rbf_tests.cpp

// Copyright (c) 2021-present The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <common/system.h>
#include <policy/rbf.h>
#include <random.h>
#include <test/util/txmempool.h>
#include <txmempool.h>
#include <util/time.h>

#include <test/util/setup_common.h>

#include <boost/test/unit_test.hpp>
#include <optional>
#include <vector>

BOOST_FIXTURE_TEST_SUITE(rbf_tests, BasicTestingSetup)

static inline CTransactionRef make_tx(const std::vector<CTransactionRef>& inputs,
                                      const std::vector<CAmount>& output_values)
{
    CMutableTransaction tx = CMutableTransaction();
    tx.vin.resize(inputs.size());
    tx.vout.resize(output_values.size());
    for (size_t i = 0; i < inputs.size(); ++i) {
        tx.vin[i].prevout.hash = inputs[i]->GetHash();
        tx.vin[i].prevout.n = 0;
        // Add a witness so wtxid != txid
        CScriptWitness witness;
        witness.stack.emplace_back(i + 10);
        tx.vin[i].scriptWitness = witness;
    }
    for (size_t i = 0; i < output_values.size(); ++i) {
        tx.vout[i].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
        tx.vout[i].nValue = output_values[i];
    }
    return MakeTransactionRef(tx);
}

static CTransactionRef add_descendants(const CTransactionRef& tx, int32_t num_descendants, CTxMemPool& pool)
    EXCLUSIVE_LOCKS_REQUIRED(::cs_main, pool.cs)
{
    AssertLockHeld(::cs_main);
    AssertLockHeld(pool.cs);
    TestMemPoolEntryHelper entry;
    // Assumes this isn't already spent in mempool
    auto tx_to_spend = tx;
    for (int32_t i{0}; i < num_descendants; ++i) {
        auto next_tx = make_tx(/*inputs=*/{tx_to_spend}, /*output_values=*/{(50 - i) * CENT});
        TryAddToMempool(pool, entry.FromTx(next_tx));
        BOOST_CHECK(pool.GetIter(next_tx->GetHash()).has_value());
        tx_to_spend = next_tx;
    }
    // Return last created tx
    return tx_to_spend;
}

BOOST_FIXTURE_TEST_CASE(rbf_helper_functions, TestChain100Setup)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(::cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    const CAmount low_fee{CENT/100};
    const CAmount normal_fee{CENT/10};
    const CAmount high_fee{CENT};

    // Create a parent tx1 and child tx2 with normal fees:
    const auto tx1 = make_tx(/*inputs=*/ {m_coinbase_txns[0]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx1));
    const auto tx2 = make_tx(/*inputs=*/ {tx1}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx2));

    // Create a low-feerate parent tx3 and high-feerate child tx4 (cpfp)
    const auto tx3 = make_tx(/*inputs=*/ {m_coinbase_txns[1]}, /*output_values=*/ {1099 * CENT});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(tx3));
    const auto tx4 = make_tx(/*inputs=*/ {tx3}, /*output_values=*/ {999 * CENT});
    TryAddToMempool(pool, entry.Fee(high_fee).FromTx(tx4));

    // Create a parent tx5 and child tx6 where both have very low fees
    const auto tx5 = make_tx(/*inputs=*/ {m_coinbase_txns[2]}, /*output_values=*/ {1099 * CENT});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(tx5));
    const auto tx6 = make_tx(/*inputs=*/ {tx5}, /*output_values=*/ {1098 * CENT});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(tx6));
    // Make tx6's modified fee much higher than its base fee. This should cause it to pass
    // the fee-related checks despite being low-feerate.
    pool.PrioritiseTransaction(tx6->GetHash(), 1 * COIN);

    // Two independent high-feerate transactions, tx7 and tx8
    const auto tx7 = make_tx(/*inputs=*/ {m_coinbase_txns[3]}, /*output_values=*/ {999 * CENT});
    TryAddToMempool(pool, entry.Fee(high_fee).FromTx(tx7));
    const auto tx8 = make_tx(/*inputs=*/ {m_coinbase_txns[4]}, /*output_values=*/ {999 * CENT});
    TryAddToMempool(pool, entry.Fee(high_fee).FromTx(tx8));

    // Will make these two parents of single child
    const auto tx11 = make_tx(/*inputs=*/ {m_coinbase_txns[7]}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx11));
    const auto tx12 = make_tx(/*inputs=*/ {m_coinbase_txns[8]}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx12));

    // Will make two children of this single parent
    const auto tx13 = make_tx(/*inputs=*/ {m_coinbase_txns[9]}, /*output_values=*/ {995 * CENT, 995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx13));

    const auto entry1_normal = pool.GetIter(tx1->GetHash()).value();
    const auto entry2_normal = pool.GetIter(tx2->GetHash()).value();
    const auto entry3_low = pool.GetIter(tx3->GetHash()).value();
    const auto entry4_high = pool.GetIter(tx4->GetHash()).value();
    const auto entry5_low = pool.GetIter(tx5->GetHash()).value();
    const auto entry6_low_prioritised = pool.GetIter(tx6->GetHash()).value();
    const auto entry7_high = pool.GetIter(tx7->GetHash()).value();
    const auto entry8_high = pool.GetIter(tx8->GetHash()).value();

    BOOST_CHECK_EQUAL(entry1_normal->GetFee(), normal_fee);
    BOOST_CHECK_EQUAL(entry2_normal->GetFee(), normal_fee);
    BOOST_CHECK_EQUAL(entry3_low->GetFee(), low_fee);
    BOOST_CHECK_EQUAL(entry4_high->GetFee(), high_fee);
    BOOST_CHECK_EQUAL(entry5_low->GetFee(), low_fee);
    BOOST_CHECK_EQUAL(entry6_low_prioritised->GetFee(), low_fee);
    BOOST_CHECK_EQUAL(entry7_high->GetFee(), high_fee);
    BOOST_CHECK_EQUAL(entry8_high->GetFee(), high_fee);

    CTxMemPool::setEntries set_12_normal{entry1_normal, entry2_normal};
    CTxMemPool::setEntries set_34_cpfp{entry3_low, entry4_high};
    CTxMemPool::setEntries set_56_low{entry5_low, entry6_low_prioritised};
    CTxMemPool::setEntries set_78_high{entry7_high, entry8_high};
    CTxMemPool::setEntries all_entries{entry1_normal, entry2_normal, entry3_low, entry4_high,
                                       entry5_low, entry6_low_prioritised, entry7_high, entry8_high};
    CTxMemPool::setEntries empty_set;

    const auto unused_txid = Txid::FromUint256(GetRandHash());

    // Tests for EntriesAndTxidsDisjoint
    BOOST_CHECK(EntriesAndTxidsDisjoint(empty_set, {tx1->GetHash()}, unused_txid) == std::nullopt);
    BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx3->GetHash()}, unused_txid) == std::nullopt);
    BOOST_CHECK(EntriesAndTxidsDisjoint({entry2_normal}, {tx2->GetHash()}, unused_txid).has_value());
    BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx1->GetHash()}, unused_txid).has_value());
    BOOST_CHECK(EntriesAndTxidsDisjoint(set_12_normal, {tx2->GetHash()}, unused_txid).has_value());
    // EntriesAndTxidsDisjoint does not calculate descendants of iters_conflicting; it uses whatever
    // the caller passed in. As such, no error is returned even though entry2_normal is a descendant of tx1.
    BOOST_CHECK(EntriesAndTxidsDisjoint({entry2_normal}, {tx1->GetHash()}, unused_txid) == std::nullopt);

    // Tests for PaysForRBF
    const CFeeRate incremental_relay_feerate{DEFAULT_INCREMENTAL_RELAY_FEE};
    const CFeeRate higher_relay_feerate{2 * DEFAULT_INCREMENTAL_RELAY_FEE};
    // Must pay at least as much as the original.
    BOOST_CHECK(PaysForRBF(/*original_fees=*/high_fee,
                           /*replacement_fees=*/high_fee,
                           /*replacement_vsize=*/1,
                           /*relay_fee=*/CFeeRate(0),
                           /*txid=*/unused_txid)
                           == std::nullopt);
    BOOST_CHECK(PaysForRBF(high_fee, high_fee - 1, 1, CFeeRate(0), unused_txid).has_value());
    BOOST_CHECK(PaysForRBF(high_fee + 1, high_fee, 1, CFeeRate(0), unused_txid).has_value());
    // Additional fees must cover the replacement's vsize at incremental relay fee
    BOOST_CHECK(PaysForRBF(high_fee, high_fee + 1, 11, incremental_relay_feerate, unused_txid).has_value());
    BOOST_CHECK(PaysForRBF(high_fee, high_fee + 1, 10, incremental_relay_feerate, unused_txid) == std::nullopt);
    BOOST_CHECK(PaysForRBF(high_fee, high_fee + 2, 11, higher_relay_feerate, unused_txid).has_value());
    BOOST_CHECK(PaysForRBF(high_fee, high_fee + 4, 20, higher_relay_feerate, unused_txid) == std::nullopt);
    BOOST_CHECK(PaysForRBF(low_fee, high_fee, 99999999, incremental_relay_feerate, unused_txid).has_value());
    BOOST_CHECK(PaysForRBF(low_fee, high_fee + 99999999, 99999999, incremental_relay_feerate, unused_txid) == std::nullopt);
}

BOOST_FIXTURE_TEST_CASE(rbf_conflicts_calculator, TestChain100Setup)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(::cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    const CAmount normal_fee{CENT/10};

    // Create two parent transactions with 51 outputs each
    const int NUM_OUTPUTS = 51;
    std::vector<CAmount> output_values;
    output_values.reserve(NUM_OUTPUTS);
    for (int i = 0; i < NUM_OUTPUTS; ++i) {
        output_values.push_back(1 * COIN);
    }

    const auto parent_tx_1 = make_tx(/*inputs=*/ {m_coinbase_txns[0]}, /*output_values=*/ output_values);
    const auto parent_tx_2 = make_tx(/*inputs=*/ {m_coinbase_txns[1]}, /*output_values=*/ output_values);
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(parent_tx_1));
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(parent_tx_2));

    std::vector<CTransactionRef> direct_children;

    // Create individual spends of these outputs
    for (const auto& parent_tx : {parent_tx_1, parent_tx_2}) {
        for (auto i = 0; i < NUM_OUTPUTS; ++i) {
            auto pretx = make_tx(/*inputs=*/ {parent_tx}, /*output_values=*/ {995 * CENT});
            CMutableTransaction tx(*pretx);
            tx.vin[0].prevout.n = i;
            TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx));
            BOOST_CHECK(pool.GetIter(tx.GetHash()).has_value());
            direct_children.push_back(MakeTransactionRef(tx));
        }
    }

    // At this point, we should have 2 clusters in the mempool, each with 52
    // transactions.

    // parent_tx and all children are in one cluster, so we can have as many
    // conflicts within this cluster as we want without violating the RBF conflicts
    // limit.
    const auto parent_entry_1 = pool.GetIter(parent_tx_1->GetHash()).value();
    const auto parent_entry_2 = pool.GetIter(parent_tx_2->GetHash()).value();
    const auto conflicting_transaction = make_tx({parent_tx_1, parent_tx_2}, {50 * CENT});
    CTxMemPool::setEntries all_conflicts, dummy;
    BOOST_CHECK(GetEntriesForConflicts(/*tx=*/ *conflicting_transaction.get(),
                                       /*pool=*/ pool,
                                       /*iters_conflicting=*/ {parent_entry_1, parent_entry_2},
                                       /*all_conflicts=*/ all_conflicts) == std::nullopt);

    dummy.clear();
    // Conflicting directly with all those conflicts doesn't change anything.
    BOOST_CHECK(GetEntriesForConflicts(/*tx=*/ *conflicting_transaction.get(),
                                       /*pool=*/ pool,
                                       /*iters_conflicting=*/ all_conflicts,
                                       /*all_conflicts=*/ dummy) == std::nullopt);
    BOOST_CHECK_EQUAL(all_conflicts.size(), dummy.size());
    dummy.clear();

    // If we mine the parent_tx's, then the clusters split (102 clusters).
    pool.removeForBlock({parent_tx_1, parent_tx_2}, /*nBlockHeight=*/ 1);

    // Add some descendants now to each of the direct children (we can do this now that the clusters have split).
    for (const auto& child : direct_children) {
        add_descendants(child, 10, pool);
    }

    // We can conflict with 100 different clusters, even if they have lots of transactions.
    CTxMemPool::setEntries conflicts;
    for (auto i = 0; i < 100; ++i) {
        conflicts.insert(pool.GetIter(direct_children[i]->GetHash()).value());
    }
    BOOST_CHECK(GetEntriesForConflicts(/*tx=*/ *conflicting_transaction.get(),
                                       /*pool=*/ pool,
                                       /*iters_conflicting=*/ conflicts,
                                       /*all_conflicts=*/ dummy) == std::nullopt);

    // Conflicting with 1 more distinct cluster causes failure, however.
    conflicts.insert(pool.GetIter(direct_children[100]->GetHash()).value());
    BOOST_CHECK(GetEntriesForConflicts(/*tx=*/ *conflicting_transaction.get(),
                                       /*pool=*/ pool,
                                       /*iters_conflicting=*/ conflicts,
                                       /*all_conflicts=*/ dummy).has_value());
}

BOOST_FIXTURE_TEST_CASE(improves_feerate, TestChain100Setup)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(::cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    const CAmount low_fee{CENT/100};
    const CAmount normal_fee{CENT/10};

    // low feerate parent with normal feerate child
    const auto tx1 = make_tx(/*inputs=*/ {m_coinbase_txns[0], m_coinbase_txns[1]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(tx1));
    const auto tx2 = make_tx(/*inputs=*/ {tx1}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx2));

    const auto entry1 = pool.GetIter(tx1->GetHash()).value();
    const auto tx1_fee = entry1->GetModifiedFee();
    const auto entry2 = pool.GetIter(tx2->GetHash()).value();
    const auto tx2_fee = entry2->GetModifiedFee();

    // conflicting transactions
    const auto tx1_conflict = make_tx(/*inputs=*/ {m_coinbase_txns[0], m_coinbase_txns[2]}, /*output_values=*/ {10 * COIN});
    const auto tx3 = make_tx(/*inputs=*/ {tx1_conflict}, /*output_values=*/ {995 * CENT});
    auto entry3 = entry.FromTx(tx3);

    // Now test ImprovesFeerateDiagram with various levels of "package rbf" feerates

    // It doesn't improve itself
    auto changeset = pool.GetChangeSet();
    changeset->StageRemoval(entry1);
    changeset->StageRemoval(entry2);
    changeset->StageAddition(tx1_conflict, tx1_fee, 0, 1, 0, false, 4, LockPoints());
    changeset->StageAddition(tx3, tx2_fee, 0, 1, 0, false, 4, LockPoints());
    const auto res1 = ImprovesFeerateDiagram(*changeset);
    BOOST_CHECK(res1.has_value());
    BOOST_CHECK(res1.value().first == DiagramCheckError::FAILURE);
    BOOST_CHECK(res1.value().second == "insufficient feerate: does not improve feerate diagram");

    // With one more satoshi it does
    changeset.reset();
    changeset = pool.GetChangeSet();
    changeset->StageRemoval(entry1);
    changeset->StageRemoval(entry2);
    changeset->StageAddition(tx1_conflict, tx1_fee+1, 0, 1, 0, false, 4, LockPoints());
    changeset->StageAddition(tx3, tx2_fee, 0, 1, 0, false, 4, LockPoints());
    BOOST_CHECK(ImprovesFeerateDiagram(*changeset) == std::nullopt);

    changeset.reset();
    // With prioritisation of in-mempool conflicts, it affects the results of the comparison using the same args as just above
    pool.PrioritiseTransaction(entry1->GetSharedTx()->GetHash(), /*nFeeDelta=*/1);
    changeset = pool.GetChangeSet();
    changeset->StageRemoval(entry1);
    changeset->StageRemoval(entry2);
    changeset->StageAddition(tx1_conflict, tx1_fee+1, 0, 1, 0, false, 4, LockPoints());
    changeset->StageAddition(tx3, tx2_fee, 0, 1, 0, false, 4, LockPoints());
    const auto res2 = ImprovesFeerateDiagram(*changeset);
    BOOST_CHECK(res2.has_value());
    BOOST_CHECK(res2.value().first == DiagramCheckError::FAILURE);
    BOOST_CHECK(res2.value().second == "insufficient feerate: does not improve feerate diagram");
    changeset.reset();

    pool.PrioritiseTransaction(entry1->GetSharedTx()->GetHash(), /*nFeeDelta=*/-1);

    // With fewer vbytes it does
    CMutableTransaction tx4{entry3.GetTx()};
    tx4.vin[0].scriptWitness = CScriptWitness(); // Clear out the witness, to reduce size
    auto entry4 = entry.FromTx(MakeTransactionRef(tx4));
    changeset = pool.GetChangeSet();
    changeset->StageRemoval(entry1);
    changeset->StageRemoval(entry2);
    changeset->StageAddition(tx1_conflict, tx1_fee, 0, 1, 0, false, 4, LockPoints());
    changeset->StageAddition(entry4.GetSharedTx(), tx2_fee, 0, 1, 0, false, 4, LockPoints());
    BOOST_CHECK(ImprovesFeerateDiagram(*changeset) == std::nullopt);
    changeset.reset();

    // Adding a grandchild makes the cluster size 3, which is also calculable
    const auto tx5 = make_tx(/*inputs=*/ {tx2}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(normal_fee).FromTx(tx5));
    const auto entry5 = pool.GetIter(tx5->GetHash()).value();

    changeset = pool.GetChangeSet();
    changeset->StageRemoval(entry1);
    changeset->StageRemoval(entry2);
    changeset->StageRemoval(entry5);
    changeset->StageAddition(tx1_conflict, tx1_fee, 0, 1, 0, false, 4, LockPoints());
    changeset->StageAddition(entry4.GetSharedTx(), tx2_fee + entry5->GetModifiedFee() + 1, 0, 1, 0, false, 4, LockPoints());
    const auto res3 = ImprovesFeerateDiagram(*changeset);
    BOOST_CHECK(res3 == std::nullopt);
}

BOOST_FIXTURE_TEST_CASE(calc_feerate_diagram_rbf, TestChain100Setup)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(::cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    const CAmount low_fee{CENT/100};
    const CAmount high_fee{CENT};

    // low -> high -> medium fee transactions that would result in two chunks together since they
    // are all same size
    const auto low_tx = make_tx(/*inputs=*/ {m_coinbase_txns[0]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(low_tx));

    const auto entry_low = pool.GetIter(low_tx->GetHash()).value();
    const auto low_size = entry_low->GetAdjustedWeight();

    const auto replacement_tx = make_tx(/*inputs=*/ {m_coinbase_txns[0]}, /*output_values=*/ {9 * COIN});
    auto entry_replacement = entry.FromTx(replacement_tx);

    // Replacement of size 1
    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(entry_low);
        changeset->StageAddition(replacement_tx, 0, 0, 1, 0, false, 4, LockPoints());
        const auto replace_one{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_one.has_value());
        std::vector<FeeFrac> expected_old_chunks{{low_fee, low_size}};
        BOOST_CHECK(replace_one->first == expected_old_chunks);
        std::vector<FeeFrac> expected_new_chunks{{0, entry_replacement.GetAdjustedWeight()}};
        BOOST_CHECK(replace_one->second == expected_new_chunks);
    }

    // Non-zero replacement fee/size
    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(entry_low);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_one_fee{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_one_fee.has_value());
        std::vector<FeeFrac> expected_old_diagram{{low_fee, low_size}};
        BOOST_CHECK(replace_one_fee->first == expected_old_diagram);
        std::vector<FeeFrac> expected_new_diagram{{high_fee, entry_replacement.GetAdjustedWeight()}};
        BOOST_CHECK(replace_one_fee->second == expected_new_diagram);
    }

    // Add a second transaction to the cluster that will make a single chunk, to be evicted in the RBF
    const auto high_tx = make_tx(/*inputs=*/ {low_tx}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(high_fee).FromTx(high_tx));
    const auto entry_high = pool.GetIter(high_tx->GetHash()).value();
    const auto high_size = entry_high->GetAdjustedWeight();

    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(entry_low);
        changeset->StageRemoval(entry_high);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_single_chunk{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_single_chunk.has_value());
        std::vector<FeeFrac> expected_old_chunks{{low_fee + high_fee, low_size + high_size}};
        BOOST_CHECK(replace_single_chunk->first == expected_old_chunks);
        std::vector<FeeFrac> expected_new_chunks{{high_fee, entry_replacement.GetAdjustedWeight()}};
        BOOST_CHECK(replace_single_chunk->second == expected_new_chunks);
    }

    // Conflict with the 2nd tx, resulting in new diagram with three entries
    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(entry_high);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_cpfp_child{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_cpfp_child.has_value());
        std::vector<FeeFrac> expected_old_chunks{{low_fee + high_fee, low_size + high_size}};
        BOOST_CHECK(replace_cpfp_child->first == expected_old_chunks);
        std::vector<FeeFrac> expected_new_chunks{{high_fee, entry_replacement.GetAdjustedWeight()}, {low_fee, low_size}};
        BOOST_CHECK(replace_cpfp_child->second == expected_new_chunks);
    }

    // Make a size 2 cluster that is itself two chunks; evict both txns
    const auto high_tx_2 = make_tx(/*inputs=*/ {m_coinbase_txns[1]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(high_fee).FromTx(high_tx_2));
    const auto entry_high_2 = pool.GetIter(high_tx_2->GetHash()).value();
    const auto high_size_2 = entry_high_2->GetAdjustedWeight();

    const auto low_tx_2 = make_tx(/*inputs=*/ {high_tx_2}, /*output_values=*/ {9 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(low_tx_2));
    const auto entry_low_2 = pool.GetIter(low_tx_2->GetHash()).value();
    const auto low_size_2 = entry_low_2->GetAdjustedWeight();

    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(entry_high_2);
        changeset->StageRemoval(entry_low_2);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_two_chunks_single_cluster{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_two_chunks_single_cluster.has_value());
        std::vector<FeeFrac> expected_old_chunks{{high_fee, high_size_2}, {low_fee, low_size_2}};
        BOOST_CHECK(replace_two_chunks_single_cluster->first == expected_old_chunks);
        std::vector<FeeFrac> expected_new_chunks{{high_fee, low_size_2}};
        BOOST_CHECK(replace_two_chunks_single_cluster->second == expected_new_chunks);
    }

    // You can have more than two direct conflicts
    const auto conflict_1 = make_tx(/*inputs=*/ {m_coinbase_txns[2]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(conflict_1));
    const auto conflict_1_entry = pool.GetIter(conflict_1->GetHash()).value();

    const auto conflict_2 = make_tx(/*inputs=*/ {m_coinbase_txns[3]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(conflict_2));
    const auto conflict_2_entry = pool.GetIter(conflict_2->GetHash()).value();

    const auto conflict_3 = make_tx(/*inputs=*/ {m_coinbase_txns[4]}, /*output_values=*/ {10 * COIN});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(conflict_3));
    const auto conflict_3_entry = pool.GetIter(conflict_3->GetHash()).value();

    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(conflict_1_entry);
        changeset->StageRemoval(conflict_2_entry);
        changeset->StageRemoval(conflict_3_entry);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_multiple_clusters{changeset->CalculateChunksForRBF()};
        BOOST_CHECK(replace_multiple_clusters.has_value());
        BOOST_CHECK(replace_multiple_clusters->first.size() == 3);
        BOOST_CHECK(replace_multiple_clusters->second.size() == 1);
    }

    // Add a child transaction to conflict_1 and make it cluster size 2, two chunks due to same feerate
    const auto conflict_1_child = make_tx(/*inputs=*/{conflict_1}, /*output_values=*/ {995 * CENT});
    TryAddToMempool(pool, entry.Fee(low_fee).FromTx(conflict_1_child));
    const auto conflict_1_child_entry = pool.GetIter(conflict_1_child->GetHash()).value();

    {
        auto changeset = pool.GetChangeSet();
        changeset->StageRemoval(conflict_1_entry);
        changeset->StageRemoval(conflict_2_entry);
        changeset->StageRemoval(conflict_3_entry);
        changeset->StageRemoval(conflict_1_child_entry);
        changeset->StageAddition(replacement_tx, high_fee, 0, 1, 0, false, 4, LockPoints());
        const auto replace_multiple_clusters_2{changeset->CalculateChunksForRBF()};

        BOOST_CHECK(replace_multiple_clusters_2.has_value());
        BOOST_CHECK(replace_multiple_clusters_2->first.size() == 4);
        BOOST_CHECK(replace_multiple_clusters_2->second.size() == 1);
    }
}

BOOST_AUTO_TEST_CASE(feerate_chunks_utilities)
{
    // Sanity check the correctness of the feerate chunks comparison.

    // A strictly better case.
    std::vector<FeeFrac> old_chunks{{{950, 300}, {100, 100}}};
    std::vector<FeeFrac> new_chunks{{{1000, 300}, {50, 100}}};

    BOOST_CHECK(std::is_lt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_gt(CompareChunks(new_chunks, old_chunks)));

    // Incomparable diagrams
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{1000, 300}, {0, 100}};

    BOOST_CHECK(CompareChunks(old_chunks, new_chunks) == std::partial_ordering::unordered);
    BOOST_CHECK(CompareChunks(new_chunks, old_chunks) == std::partial_ordering::unordered);

    // Strictly better but smaller size.
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{1100, 300}};

    BOOST_CHECK(std::is_lt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_gt(CompareChunks(new_chunks, old_chunks)));

    // New diagram is strictly better due to the first chunk, even though
    // second chunk contributes no fees
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{1100, 100}, {0, 100}};

    BOOST_CHECK(std::is_lt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_gt(CompareChunks(new_chunks, old_chunks)));

    // Feerate of first new chunk is better with, but second chunk is worse
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{750, 100}, {249, 250}, {151, 650}};

    BOOST_CHECK(CompareChunks(old_chunks, new_chunks) == std::partial_ordering::unordered);
    BOOST_CHECK(CompareChunks(new_chunks, old_chunks) == std::partial_ordering::unordered);

    // If we make the second chunk slightly better, the new diagram now wins.
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{750, 100}, {250, 250}, {150, 150}};

    BOOST_CHECK(std::is_lt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_gt(CompareChunks(new_chunks, old_chunks)));

    // Identical diagrams, cannot be strictly better
    old_chunks = {{950, 300}, {100, 100}};
    new_chunks = {{950, 300}, {100, 100}};

    BOOST_CHECK(std::is_eq(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_eq(CompareChunks(new_chunks, old_chunks)));

    // Same aggregate fee, but different total size (trigger single tail fee check step)
    old_chunks = {{950, 300}, {100, 99}};
    new_chunks = {{950, 300}, {100, 100}};

    // No change in evaluation when tail check needed.
    BOOST_CHECK(std::is_gt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_lt(CompareChunks(new_chunks, old_chunks)));

    // Trigger multiple tail fee check steps
    old_chunks = {{950, 300}, {100, 99}};
    new_chunks = {{950, 300}, {100, 100}, {0, 1}, {0, 1}};

    BOOST_CHECK(std::is_gt(CompareChunks(old_chunks, new_chunks)));
    BOOST_CHECK(std::is_lt(CompareChunks(new_chunks, old_chunks)));

    // Multiple tail fee check steps, unordered result
    new_chunks = {{950, 300}, {100, 100}, {0, 1}, {0, 1}, {1, 1}};
    BOOST_CHECK(CompareChunks(old_chunks, new_chunks) == std::partial_ordering::unordered);
    BOOST_CHECK(CompareChunks(new_chunks, old_chunks) == std::partial_ordering::unordered);
}

BOOST_AUTO_TEST_SUITE_END()