      void SelfTest(bool sanity_check = true) const
  82      {
  83          // Manually recompute the dynamic usage of the whole data, and compare it.
  84          size_t ret = memusage::DynamicUsage(cacheCoins);
  85          size_t count = 0;
  86          for (const auto& entry : cacheCoins) {
  87              ret += entry.second.coin.DynamicMemoryUsage();
  88              ++count;
  89          }
  90          BOOST_CHECK_EQUAL(GetCacheSize(), count);
  91          BOOST_CHECK_EQUAL(DynamicMemoryUsage(), ret);
  92          if (sanity_check) {
  93              SanityCheck();
  94          }
  95      }
  96  
  97      CCoinsMap& map() const { return cacheCoins; }
  98      CoinsCachePair& sentinel() const { return m_sentinel; }
  99      size_t& usage() const { return cachedCoinsUsage; }
 100      size_t& dirty() const { return m_dirty_count; }
 101  };
 102  
 103  } // namespace
 104  
 105  static const unsigned int NUM_SIMULATION_ITERATIONS = 40000;
 106  
 107  struct CacheTest : BasicTestingSetup {
 108  // This is a large randomized insert/remove simulation test on a variable-size
 109  // stack of caches on top of CCoinsViewTest.
 110  //
 111  // It will randomly create/update/delete Coin entries to a tip of caches, with
 112  // txids picked from a limited list of random 256-bit hashes. Occasionally, a
 113  // new tip is added to the stack of caches, or the tip is flushed and removed.
 114  //
 115  // During the process, booleans are kept to make sure that the randomized
 116  // operation hits all branches.
 117  //
 118  // If fake_best_block is true, assign a random uint256 to mock the recording
 119  // of best block on flush. This is necessary when using CCoinsViewDB as the base,
 120  // otherwise we'll hit an assertion in BatchWrite.
 121  //
 122  void SimulationTest(CCoinsView* base, bool fake_best_block)
 123  {
 124      // Various coverage trackers.
 125      bool removed_all_caches = false;
 126      bool reached_4_caches = false;
 127      bool added_an_entry = false;
 128      bool added_an_unspendable_entry = false;
 129      bool removed_an_entry = false;
 130      bool updated_an_entry = false;
 131      bool found_an_entry = false;
 132      bool missed_an_entry = false;
 133      bool uncached_an_entry = false;
 134      bool flushed_without_erase = false;
 135  
 136      // A simple map to track what we expect the cache stack to represent.
 137      std::map<COutPoint, Coin> result;
 138  
 139      // The cache stack.
 140      std::vector<std::unique_ptr<CCoinsViewCacheTest>> stack; // A stack of CCoinsViewCaches on top.
 141      stack.push_back(std::make_unique<CCoinsViewCacheTest>(base)); // Start with one cache.
 142  
 143      // Use a limited set of random transaction ids, so we do test overwriting entries.
 144      std::vector<Txid> txids;
 145      txids.resize(NUM_SIMULATION_ITERATIONS / 8);
 146      for (unsigned int i = 0; i < txids.size(); i++) {
 147          txids[i] = Txid::FromUint256(m_rng.rand256());
 148      }
 149  
 150      for (unsigned int i = 0; i < NUM_SIMULATION_ITERATIONS; i++) {
 151          // Do a random modification.
 152          {
 153              auto txid = txids[m_rng.randrange(txids.size())]; // txid we're going to modify in this iteration.
 154              Coin& coin = result[COutPoint(txid, 0)];
 155  
 156              // Determine whether to test HaveCoin before or after Access* (or both). As these functions
 157              // can influence each other's behaviour by pulling things into the cache, all combinations
 158              // are tested.
 159              bool test_havecoin_before = m_rng.randbits(2) == 0;
 160              bool test_havecoin_after = m_rng.randbits(2) == 0;
 161  
 162              bool result_havecoin = test_havecoin_before ? stack.back()->HaveCoin(COutPoint(txid, 0)) : false;
 163  
 164              // Infrequently, test usage of AccessByTxid instead of AccessCoin - the
 165              // former just delegates to the latter and returns the first unspent in a txn.
 166              const Coin& entry = (m_rng.randrange(500) == 0) ?
 167                  AccessByTxid(*stack.back(), txid) : stack.back()->AccessCoin(COutPoint(txid, 0));
 168              BOOST_CHECK(coin == entry);
 169  
 170              if (test_havecoin_before) {
 171                  BOOST_CHECK(result_havecoin == !entry.IsSpent());
 172              }
 173  
 174              if (test_havecoin_after) {
 175                  bool ret = stack.back()->HaveCoin(COutPoint(txid, 0));
 176                  BOOST_CHECK(ret == !entry.IsSpent());
 177              }
 178  
 179              if (m_rng.randrange(5) == 0 || coin.IsSpent()) {
 180                  Coin newcoin;
 181                  newcoin.out.nValue = RandMoney(m_rng);
 182                  newcoin.nHeight = 1;
 183  
 184                  // Infrequently test adding unspendable coins.
 185                  if (m_rng.randrange(16) == 0 && coin.IsSpent()) {
 186                      newcoin.out.scriptPubKey.assign(1 + m_rng.randbits(6), OP_RETURN);
 187                      BOOST_CHECK(newcoin.out.scriptPubKey.IsUnspendable());
 188                      added_an_unspendable_entry = true;
 189                  } else {
 190                      // Random sizes so we can test memory usage accounting
 191                      newcoin.out.scriptPubKey.assign(m_rng.randbits(6), 0);
 192                      (coin.IsSpent() ? added_an_entry : updated_an_entry) = true;
 193                      coin = newcoin;
 194                  }
 195                  if (COutPoint op(txid, 0); !stack.back()->map().contains(op) && !newcoin.out.scriptPubKey.IsUnspendable() && m_rng.randbool()) {
 196                      stack.back()->EmplaceCoinInternalDANGER(std::move(op), std::move(newcoin));
 197                  } else {
 198                      stack.back()->AddCoin(op, std::move(newcoin), /*possible_overwrite=*/!coin.IsSpent() || m_rng.randbool());
 199                  }
 200              } else {
 201                  // Spend the coin.
 202                  removed_an_entry = true;
 203                  coin.Clear();
 204                  BOOST_CHECK(stack.back()->SpendCoin(COutPoint(txid, 0)));
 205              }
 206          }
 207  
 208          // Once every 10 iterations, remove a random entry from the cache
 209          if (m_rng.randrange(10) == 0) {
 210              COutPoint out(txids[m_rng.rand32() % txids.size()], 0);
 211              int cacheid = m_rng.rand32() % stack.size();
 212              stack[cacheid]->Uncache(out);
 213              uncached_an_entry |= !stack[cacheid]->HaveCoinInCache(out);
 214          }
 215  
 216          // Once every 1000 iterations and at the end, verify the full cache.
 217          if (m_rng.randrange(1000) == 1 || i == NUM_SIMULATION_ITERATIONS - 1) {
 218              for (const auto& entry : result) {
 219                  bool have = stack.back()->HaveCoin(entry.first);
 220                  const Coin& coin = stack.back()->AccessCoin(entry.first);
 221                  BOOST_CHECK(have == !coin.IsSpent());
 222                  BOOST_CHECK(coin == entry.second);
 223                  if (coin.IsSpent()) {
 224                      missed_an_entry = true;
 225                  } else {
 226                      BOOST_CHECK(stack.back()->HaveCoinInCache(entry.first));
 227                      found_an_entry = true;
 228                  }
 229              }
 230              for (const auto& test : stack) {
 231                  test->SelfTest();
 232              }
 233          }
 234  
 235          if (m_rng.randrange(100) == 0) {
 236              // Every 100 iterations, flush an intermediate cache
 237              if (stack.size() > 1 && m_rng.randbool() == 0) {
 238                  unsigned int flushIndex = m_rng.randrange(stack.size() - 1);
 239                  if (fake_best_block) stack[flushIndex]->SetBestBlock(m_rng.rand256());
 240                  bool should_erase = m_rng.randrange(4) < 3;
 241                  should_erase ? stack[flushIndex]->Flush() : stack[flushIndex]->Sync();
 242                  flushed_without_erase |= !should_erase;
 243              }
 244          }
 245          if (m_rng.randrange(100) == 0) {
 246              // Every 100 iterations, change the cache stack.
 247              if (stack.size() > 0 && m_rng.randbool() == 0) {
 248                  //Remove the top cache
 249                  if (fake_best_block) stack.back()->SetBestBlock(m_rng.rand256());
 250                  bool should_erase = m_rng.randrange(4) < 3;
 251                  should_erase ? stack.back()->Flush() : stack.back()->Sync();
 252                  flushed_without_erase |= !should_erase;
 253                  stack.pop_back();
 254              }
 255              if (stack.size() == 0 || (stack.size() < 4 && m_rng.randbool())) {
 256                  //Add a new cache
 257                  CCoinsView* tip = base;
 258                  if (stack.size() > 0) {
 259                      tip = stack.back().get();
 260                  } else {
 261                      removed_all_caches = true;
 262                  }
 263                  stack.push_back(std::make_unique<CCoinsViewCacheTest>(tip));
 264                  if (stack.size() == 4) {
 265                      reached_4_caches = true;
 266                  }
 267              }
 268          }
 269      }
 270  
 271      // Verify coverage.
 272      BOOST_CHECK(removed_all_caches);
 273      BOOST_CHECK(reached_4_caches);
 274      BOOST_CHECK(added_an_entry);
 275      BOOST_CHECK(added_an_unspendable_entry);
 276      BOOST_CHECK(removed_an_entry);
 277      BOOST_CHECK(updated_an_entry);
 278      BOOST_CHECK(found_an_entry);
 279      BOOST_CHECK(missed_an_entry);
 280      BOOST_CHECK(uncached_an_entry);
 281      BOOST_CHECK(flushed_without_erase);
 282  }
 283  }; // struct CacheTest
 284  
 285  BOOST_FIXTURE_TEST_SUITE(coins_tests_base, BasicTestingSetup)
 286  
 287  // Run the above simulation for multiple base types.
 288  BOOST_FIXTURE_TEST_CASE(coins_cache_base_simulation_test, CacheTest)
 289  {
 290      CCoinsViewTest base{m_rng};
 291      SimulationTest(&base, false);
 292  }
 293  
 294  BOOST_AUTO_TEST_SUITE_END()
 295  
 296  BOOST_FIXTURE_TEST_SUITE(coins_tests_dbbase, BasicTestingSetup)
 297  
 298  BOOST_FIXTURE_TEST_CASE(coins_cache_dbbase_simulation_test, CacheTest)
 299  {
 300      CCoinsViewDB db_base{{.path = "test", .cache_bytes = 8_MiB, .memory_only = true}, {}};
 301      SimulationTest(&db_base, true);
 302  }
 303  
 304  BOOST_AUTO_TEST_SUITE_END()
 305  
 306  BOOST_FIXTURE_TEST_SUITE(coins_tests, BasicTestingSetup)
 307  
 308  struct UpdateTest : BasicTestingSetup {
 309  // Store of all necessary tx and undo data for next test
 310  typedef std::map<COutPoint, std::tuple<CTransaction,CTxUndo,Coin>> UtxoData;
 311  UtxoData utxoData;
 312  
 313  UtxoData::iterator FindRandomFrom(const std::set<COutPoint> &utxoSet) {
 314      assert(utxoSet.size());
 315      auto utxoSetIt = utxoSet.lower_bound(COutPoint(Txid::FromUint256(m_rng.rand256()), 0));
 316      if (utxoSetIt == utxoSet.end()) {
 317          utxoSetIt = utxoSet.begin();
 318      }
 319      auto utxoDataIt = utxoData.find(*utxoSetIt);
 320      assert(utxoDataIt != utxoData.end());
 321      return utxoDataIt;
 322  }
 323  }; // struct UpdateTest
 324  
 325  
 326  // This test is similar to the previous test
 327  // except the emphasis is on testing the functionality of UpdateCoins
 328  // random txs are created and UpdateCoins is used to update the cache stack
 329  // In particular it is tested that spending a duplicate coinbase tx
 330  // has the expected effect (the other duplicate is overwritten at all cache levels)
 331  BOOST_FIXTURE_TEST_CASE(updatecoins_simulation_test, UpdateTest)
 332  {
 333      SeedRandomForTest(SeedRand::ZEROS);
 334  
 335      bool spent_a_duplicate_coinbase = false;
 336      // A simple map to track what we expect the cache stack to represent.
 337      std::map<COutPoint, Coin> result;
 338  
 339      // The cache stack.
 340      CCoinsViewTest base{m_rng}; // A CCoinsViewTest at the bottom.
 341      std::vector<std::unique_ptr<CCoinsViewCacheTest>> stack; // A stack of CCoinsViewCaches on top.
 342      stack.push_back(std::make_unique<CCoinsViewCacheTest>(&base)); // Start with one cache.
 343  
 344      // Track the txids we've used in various sets
 345      std::set<COutPoint> coinbase_coins;
 346      std::set<COutPoint> disconnected_coins;
 347      std::set<COutPoint> duplicate_coins;
 348      std::set<COutPoint> utxoset;
 349  
 350      for (unsigned int i = 0; i < NUM_SIMULATION_ITERATIONS; i++) {
 351          uint32_t randiter = m_rng.rand32();
 352  
 353          // 19/20 txs add a new transaction
 354          if (randiter % 20 < 19) {
 355              CMutableTransaction tx;
 356              tx.vin.resize(1);
 357              tx.vout.resize(1);
 358              tx.vout[0].nValue = i; //Keep txs unique unless intended to duplicate
 359              tx.vout[0].scriptPubKey.assign(m_rng.rand32() & 0x3F, 0); // Random sizes so we can test memory usage accounting
 360              const int height{int(m_rng.rand32() >> 1)};
 361              Coin old_coin;
 362  
 363              // 2/20 times create a new coinbase
 364              if (randiter % 20 < 2 || coinbase_coins.size() < 10) {
 365                  // 1/10 of those times create a duplicate coinbase
 366                  if (m_rng.randrange(10) == 0 && coinbase_coins.size()) {
 367                      auto utxod = FindRandomFrom(coinbase_coins);
 368                      // Reuse the exact same coinbase
 369                      tx = CMutableTransaction{std::get<0>(utxod->second)};
 370                      // shouldn't be available for reconnection if it's been duplicated
 371                      disconnected_coins.erase(utxod->first);
 372  
 373                      duplicate_coins.insert(utxod->first);
 374                  }
 375                  else {
 376                      coinbase_coins.insert(COutPoint(tx.GetHash(), 0));
 377                  }
 378                  assert(CTransaction(tx).IsCoinBase());
 379              }
 380  
 381              // 17/20 times reconnect previous or add a regular tx
 382              else {
 383  
 384                  COutPoint prevout;
 385                  // 1/20 times reconnect a previously disconnected tx
 386                  if (randiter % 20 == 2 && disconnected_coins.size()) {
 387                      auto utxod = FindRandomFrom(disconnected_coins);
 388                      tx = CMutableTransaction{std::get<0>(utxod->second)};
 389                      prevout = tx.vin[0].prevout;
 390                      if (!CTransaction(tx).IsCoinBase() && !utxoset.contains(prevout)) {
 391                          disconnected_coins.erase(utxod->first);
 392                          continue;
 393                      }
 394  
 395                      // If this tx is already IN the UTXO, then it must be a coinbase, and it must be a duplicate
 396                      if (utxoset.contains(utxod->first)) {
 397                          assert(CTransaction(tx).IsCoinBase());
 398                          assert(duplicate_coins.contains(utxod->first));
 399                      }
 400                      disconnected_coins.erase(utxod->first);
 401                  }
 402  
 403                  // 16/20 times create a regular tx
 404                  else {
 405                      auto utxod = FindRandomFrom(utxoset);
 406                      prevout = utxod->first;
 407  
 408                      // Construct the tx to spend the coins of prevouthash
 409                      tx.vin[0].prevout = prevout;
 410                      assert(!CTransaction(tx).IsCoinBase());
 411                  }
 412                  // In this simple test coins only have two states, spent or unspent, save the unspent state to restore
 413                  old_coin = result[prevout];
 414                  // Update the expected result of prevouthash to know these coins are spent
 415                  result[prevout].Clear();
 416  
 417                  utxoset.erase(prevout);
 418  
 419                  // The test is designed to ensure spending a duplicate coinbase will work properly
 420                  // if that ever happens and not resurrect the previously overwritten coinbase
 421                  if (duplicate_coins.contains(prevout)) {
 422                      spent_a_duplicate_coinbase = true;
 423                  }
 424  
 425              }
 426              // Update the expected result to know about the new output coins
 427              assert(tx.vout.size() == 1);
 428              const COutPoint outpoint(tx.GetHash(), 0);
 429              result[outpoint] = Coin{tx.vout[0], height, CTransaction{tx}.IsCoinBase()};
 430  
 431              // Call UpdateCoins on the top cache
 432              CTxUndo undo;
 433              UpdateCoins(CTransaction{tx}, *(stack.back()), undo, height);
 434  
 435              // Update the utxo set for future spends
 436              utxoset.insert(outpoint);
 437  
 438              // Track this tx and undo info to use later
 439              utxoData.emplace(outpoint, std::make_tuple(tx,undo,old_coin));
 440          } else if (utxoset.size()) {
 441              //1/20 times undo a previous transaction
 442              auto utxod = FindRandomFrom(utxoset);
 443  
 444              CTransaction &tx = std::get<0>(utxod->second);
 445              CTxUndo &undo = std::get<1>(utxod->second);
 446              Coin &orig_coin = std::get<2>(utxod->second);
 447  
 448              // Update the expected result
 449              // Remove new outputs
 450              result[utxod->first].Clear();
 451              // If not coinbase restore prevout
 452              if (!tx.IsCoinBase()) {
 453                  result[tx.vin[0].prevout] = orig_coin;
 454              }
 455  
 456              // Disconnect the tx from the current UTXO
 457              // See code in DisconnectBlock
 458              // remove outputs
 459              BOOST_CHECK(stack.back()->SpendCoin(utxod->first));
 460              // restore inputs
 461              if (!tx.IsCoinBase()) {
 462                  const COutPoint &out = tx.vin[0].prevout;
 463                  Coin coin = undo.vprevout[0];
 464                  ApplyTxInUndo(std::move(coin), *(stack.back()), out);
 465              }
 466              // Store as a candidate for reconnection
 467              disconnected_coins.insert(utxod->first);
 468  
 469              // Update the utxoset
 470              utxoset.erase(utxod->first);
 471              if (!tx.IsCoinBase())
 472                  utxoset.insert(tx.vin[0].prevout);
 473          }
 474  
 475          // Once every 1000 iterations and at the end, verify the full cache.
 476          if (m_rng.randrange(1000) == 1 || i == NUM_SIMULATION_ITERATIONS - 1) {
 477              for (const auto& entry : result) {
 478                  bool have = stack.back()->HaveCoin(entry.first);
 479                  const Coin& coin = stack.back()->AccessCoin(entry.first);
 480                  BOOST_CHECK(have == !coin.IsSpent());
 481                  BOOST_CHECK(coin == entry.second);
 482              }
 483          }
 484  
 485          // One every 10 iterations, remove a random entry from the cache
 486          if (utxoset.size() > 1 && m_rng.randrange(30) == 0) {
 487              stack[m_rng.rand32() % stack.size()]->Uncache(FindRandomFrom(utxoset)->first);
 488          }
 489          if (disconnected_coins.size() > 1 && m_rng.randrange(30) == 0) {
 490              stack[m_rng.rand32() % stack.size()]->Uncache(FindRandomFrom(disconnected_coins)->first);
 491          }
 492          if (duplicate_coins.size() > 1 && m_rng.randrange(30) == 0) {
 493              stack[m_rng.rand32() % stack.size()]->Uncache(FindRandomFrom(duplicate_coins)->first);
 494          }
 495  
 496          if (m_rng.randrange(100) == 0) {
 497              // Every 100 iterations, flush an intermediate cache
 498              if (stack.size() > 1 && m_rng.randbool() == 0) {
 499                  unsigned int flushIndex = m_rng.randrange(stack.size() - 1);
 500                  stack[flushIndex]->Flush();
 501              }
 502          }
 503          if (m_rng.randrange(100) == 0) {
 504              // Every 100 iterations, change the cache stack.
 505              if (stack.size() > 0 && m_rng.randbool() == 0) {
 506                  stack.back()->Flush();
 507                  stack.pop_back();
 508              }
 509              if (stack.size() == 0 || (stack.size() < 4 && m_rng.randbool())) {
 510                  CCoinsView* tip = &base;
 511                  if (stack.size() > 0) {
 512                      tip = stack.back().get();
 513                  }
 514                  stack.push_back(std::make_unique<CCoinsViewCacheTest>(tip));
 515              }
 516          }
 517      }
 518  
 519      // Verify coverage.
 520      BOOST_CHECK(spent_a_duplicate_coinbase);
 521  }
 522  
 523  BOOST_AUTO_TEST_CASE(ccoins_serialization)
 524  {
 525      // Good example
 526      Coin cc1;
 527      SpanReader{"97f23c835800816115944e077fe7c803cfa57f29b36bf87c1d35"_hex} >> cc1;
 528      BOOST_CHECK_EQUAL(cc1.IsCoinBase(), false);
 529      BOOST_CHECK_EQUAL(cc1.nHeight, 203998U);
 530      BOOST_CHECK_EQUAL(cc1.out.nValue, CAmount{60000000000});
 531      BOOST_CHECK_EQUAL(HexStr(cc1.out.scriptPubKey), HexStr(GetScriptForDestination(PKHash(uint160("816115944e077fe7c803cfa57f29b36bf87c1d35"_hex_u8)))));
 532  
 533      // Good example
 534      Coin cc2;
 535      SpanReader{"8ddf77bbd123008c988f1a4a4de2161e0f50aac7f17e7f9555caa4"_hex} >> cc2;
 536      BOOST_CHECK_EQUAL(cc2.IsCoinBase(), true);
 537      BOOST_CHECK_EQUAL(cc2.nHeight, 120891U);
 538      BOOST_CHECK_EQUAL(cc2.out.nValue, 110397);
 539      BOOST_CHECK_EQUAL(HexStr(cc2.out.scriptPubKey), HexStr(GetScriptForDestination(PKHash(uint160("8c988f1a4a4de2161e0f50aac7f17e7f9555caa4"_hex_u8)))));
 540  
 541      // Smallest possible example
 542      Coin cc3;
 543      SpanReader{"000006"_hex} >> cc3;
 544      BOOST_CHECK_EQUAL(cc3.IsCoinBase(), false);
 545      BOOST_CHECK_EQUAL(cc3.nHeight, 0U);
 546      BOOST_CHECK_EQUAL(cc3.out.nValue, 0);
 547      BOOST_CHECK_EQUAL(cc3.out.scriptPubKey.size(), 0U);
 548  
 549      // scriptPubKey that ends beyond the end of the stream
 550      try {
 551          Coin cc4;
 552          SpanReader{"000007"_hex} >> cc4;
 553          BOOST_CHECK_MESSAGE(false, "We should have thrown");
 554      } catch (const std::ios_base::failure&) {
 555      }
 556  
 557      // Very large scriptPubKey (3*10^9 bytes) past the end of the stream
 558      DataStream tmp{};
 559      uint64_t x = 3000000000ULL;
 560      tmp << VARINT(x);
 561      BOOST_CHECK_EQUAL(HexStr(tmp), "8a95c0bb00");
 562      try {
 563          Coin cc5;
 564          SpanReader{"00008a95c0bb00"_hex} >> cc5;
 565          BOOST_CHECK_MESSAGE(false, "We should have thrown");
 566      } catch (const std::ios_base::failure&) {
 567      }
 568  }
 569  
 570  const static COutPoint OUTPOINT;
 571  constexpr CAmount SPENT {-1};
 572  constexpr CAmount ABSENT{-2};
 573  constexpr CAmount VALUE1{100};
 574  constexpr CAmount VALUE2{200};
 575  constexpr CAmount VALUE3{300};
 576  
 577  struct CoinEntry {
 578      enum class State { CLEAN, DIRTY, FRESH, DIRTY_FRESH };
 579  
 580      const CAmount value;
 581      const State state;
 582  
 583      constexpr CoinEntry(const CAmount v, const State s) : value{v}, state{s} {}
 584  
 585      bool operator==(const CoinEntry& o) const = default;
 586      friend std::ostream& operator<<(std::ostream& os, const CoinEntry& e) { return os << e.value << ", " << e.state; }
 587  
 588      constexpr bool IsDirtyFresh() const { return state == State::DIRTY_FRESH; }
 589      constexpr bool IsDirty() const { return state == State::DIRTY || IsDirtyFresh(); }
 590      constexpr bool IsFresh() const { return state == State::FRESH || IsDirtyFresh(); }
 591  
 592      static constexpr State ToState(const bool is_dirty, const bool is_fresh) {
 593          if (is_dirty && is_fresh) return State::DIRTY_FRESH;
 594          if (is_dirty) return State::DIRTY;
 595          if (is_fresh) return State::FRESH;
 596          return State::CLEAN;
 597      }
 598  };
 599  
 600  using MaybeCoin   = std::optional<CoinEntry>;
 601  using CoinOrError = std::variant<MaybeCoin, std::string>;
 602  
 603  constexpr MaybeCoin MISSING           {std::nullopt};
 604  constexpr MaybeCoin SPENT_DIRTY       {{SPENT,  CoinEntry::State::DIRTY}};
 605  constexpr MaybeCoin SPENT_DIRTY_FRESH {{SPENT,  CoinEntry::State::DIRTY_FRESH}};
 606  constexpr MaybeCoin SPENT_FRESH       {{SPENT,  CoinEntry::State::FRESH}};
 607  constexpr MaybeCoin SPENT_CLEAN       {{SPENT,  CoinEntry::State::CLEAN}};
 608  constexpr MaybeCoin VALUE1_DIRTY      {{VALUE1, CoinEntry::State::DIRTY}};
 609  constexpr MaybeCoin VALUE1_DIRTY_FRESH{{VALUE1, CoinEntry::State::DIRTY_FRESH}};
 610  constexpr MaybeCoin VALUE1_FRESH      {{VALUE1, CoinEntry::State::FRESH}};
 611  constexpr MaybeCoin VALUE1_CLEAN      {{VALUE1, CoinEntry::State::CLEAN}};
 612  constexpr MaybeCoin VALUE2_DIRTY      {{VALUE2, CoinEntry::State::DIRTY}};
 613  constexpr MaybeCoin VALUE2_DIRTY_FRESH{{VALUE2, CoinEntry::State::DIRTY_FRESH}};
 614  constexpr MaybeCoin VALUE2_FRESH      {{VALUE2, CoinEntry::State::FRESH}};
 615  constexpr MaybeCoin VALUE2_CLEAN      {{VALUE2, CoinEntry::State::CLEAN}};
 616  constexpr MaybeCoin VALUE3_DIRTY      {{VALUE3, CoinEntry::State::DIRTY}};
 617  constexpr MaybeCoin VALUE3_DIRTY_FRESH{{VALUE3, CoinEntry::State::DIRTY_FRESH}};
 618  
 619  constexpr auto EX_OVERWRITE_UNSPENT{"Attempted to overwrite an unspent coin (when possible_overwrite is false)"};
 620  constexpr auto EX_FRESH_MISAPPLIED {"FRESH flag misapplied to coin that exists in parent cache"};
 621  
 622  static void SetCoinsValue(const CAmount value, Coin& coin)
 623  {
 624      assert(value != ABSENT);
 625      coin.Clear();
 626      assert(coin.IsSpent());
 627      if (value != SPENT) {
 628          coin.out.nValue = value;
 629          coin.nHeight = 1;
 630          assert(!coin.IsSpent());
 631      }
 632  }
 633  
 634  static size_t InsertCoinsMapEntry(CCoinsMap& map, CoinsCachePair& sentinel, const CoinEntry& cache_coin)
 635  {
 636      CCoinsCacheEntry entry;
 637      SetCoinsValue(cache_coin.value, entry.coin);
 638      auto [iter, inserted] = map.emplace(OUTPOINT, std::move(entry));
 639      assert(inserted);
 640      if (cache_coin.IsDirty()) CCoinsCacheEntry::SetDirty(*iter, sentinel);
 641      if (cache_coin.IsFresh()) CCoinsCacheEntry::SetFresh(*iter, sentinel);
 642      return iter->second.coin.DynamicMemoryUsage();
 643  }
 644  
 645  static MaybeCoin GetCoinsMapEntry(const CCoinsMap& map, const COutPoint& outp = OUTPOINT)
 646  {
 647      if (auto it{map.find(outp)}; it != map.end()) {
 648          return CoinEntry{
 649              it->second.coin.IsSpent() ? SPENT : it->second.coin.out.nValue,
 650              CoinEntry::ToState(it->second.IsDirty(), it->second.IsFresh())};
 651      }
 652      return MISSING;
 653  }
 654  
 655  static void WriteCoinsViewEntry(CCoinsView& view, const MaybeCoin& cache_coin)
 656  {
 657      CoinsCachePair sentinel{};
 658      sentinel.second.SelfRef(sentinel);
 659      CCoinsMapMemoryResource resource;
 660      CCoinsMap map{0, CCoinsMap::hasher{}, CCoinsMap::key_equal{}, &resource};
 661      if (cache_coin) InsertCoinsMapEntry(map, sentinel, *cache_coin);
 662      size_t dirty_count{cache_coin && cache_coin->IsDirty()};
 663      auto cursor{CoinsViewCacheCursor(dirty_count, sentinel, map, /*will_erase=*/true)};
 664      view.BatchWrite(cursor, {});
 665      BOOST_CHECK_EQUAL(dirty_count, 0U);
 666  }
 667  
 668  class SingleEntryCacheTest
 669  {
 670  public:
 671      SingleEntryCacheTest(const CAmount base_value, const MaybeCoin& cache_coin)
 672      {
 673          auto base_cache_coin{base_value == ABSENT ? MISSING : CoinEntry{base_value, CoinEntry::State::DIRTY}};
 674          WriteCoinsViewEntry(base, base_cache_coin);
 675          if (cache_coin) {
 676              cache.usage() += InsertCoinsMapEntry(cache.map(), cache.sentinel(), *cache_coin);
 677              cache.dirty() += cache_coin->IsDirty();
 678          }
 679      }
 680  
 681      CCoinsViewCacheTest base{&CoinsViewEmpty::Get()};
 682      CCoinsViewCacheTest cache{&base};
 683  };
 684  
 685  static void CheckAccessCoin(const CAmount base_value, const MaybeCoin& cache_coin, const MaybeCoin& expected)
 686  {
 687      SingleEntryCacheTest test{base_value, cache_coin};
 688      auto& coin = test.cache.AccessCoin(OUTPOINT);
 689      BOOST_CHECK_EQUAL(coin.IsSpent(), !test.cache.GetCoin(OUTPOINT));
 690      test.cache.SelfTest(/*sanity_check=*/false);
 691      BOOST_CHECK_EQUAL(GetCoinsMapEntry(test.cache.map()), expected);
 692  }
 693  
 694  BOOST_AUTO_TEST_CASE(ccoins_access)
 695  {
 696      /* Check AccessCoin behavior, requesting a coin from a cache view layered on
 697       * top of a base view, and checking the resulting entry in the cache after
 698       * the access.
 699       *                  Base        Cache               Expected
 700       */
 701      for (auto base_value : {ABSENT, SPENT, VALUE1}) {
 702          CheckAccessCoin(base_value, MISSING,            base_value == VALUE1 ? VALUE1_CLEAN : MISSING);
 703  
 704          CheckAccessCoin(base_value, SPENT_CLEAN,        SPENT_CLEAN       );
 705          CheckAccessCoin(base_value, SPENT_FRESH,        SPENT_FRESH       );
 706          CheckAccessCoin(base_value, SPENT_DIRTY,        SPENT_DIRTY       );
 707          CheckAccessCoin(base_value, SPENT_DIRTY_FRESH,  SPENT_DIRTY_FRESH );
 708  
 709          CheckAccessCoin(base_value, VALUE2_CLEAN,       VALUE2_CLEAN      );
 710          CheckAccessCoin(base_value, VALUE2_FRESH,       VALUE2_FRESH      );
 711          CheckAccessCoin(base_value, VALUE2_DIRTY,       VALUE2_DIRTY      );
 712          CheckAccessCoin(base_value, VALUE2_DIRTY_FRESH, VALUE2_DIRTY_FRESH);
 713      }
 714  }
 715  
 716  static void CheckSpendCoins(const CAmount base_value, const MaybeCoin& cache_coin, const MaybeCoin& expected)
 717  {
 718      SingleEntryCacheTest test{base_value, cache_coin};
 719      test.cache.SpendCoin(OUTPOINT);
 720      test.cache.SelfTest();
 721      BOOST_CHECK_EQUAL(GetCoinsMapEntry(test.cache.map()), expected);
 722  }
 723  
 724  BOOST_AUTO_TEST_CASE(ccoins_spend)
 725  {
 726      /* Check SpendCoin behavior, requesting a coin from a cache view layered on
 727       * top of a base view, spending, and then checking
 728       * the resulting entry in the cache after the modification.
 729       *                  Base        Cache               Expected
 730       */
 731      for (auto base_value : {ABSENT, SPENT, VALUE1}) {
 732          CheckSpendCoins(base_value, MISSING,            base_value == VALUE1 ? SPENT_DIRTY : MISSING);
 733  
 734          CheckSpendCoins(base_value, SPENT_CLEAN,        SPENT_DIRTY);
 735          CheckSpendCoins(base_value, SPENT_FRESH,        MISSING    );
 736          CheckSpendCoins(base_value, SPENT_DIRTY,        SPENT_DIRTY);
 737          CheckSpendCoins(base_value, SPENT_DIRTY_FRESH,  MISSING    );
 738  
 739          CheckSpendCoins(base_value, VALUE2_CLEAN,       SPENT_DIRTY);
 740          CheckSpendCoins(base_value, VALUE2_FRESH,       MISSING    );
 741          CheckSpendCoins(base_value, VALUE2_DIRTY,       SPENT_DIRTY);
 742          CheckSpendCoins(base_value, VALUE2_DIRTY_FRESH, MISSING    );
 743      }
 744  }
 745  
 746  static void CheckAddCoin(const CAmount base_value, const MaybeCoin& cache_coin, const CAmount modify_value, const CoinOrError& expected, const bool coinbase)
 747  {
 748      SingleEntryCacheTest test{base_value, cache_coin};
 749      bool possible_overwrite{coinbase};
 750      auto add_coin{[&] { test.cache.AddCoin(OUTPOINT, Coin{CTxOut{modify_value, CScript{}}, 1, coinbase}, possible_overwrite); }};
 751      if (auto* expected_coin{std::get_if<MaybeCoin>(&expected)}) {
 752          add_coin();
 753          test.cache.SelfTest();
 754          BOOST_CHECK_EQUAL(GetCoinsMapEntry(test.cache.map()), *expected_coin);
 755      } else {
 756          BOOST_CHECK_EXCEPTION(add_coin(), std::logic_error, HasReason(std::get<std::string>(expected)));
 757      }
 758  }
 759  
 760  BOOST_AUTO_TEST_CASE(ccoins_add)
 761  {
 762      /* Check AddCoin behavior, requesting a new coin from a cache view,
 763       * writing a modification to the coin, and then checking the resulting
 764       * entry in the cache after the modification. Verify behavior with the
 765       * AddCoin coinbase argument set to false, and to true.
 766       *               Base        Cache               Write   Expected              Coinbase
 767       */
 768      for (auto base_value : {ABSENT, SPENT, VALUE1}) {
 769          CheckAddCoin(base_value, MISSING,            VALUE3, VALUE3_DIRTY_FRESH,   false);
 770          CheckAddCoin(base_value, MISSING,            VALUE3, VALUE3_DIRTY,         true );
 771  
 772          CheckAddCoin(base_value, SPENT_CLEAN,        VALUE3, VALUE3_DIRTY_FRESH,   false);
 773          CheckAddCoin(base_value, SPENT_CLEAN,        VALUE3, VALUE3_DIRTY,         true );
 774          CheckAddCoin(base_value, SPENT_FRESH,        VALUE3, VALUE3_DIRTY_FRESH,   false);
 775          CheckAddCoin(base_value, SPENT_FRESH,        VALUE3, VALUE3_DIRTY_FRESH,   true );
 776          CheckAddCoin(base_value, SPENT_DIRTY,        VALUE3, VALUE3_DIRTY,         false);
 777          CheckAddCoin(base_value, SPENT_DIRTY,        VALUE3, VALUE3_DIRTY,         true );
 778          CheckAddCoin(base_value, SPENT_DIRTY_FRESH,  VALUE3, VALUE3_DIRTY_FRESH,   false);
 779          CheckAddCoin(base_value, SPENT_DIRTY_FRESH,  VALUE3, VALUE3_DIRTY_FRESH,   true );
 780  
 781          CheckAddCoin(base_value, VALUE2_CLEAN,       VALUE3, EX_OVERWRITE_UNSPENT, false);
 782          CheckAddCoin(base_value, VALUE2_CLEAN,       VALUE3, VALUE3_DIRTY,         true );
 783          CheckAddCoin(base_value, VALUE2_FRESH,       VALUE3, EX_OVERWRITE_UNSPENT, false);
 784          CheckAddCoin(base_value, VALUE2_FRESH,       VALUE3, VALUE3_DIRTY_FRESH,   true );
 785          CheckAddCoin(base_value, VALUE2_DIRTY,       VALUE3, EX_OVERWRITE_UNSPENT, false);
 786          CheckAddCoin(base_value, VALUE2_DIRTY,       VALUE3, VALUE3_DIRTY,         true );
 787          CheckAddCoin(base_value, VALUE2_DIRTY_FRESH, VALUE3, EX_OVERWRITE_UNSPENT, false);
 788          CheckAddCoin(base_value, VALUE2_DIRTY_FRESH, VALUE3, VALUE3_DIRTY_FRESH,   true );
 789      }
 790  }
 791  
 792  static void CheckWriteCoins(const MaybeCoin& parent, const MaybeCoin& child, const CoinOrError& expected)
 793  {
 794      SingleEntryCacheTest test{ABSENT, parent};
 795      auto write_coins{[&] { WriteCoinsViewEntry(test.cache, child); }};
 796      if (auto* expected_coin{std::get_if<MaybeCoin>(&expected)}) {
 797          write_coins();
 798          test.cache.SelfTest(/*sanity_check=*/false);
 799          BOOST_CHECK_EQUAL(GetCoinsMapEntry(test.cache.map()), *expected_coin);
 800      } else {
 801          BOOST_CHECK_EXCEPTION(write_coins(), std::logic_error, HasReason(std::get<std::string>(expected)));
 802      }
 803  }
 804  
 805  BOOST_AUTO_TEST_CASE(ccoins_write)
 806  {
 807      /* Check BatchWrite behavior, flushing one entry from a child cache to a
 808       * parent cache, and checking the resulting entry in the parent cache
 809       * after the write.
 810       *              Parent              Child               Expected
 811       */
 812      CheckWriteCoins(MISSING,            MISSING,            MISSING            );
 813      CheckWriteCoins(MISSING,            SPENT_DIRTY,        SPENT_DIRTY        );
 814      CheckWriteCoins(MISSING,            SPENT_DIRTY_FRESH,  MISSING            );
 815      CheckWriteCoins(MISSING,            VALUE2_DIRTY,       VALUE2_DIRTY       );
 816      CheckWriteCoins(MISSING,            VALUE2_DIRTY_FRESH, VALUE2_DIRTY_FRESH );
 817      CheckWriteCoins(SPENT_CLEAN,        MISSING,            SPENT_CLEAN        );
 818      CheckWriteCoins(SPENT_FRESH,        MISSING,            SPENT_FRESH        );
 819      CheckWriteCoins(SPENT_DIRTY,        MISSING,            SPENT_DIRTY        );
 820      CheckWriteCoins(SPENT_DIRTY_FRESH,  MISSING,            SPENT_DIRTY_FRESH  );
 821  
 822      CheckWriteCoins(SPENT_CLEAN,        SPENT_DIRTY,        SPENT_DIRTY        );
 823      CheckWriteCoins(SPENT_CLEAN,        SPENT_DIRTY_FRESH,  SPENT_DIRTY        );
 824      CheckWriteCoins(SPENT_FRESH,        SPENT_DIRTY,        MISSING            );
 825      CheckWriteCoins(SPENT_FRESH,        SPENT_DIRTY_FRESH,  MISSING            );
 826      CheckWriteCoins(SPENT_DIRTY,        SPENT_DIRTY,        SPENT_DIRTY        );
 827      CheckWriteCoins(SPENT_DIRTY,        SPENT_DIRTY_FRESH,  SPENT_DIRTY        );
 828      CheckWriteCoins(SPENT_DIRTY_FRESH,  SPENT_DIRTY,        MISSING            );
 829      CheckWriteCoins(SPENT_DIRTY_FRESH,  SPENT_DIRTY_FRESH,  MISSING            );
 830  
 831      CheckWriteCoins(SPENT_CLEAN,        VALUE2_DIRTY,       VALUE2_DIRTY       );
 832      CheckWriteCoins(SPENT_CLEAN,        VALUE2_DIRTY_FRESH, VALUE2_DIRTY       );
 833      CheckWriteCoins(SPENT_FRESH,        VALUE2_DIRTY,       VALUE2_DIRTY_FRESH );
 834      CheckWriteCoins(SPENT_FRESH,        VALUE2_DIRTY_FRESH, VALUE2_DIRTY_FRESH );
 835      CheckWriteCoins(SPENT_DIRTY,        VALUE2_DIRTY,       VALUE2_DIRTY       );
 836      CheckWriteCoins(SPENT_DIRTY,        VALUE2_DIRTY_FRESH, VALUE2_DIRTY       );
 837      CheckWriteCoins(SPENT_DIRTY_FRESH,  VALUE2_DIRTY,       VALUE2_DIRTY_FRESH );
 838      CheckWriteCoins(SPENT_DIRTY_FRESH,  VALUE2_DIRTY_FRESH, VALUE2_DIRTY_FRESH );
 839  
 840      CheckWriteCoins(VALUE1_CLEAN,       MISSING,            VALUE1_CLEAN       );
 841      CheckWriteCoins(VALUE1_FRESH,       MISSING,            VALUE1_FRESH       );
 842      CheckWriteCoins(VALUE1_DIRTY,       MISSING,            VALUE1_DIRTY       );
 843      CheckWriteCoins(VALUE1_DIRTY_FRESH, MISSING,            VALUE1_DIRTY_FRESH );
 844      CheckWriteCoins(VALUE1_CLEAN,       SPENT_DIRTY,        SPENT_DIRTY        );
 845      CheckWriteCoins(VALUE1_CLEAN,       SPENT_DIRTY_FRESH,  EX_FRESH_MISAPPLIED);
 846      CheckWriteCoins(VALUE1_FRESH,       SPENT_DIRTY,        MISSING            );
 847      CheckWriteCoins(VALUE1_FRESH,       SPENT_DIRTY_FRESH,  EX_FRESH_MISAPPLIED);
 848      CheckWriteCoins(VALUE1_DIRTY,       SPENT_DIRTY,        SPENT_DIRTY        );
 849      CheckWriteCoins(VALUE1_DIRTY,       SPENT_DIRTY_FRESH,  EX_FRESH_MISAPPLIED);
 850      CheckWriteCoins(VALUE1_DIRTY_FRESH, SPENT_DIRTY,        MISSING            );
 851      CheckWriteCoins(VALUE1_DIRTY_FRESH, SPENT_DIRTY_FRESH,  EX_FRESH_MISAPPLIED);
 852  
 853      CheckWriteCoins(VALUE1_CLEAN,       VALUE2_DIRTY,       VALUE2_DIRTY       );
 854      CheckWriteCoins(VALUE1_CLEAN,       VALUE2_DIRTY_FRESH, EX_FRESH_MISAPPLIED);
 855      CheckWriteCoins(VALUE1_FRESH,       VALUE2_DIRTY,       VALUE2_DIRTY_FRESH );
 856      CheckWriteCoins(VALUE1_FRESH,       VALUE2_DIRTY_FRESH, EX_FRESH_MISAPPLIED);
 857      CheckWriteCoins(VALUE1_DIRTY,       VALUE2_DIRTY,       VALUE2_DIRTY       );
 858      CheckWriteCoins(VALUE1_DIRTY,       VALUE2_DIRTY_FRESH, EX_FRESH_MISAPPLIED);
 859      CheckWriteCoins(VALUE1_DIRTY_FRESH, VALUE2_DIRTY,       VALUE2_DIRTY_FRESH );
 860      CheckWriteCoins(VALUE1_DIRTY_FRESH, VALUE2_DIRTY_FRESH, EX_FRESH_MISAPPLIED);
 861  
 862      // The checks above omit cases where the child state is not DIRTY, since
 863      // they would be too repetitive (the parent cache is never updated in these
 864      // cases). The loop below covers these cases and makes sure the parent cache
 865      // is always left unchanged.
 866      for (const MaybeCoin& parent : {MISSING,
 867                                      SPENT_CLEAN, SPENT_DIRTY, SPENT_FRESH, SPENT_DIRTY_FRESH,
 868                                      VALUE1_CLEAN, VALUE1_DIRTY, VALUE1_FRESH, VALUE1_DIRTY_FRESH}) {
 869          for (const MaybeCoin& child : {MISSING,
 870                                         SPENT_CLEAN, SPENT_FRESH,
 871                                         VALUE2_CLEAN, VALUE2_FRESH}) {
 872              auto expected{CoinOrError{parent}}; // TODO test failure cases as well
 873              CheckWriteCoins(parent, child, expected);
 874          }
 875      }
 876  }
 877  
 878  struct FlushTest : BasicTestingSetup {
 879  Coin MakeCoin()
 880  {
 881      Coin coin;
 882      coin.out.nValue = m_rng.rand32();
 883      coin.nHeight = m_rng.randrange(4096);
 884      coin.fCoinBase = false;
 885      return coin;
 886  }
 887  
 888  
 889  //! For CCoinsViewCache instances backed by either another cache instance or
 890  //! leveldb, test cache behavior and flag state (DIRTY/FRESH) by
 891  //!
 892  //! 1. Adding a random coin to the child-most cache,
 893  //! 2. Flushing all caches (without erasing),
 894  //! 3. Ensure the entry still exists in the cache and has been written to parent,
 895  //! 4. (if `do_erasing_flush`) Flushing the caches again (with erasing),
 896  //! 5. (if `do_erasing_flush`) Ensure the entry has been written to the parent and is no longer in the cache,
 897  //! 6. Spend the coin, ensure it no longer exists in the parent.
 898  //!
 899  void TestFlushBehavior(
 900      CCoinsViewCacheTest* view,
 901      CCoinsViewDB& base,
 902      std::vector<std::unique_ptr<CCoinsViewCacheTest>>& all_caches,
 903      bool do_erasing_flush)
 904  {
 905      size_t cache_usage;
 906      size_t cache_size;
 907  
 908      auto flush_all = [this, &all_caches](bool erase) {
 909          // Flush in reverse order to ensure that flushes happen from children up.
 910          for (auto i = all_caches.rbegin(); i != all_caches.rend(); ++i) {
 911              auto& cache = *i;
 912              cache->SanityCheck();
 913              // block_hash must be filled before flushing to disk; value is
 914              // unimportant here. This is normally done during connect/disconnect block.
 915              cache->SetBestBlock(m_rng.rand256());
 916              erase ? cache->Flush() : cache->Sync();
 917          }
 918      };
 919  
 920      Txid txid = Txid::FromUint256(m_rng.rand256());
 921      COutPoint outp = COutPoint(txid, 0);
 922      Coin coin = MakeCoin();
 923      // Ensure the coins views haven't seen this coin before.
 924      BOOST_CHECK(!base.HaveCoin(outp));
 925      BOOST_CHECK(!view->HaveCoin(outp));
 926  
 927      // --- 1. Adding a random coin to the child cache
 928      //
 929      view->AddCoin(outp, Coin(coin), false);
 930  
 931      cache_usage = view->DynamicMemoryUsage();
 932      cache_size = view->map().size();
 933  
 934      // `base` shouldn't have coin (no flush yet) but `view` should have cached it.
 935      BOOST_CHECK(!base.HaveCoin(outp));
 936      BOOST_CHECK(view->HaveCoin(outp));
 937  
 938      BOOST_CHECK_EQUAL(GetCoinsMapEntry(view->map(), outp), CoinEntry(coin.out.nValue, CoinEntry::State::DIRTY_FRESH));
 939  
 940      // --- 2. Flushing all caches (without erasing)
 941      //
 942      flush_all(/*erase=*/ false);
 943  
 944      // CoinsMap usage should be unchanged since we didn't erase anything.
 945      BOOST_CHECK_EQUAL(cache_usage, view->DynamicMemoryUsage());
 946      BOOST_CHECK_EQUAL(cache_size, view->map().size());
 947  
 948      // --- 3. Ensuring the entry still exists in the cache and has been written to parent
 949      //
 950      BOOST_CHECK_EQUAL(GetCoinsMapEntry(view->map(), outp), CoinEntry(coin.out.nValue, CoinEntry::State::CLEAN)); // State should have been wiped.
 951  
 952      // Both views should now have the coin.
 953      BOOST_CHECK(base.HaveCoin(outp));
 954      BOOST_CHECK(view->HaveCoin(outp));
 955  
 956      if (do_erasing_flush) {
 957          // --- 4. Flushing the caches again (with erasing)
 958          //
 959          flush_all(/*erase=*/ true);
 960  
 961          // Memory does not necessarily go down due to the map using a memory pool
 962          BOOST_TEST(view->DynamicMemoryUsage() <= cache_usage);
 963          // Size of the cache must go down though
 964          BOOST_TEST(view->map().size() < cache_size);
 965  
 966          // --- 5. Ensuring the entry is no longer in the cache
 967          //
 968          BOOST_CHECK(!GetCoinsMapEntry(view->map(), outp));
 969          view->AccessCoin(outp);
 970          BOOST_CHECK_EQUAL(GetCoinsMapEntry(view->map(), outp), CoinEntry(coin.out.nValue, CoinEntry::State::CLEAN));
 971      }
 972  
 973      // Can't overwrite an entry without specifying that an overwrite is
 974      // expected.
 975      BOOST_CHECK_THROW(
 976          view->AddCoin(outp, Coin(coin), /*possible_overwrite=*/ false),
 977          std::logic_error);
 978  
 979      // --- 6. Spend the coin.
 980      //
 981      BOOST_CHECK(view->SpendCoin(outp));
 982  
 983      // The coin should be in the cache, but spent and marked dirty.
 984      BOOST_CHECK_EQUAL(GetCoinsMapEntry(view->map(), outp), SPENT_DIRTY);
 985      BOOST_CHECK(!view->HaveCoin(outp)); // Coin should be considered spent in `view`.
 986      BOOST_CHECK(base.HaveCoin(outp));  // But coin should still be unspent in `base`.
 987  
 988      flush_all(/*erase=*/ false);
 989  
 990      // Coin should be considered spent in both views.
 991      BOOST_CHECK(!view->HaveCoin(outp));
 992      BOOST_CHECK(!base.HaveCoin(outp));
 993  
 994      // Spent coin should not be spendable.
 995      BOOST_CHECK(!view->SpendCoin(outp));
 996  
 997      // --- Bonus check: ensure that a coin added to the base view via one cache
 998      //     can be spent by another cache which has never seen it.
 999      //
1000      txid = Txid::FromUint256(m_rng.rand256());
1001      outp = COutPoint(txid, 0);
1002      coin = MakeCoin();
1003      BOOST_CHECK(!base.HaveCoin(outp));
1004      BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
1005      BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
1006  
1007      all_caches[0]->AddCoin(outp, std::move(coin), false);
1008      all_caches[0]->Sync();
1009      BOOST_CHECK(base.HaveCoin(outp));
1010      BOOST_CHECK(all_caches[0]->HaveCoin(outp));
1011      BOOST_CHECK(!all_caches[1]->HaveCoinInCache(outp));
1012  
1013      BOOST_CHECK(all_caches[1]->SpendCoin(outp));
1014      flush_all(/*erase=*/ false);
1015      BOOST_CHECK(!base.HaveCoin(outp));
1016      BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
1017      BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
1018  
1019      flush_all(/*erase=*/ true); // Erase all cache content.
1020  
1021      // --- Bonus check 2: ensure that a FRESH, spent coin is deleted by Sync()
1022      //
1023      txid = Txid::FromUint256(m_rng.rand256());
1024      outp = COutPoint(txid, 0);
1025      coin = MakeCoin();
1026      CAmount coin_val = coin.out.nValue;
1027      BOOST_CHECK(!base.HaveCoin(outp));
1028      BOOST_CHECK(!all_caches[0]->HaveCoin(outp));
1029      BOOST_CHECK(!all_caches[1]->HaveCoin(outp));
1030  
1031      // Add and spend from same cache without flushing.
1032      all_caches[0]->AddCoin(outp, std::move(coin), false);
1033  
1034      // Coin should be FRESH in the cache.
1035      BOOST_CHECK_EQUAL(GetCoinsMapEntry(all_caches[0]->map(), outp), CoinEntry(coin_val, CoinEntry::State::DIRTY_FRESH));
1036      // Base shouldn't have seen coin.
1037      BOOST_CHECK(!base.HaveCoin(outp));
1038  
1039      BOOST_CHECK(all_caches[0]->SpendCoin(outp));
1040      all_caches[0]->Sync();
1041  
1042      // Ensure there is no sign of the coin after spend/flush.
1043      BOOST_CHECK(!GetCoinsMapEntry(all_caches[0]->map(), outp));
1044      BOOST_CHECK(!all_caches[0]->HaveCoinInCache(outp));
1045      BOOST_CHECK(!base.HaveCoin(outp));
1046  }
1047  }; // struct FlushTest
1048  
1049  BOOST_FIXTURE_TEST_CASE(ccoins_flush_behavior, FlushTest)
1050  {
1051      // Create two in-memory caches atop a leveldb view.
1052      CCoinsViewDB base{{.path = "test", .cache_bytes = 8_MiB, .memory_only = true}, {}};
1053      std::vector<std::unique_ptr<CCoinsViewCacheTest>> caches;
1054      caches.push_back(std::make_unique<CCoinsViewCacheTest>(&base));
1055      caches.push_back(std::make_unique<CCoinsViewCacheTest>(caches.back().get()));
1056  
1057      for (const auto& view : caches) {
1058          TestFlushBehavior(view.get(), base, caches, /*do_erasing_flush=*/false);
1059          TestFlushBehavior(view.get(), base, caches, /*do_erasing_flush=*/true);
1060      }
1061  }
1062  
1063  BOOST_AUTO_TEST_CASE(coins_resource_is_used)
1064  {
1065      CCoinsMapMemoryResource resource;
1066      PoolResourceTester::CheckAllDataAccountedFor(resource);
1067  
1068      {
1069          CCoinsMap map{0, CCoinsMap::hasher{}, CCoinsMap::key_equal{}, &resource};
1070          BOOST_TEST(memusage::DynamicUsage(map) >= resource.ChunkSizeBytes());
1071  
1072          map.reserve(1000);
1073  
1074          // The resource has preallocated a chunk, so we should have space for at several nodes without the need to allocate anything else.
1075          const auto usage_before = memusage::DynamicUsage(map);
1076  
1077          COutPoint out_point{};
1078          for (size_t i = 0; i < 1000; ++i) {
1079              out_point.n = i;
1080              map[out_point];
1081          }
1082          BOOST_TEST(usage_before == memusage::DynamicUsage(map));
1083      }
1084  
1085      PoolResourceTester::CheckAllDataAccountedFor(resource);
1086  }
1087  
1088  BOOST_AUTO_TEST_CASE(ccoins_addcoin_exception_keeps_usage_balanced)
1089  {
1090      CCoinsViewCacheTest cache{&CoinsViewEmpty::Get()};
1091  
1092      const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
1093  
1094      const Coin coin1{CTxOut{m_rng.randrange(10), CScript{} << m_rng.randbytes(CScriptBase::STATIC_SIZE + 1)}, 1, false};
1095      cache.AddCoin(outpoint, Coin{coin1}, /*possible_overwrite=*/false);
1096      cache.SelfTest();
1097  
1098      const Coin coin2{CTxOut{m_rng.randrange(20), CScript{} << m_rng.randbytes(CScriptBase::STATIC_SIZE + 2)}, 2, false};
1099      BOOST_CHECK_THROW(cache.AddCoin(outpoint, Coin{coin2}, /*possible_overwrite=*/false), std::logic_error);
1100      cache.SelfTest();
1101  
1102      BOOST_CHECK(cache.AccessCoin(outpoint) == coin1);
1103  }
1104  
1105  BOOST_AUTO_TEST_CASE(ccoins_emplace_duplicate_keeps_usage_balanced)
1106  {
1107      CCoinsViewCacheTest cache{&CoinsViewEmpty::Get()};
1108  
1109      const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
1110  
1111      const Coin coin1{CTxOut{m_rng.randrange(10), CScript{} << m_rng.randbytes(CScriptBase::STATIC_SIZE + 1)}, 1, false};
1112      cache.EmplaceCoinInternalDANGER(COutPoint{outpoint}, Coin{coin1});
1113      cache.SelfTest();
1114  
1115      const Coin coin2{CTxOut{m_rng.randrange(20), CScript{} << m_rng.randbytes(CScriptBase::STATIC_SIZE + 2)}, 2, false};
1116      cache.EmplaceCoinInternalDANGER(COutPoint{outpoint}, Coin{coin2});
1117      cache.SelfTest();
1118  
1119      BOOST_CHECK(cache.AccessCoin(outpoint) == coin1);
1120  }
1121  
1122  BOOST_AUTO_TEST_CASE(ccoins_reset_guard)
1123  {
1124      CCoinsViewTest root{m_rng};
1125      CCoinsViewCache root_cache{&root};
1126      uint256 base_best_block{m_rng.rand256()};
1127      root_cache.SetBestBlock(base_best_block);
1128      root_cache.Flush();
1129  
1130      CCoinsViewCache cache{&root};
1131  
1132      const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
1133  
1134      const Coin coin{CTxOut{m_rng.randrange(10), CScript{} << m_rng.randbytes(CScriptBase::STATIC_SIZE + 1)}, 1, false};
1135      cache.EmplaceCoinInternalDANGER(COutPoint{outpoint}, Coin{coin});
1136      BOOST_CHECK_EQUAL(cache.GetDirtyCount(), 1U);
1137  
1138      uint256 cache_best_block{m_rng.rand256()};
1139      cache.SetBestBlock(cache_best_block);
1140  
1141      {
1142          const auto reset_guard{cache.CreateResetGuard()};
1143          BOOST_CHECK(cache.AccessCoin(outpoint) == coin);
1144          BOOST_CHECK(!cache.AccessCoin(outpoint).IsSpent());
1145          BOOST_CHECK_EQUAL(cache.GetCacheSize(), 1);
1146          BOOST_CHECK_EQUAL(cache.GetDirtyCount(), 1);
1147          BOOST_CHECK_EQUAL(cache.GetBestBlock(), cache_best_block);
1148          BOOST_CHECK(!root_cache.HaveCoinInCache(outpoint));
1149      }
1150  
1151      BOOST_CHECK(cache.AccessCoin(outpoint).IsSpent());
1152      BOOST_CHECK_EQUAL(cache.GetCacheSize(), 0);
1153      BOOST_CHECK_EQUAL(cache.GetDirtyCount(), 0);
1154      BOOST_CHECK_EQUAL(cache.GetBestBlock(), base_best_block);
1155      BOOST_CHECK(!root_cache.HaveCoinInCache(outpoint));
1156  
1157      // Using a reset guard again is idempotent
1158      {
1159          const auto reset_guard{cache.CreateResetGuard()};
1160      }
1161  
1162      BOOST_CHECK(cache.AccessCoin(outpoint).IsSpent());
1163      BOOST_CHECK_EQUAL(cache.GetCacheSize(), 0);
1164      BOOST_CHECK_EQUAL(cache.GetDirtyCount(), 0U);
1165      BOOST_CHECK_EQUAL(cache.GetBestBlock(), base_best_block);
1166      BOOST_CHECK(!root_cache.HaveCoinInCache(outpoint));
1167  
1168      // Flush should be a no-op after reset.
1169      cache.Flush();
1170      BOOST_CHECK_EQUAL(cache.GetDirtyCount(), 0U);
1171  }
1172  
1173  BOOST_AUTO_TEST_CASE(ccoins_peekcoin)
1174  {
1175      CCoinsViewTest base{m_rng};
1176  
1177      // Populate the base view with a coin.
1178      const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
1179      const Coin coin{CTxOut{m_rng.randrange(10), CScript{}}, 1, false};
1180      {
1181          CCoinsViewCache cache{&base};
1182          cache.AddCoin(outpoint, Coin{coin}, /*possible_overwrite=*/false);
1183          cache.Flush();
1184      }
1185  
1186      // Verify PeekCoin can read through the cache stack without mutating the intermediate cache.
1187      CCoinsViewCacheTest main_cache{&base};
1188      const auto fetched{main_cache.PeekCoin(outpoint)};
1189      BOOST_CHECK(fetched.has_value());
1190      BOOST_CHECK(*fetched == coin);
1191      BOOST_CHECK(!main_cache.HaveCoinInCache(outpoint));
1192  }
1193  
1194  BOOST_AUTO_TEST_SUITE_END()