mempool_tests.cpp

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// Copyright (c) 2011-2021 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 <policy/policy.h>
#include <txmempool.h>
#include <util/system.h>
#include <util/time.h>

#include <test/util/setup_common.h>

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

BOOST_FIXTURE_TEST_SUITE(mempool_tests, TestingSetup)

static constexpr auto REMOVAL_REASON_DUMMY = MemPoolRemovalReason::REPLACED;

class MemPoolTest final : public CTxMemPool
{
public:
    using CTxMemPool::GetMinFee;
};

BOOST_AUTO_TEST_CASE(MempoolRemoveTest)
{
    // Test CTxMemPool::remove functionality

    TestMemPoolEntryHelper entry;
    // Parent transaction with three children,
    // and three grand-children:
    CMutableTransaction txParent;
    txParent.vin.resize(1);
    txParent.vin[0].scriptSig = CScript() << OP_11;
    txParent.vout.resize(3);
    for (int i = 0; i < 3; i++)
    {
        txParent.vout[i].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
        txParent.vout[i].nValue = 33000LL;
    }
    CMutableTransaction txChild[3];
    for (int i = 0; i < 3; i++)
    {
        txChild[i].vin.resize(1);
        txChild[i].vin[0].scriptSig = CScript() << OP_11;
        txChild[i].vin[0].prevout.hash = txParent.GetHash();
        txChild[i].vin[0].prevout.n = i;
        txChild[i].vout.resize(1);
        txChild[i].vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
        txChild[i].vout[0].nValue = 11000LL;
    }
    CMutableTransaction txGrandChild[3];
    for (int i = 0; i < 3; i++)
    {
        txGrandChild[i].vin.resize(1);
        txGrandChild[i].vin[0].scriptSig = CScript() << OP_11;
        txGrandChild[i].vin[0].prevout.hash = txChild[i].GetHash();
        txGrandChild[i].vin[0].prevout.n = 0;
        txGrandChild[i].vout.resize(1);
        txGrandChild[i].vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
        txGrandChild[i].vout[0].nValue = 11000LL;
    }


    CTxMemPool& testPool = *Assert(m_node.mempool);
    LOCK2(cs_main, testPool.cs);

    // Nothing in pool, remove should do nothing:
    unsigned int poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txParent), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize);

    // Just the parent:
    testPool.addUnchecked(entry.FromTx(txParent));
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txParent), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize - 1);

    // Parent, children, grandchildren:
    testPool.addUnchecked(entry.FromTx(txParent));
    for (int i = 0; i < 3; i++)
    {
        testPool.addUnchecked(entry.FromTx(txChild[i]));
        testPool.addUnchecked(entry.FromTx(txGrandChild[i]));
    }
    // Remove Child[0], GrandChild[0] should be removed:
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txChild[0]), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize - 2);
    // ... make sure grandchild and child are gone:
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txGrandChild[0]), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize);
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txChild[0]), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize);
    // Remove parent, all children/grandchildren should go:
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txParent), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize - 5);
    BOOST_CHECK_EQUAL(testPool.size(), 0U);

    // Add children and grandchildren, but NOT the parent (simulate the parent being in a block)
    for (int i = 0; i < 3; i++)
    {
        testPool.addUnchecked(entry.FromTx(txChild[i]));
        testPool.addUnchecked(entry.FromTx(txGrandChild[i]));
    }
    // Now remove the parent, as might happen if a block-re-org occurs but the parent cannot be
    // put into the mempool (maybe because it is non-standard):
    poolSize = testPool.size();
    testPool.removeRecursive(CTransaction(txParent), REMOVAL_REASON_DUMMY);
    BOOST_CHECK_EQUAL(testPool.size(), poolSize - 6);
    BOOST_CHECK_EQUAL(testPool.size(), 0U);
}

template <typename name>
static void CheckSort(CTxMemPool& pool, std::vector<std::string>& sortedOrder) EXCLUSIVE_LOCKS_REQUIRED(pool.cs)
{
    BOOST_CHECK_EQUAL(pool.size(), sortedOrder.size());
    typename CTxMemPool::indexed_transaction_set::index<name>::type::iterator it = pool.mapTx.get<name>().begin();
    int count = 0;
    for (; it != pool.mapTx.get<name>().end(); ++it, ++count) {
        BOOST_CHECK_EQUAL(it->GetTx().GetHash().ToString(), sortedOrder[count]);
    }
}

BOOST_AUTO_TEST_CASE(MempoolIndexingTest)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    /* 3rd highest fee */
    CMutableTransaction tx1 = CMutableTransaction();
    tx1.vout.resize(1);
    tx1.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx1.vout[0].nValue = 10 * COIN;
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx1));

    /* highest fee */
    CMutableTransaction tx2 = CMutableTransaction();
    tx2.vout.resize(1);
    tx2.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx2.vout[0].nValue = 2 * COIN;
    pool.addUnchecked(entry.Fee(20000LL).FromTx(tx2));

    /* lowest fee */
    CMutableTransaction tx3 = CMutableTransaction();
    tx3.vout.resize(1);
    tx3.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx3.vout[0].nValue = 5 * COIN;
    pool.addUnchecked(entry.Fee(0LL).FromTx(tx3));

    /* 2nd highest fee */
    CMutableTransaction tx4 = CMutableTransaction();
    tx4.vout.resize(1);
    tx4.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx4.vout[0].nValue = 6 * COIN;
    pool.addUnchecked(entry.Fee(15000LL).FromTx(tx4));

    /* equal fee rate to tx1, but newer */
    CMutableTransaction tx5 = CMutableTransaction();
    tx5.vout.resize(1);
    tx5.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx5.vout[0].nValue = 11 * COIN;
    entry.nTime = 1;
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx5));
    BOOST_CHECK_EQUAL(pool.size(), 5U);

    std::vector<std::string> sortedOrder;
    sortedOrder.resize(5);
    sortedOrder[0] = tx3.GetHash().ToString(); // 0
    sortedOrder[1] = tx5.GetHash().ToString(); // 10000
    sortedOrder[2] = tx1.GetHash().ToString(); // 10000
    sortedOrder[3] = tx4.GetHash().ToString(); // 15000
    sortedOrder[4] = tx2.GetHash().ToString(); // 20000
    CheckSort<descendant_score>(pool, sortedOrder);

    /* low fee but with high fee child */
    /* tx6 -> tx7 -> tx8, tx9 -> tx10 */
    CMutableTransaction tx6 = CMutableTransaction();
    tx6.vout.resize(1);
    tx6.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx6.vout[0].nValue = 20 * COIN;
    pool.addUnchecked(entry.Fee(0LL).FromTx(tx6));
    BOOST_CHECK_EQUAL(pool.size(), 6U);
    // Check that at this point, tx6 is sorted low
    sortedOrder.insert(sortedOrder.begin(), tx6.GetHash().ToString());
    CheckSort<descendant_score>(pool, sortedOrder);

    CTxMemPool::setEntries setAncestors;
    setAncestors.insert(pool.mapTx.find(tx6.GetHash()));
    CMutableTransaction tx7 = CMutableTransaction();
    tx7.vin.resize(1);
    tx7.vin[0].prevout = COutPoint(tx6.GetHash(), 0);
    tx7.vin[0].scriptSig = CScript() << OP_11;
    tx7.vout.resize(2);
    tx7.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx7.vout[0].nValue = 10 * COIN;
    tx7.vout[1].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx7.vout[1].nValue = 1 * COIN;

    CTxMemPool::setEntries setAncestorsCalculated;
    std::string dummy;
    BOOST_CHECK_EQUAL(pool.CalculateMemPoolAncestors(entry.Fee(2000000LL).FromTx(tx7), setAncestorsCalculated, 100, 1000000, 1000, 1000000, dummy), true);
    BOOST_CHECK(setAncestorsCalculated == setAncestors);

    pool.addUnchecked(entry.FromTx(tx7), setAncestors);
    BOOST_CHECK_EQUAL(pool.size(), 7U);

    // Now tx6 should be sorted higher (high fee child): tx7, tx6, tx2, ...
    sortedOrder.erase(sortedOrder.begin());
    sortedOrder.push_back(tx6.GetHash().ToString());
    sortedOrder.push_back(tx7.GetHash().ToString());
    CheckSort<descendant_score>(pool, sortedOrder);

    /* low fee child of tx7 */
    CMutableTransaction tx8 = CMutableTransaction();
    tx8.vin.resize(1);
    tx8.vin[0].prevout = COutPoint(tx7.GetHash(), 0);
    tx8.vin[0].scriptSig = CScript() << OP_11;
    tx8.vout.resize(1);
    tx8.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx8.vout[0].nValue = 10 * COIN;
    setAncestors.insert(pool.mapTx.find(tx7.GetHash()));
    pool.addUnchecked(entry.Fee(0LL).Time(2).FromTx(tx8), setAncestors);

    // Now tx8 should be sorted low, but tx6/tx both high
    sortedOrder.insert(sortedOrder.begin(), tx8.GetHash().ToString());
    CheckSort<descendant_score>(pool, sortedOrder);

    /* low fee child of tx7 */
    CMutableTransaction tx9 = CMutableTransaction();
    tx9.vin.resize(1);
    tx9.vin[0].prevout = COutPoint(tx7.GetHash(), 1);
    tx9.vin[0].scriptSig = CScript() << OP_11;
    tx9.vout.resize(1);
    tx9.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx9.vout[0].nValue = 1 * COIN;
    pool.addUnchecked(entry.Fee(0LL).Time(3).FromTx(tx9), setAncestors);

    // tx9 should be sorted low
    BOOST_CHECK_EQUAL(pool.size(), 9U);
    sortedOrder.insert(sortedOrder.begin(), tx9.GetHash().ToString());
    CheckSort<descendant_score>(pool, sortedOrder);

    std::vector<std::string> snapshotOrder = sortedOrder;

    setAncestors.insert(pool.mapTx.find(tx8.GetHash()));
    setAncestors.insert(pool.mapTx.find(tx9.GetHash()));
    /* tx10 depends on tx8 and tx9 and has a high fee*/
    CMutableTransaction tx10 = CMutableTransaction();
    tx10.vin.resize(2);
    tx10.vin[0].prevout = COutPoint(tx8.GetHash(), 0);
    tx10.vin[0].scriptSig = CScript() << OP_11;
    tx10.vin[1].prevout = COutPoint(tx9.GetHash(), 0);
    tx10.vin[1].scriptSig = CScript() << OP_11;
    tx10.vout.resize(1);
    tx10.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx10.vout[0].nValue = 10 * COIN;

    setAncestorsCalculated.clear();
    BOOST_CHECK_EQUAL(pool.CalculateMemPoolAncestors(entry.Fee(200000LL).Time(4).FromTx(tx10), setAncestorsCalculated, 100, 1000000, 1000, 1000000, dummy), true);
    BOOST_CHECK(setAncestorsCalculated == setAncestors);

    pool.addUnchecked(entry.FromTx(tx10), setAncestors);

    sortedOrder.erase(sortedOrder.begin(), sortedOrder.begin()+2); // take out tx9, tx8 from the beginning
    sortedOrder.insert(sortedOrder.begin()+5, tx9.GetHash().ToString());
    sortedOrder.insert(sortedOrder.begin()+6, tx8.GetHash().ToString());
    sortedOrder.insert(sortedOrder.begin()+7, tx10.GetHash().ToString()); // tx10 is just before tx6
    CheckSort<descendant_score>(pool, sortedOrder);

    // there should be 10 transactions in the mempool
    BOOST_CHECK_EQUAL(pool.size(), 10U);

    // Now try removing tx10 and verify the sort order returns to normal
    pool.removeRecursive(pool.mapTx.find(tx10.GetHash())->GetTx(), REMOVAL_REASON_DUMMY);
    CheckSort<descendant_score>(pool, snapshotOrder);

    pool.removeRecursive(pool.mapTx.find(tx9.GetHash())->GetTx(), REMOVAL_REASON_DUMMY);
    pool.removeRecursive(pool.mapTx.find(tx8.GetHash())->GetTx(), REMOVAL_REASON_DUMMY);
}

BOOST_AUTO_TEST_CASE(MempoolAncestorIndexingTest)
{
    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    /* 3rd highest fee */
    CMutableTransaction tx1 = CMutableTransaction();
    tx1.vout.resize(1);
    tx1.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx1.vout[0].nValue = 10 * COIN;
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx1));

    /* highest fee */
    CMutableTransaction tx2 = CMutableTransaction();
    tx2.vout.resize(1);
    tx2.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx2.vout[0].nValue = 2 * COIN;
    pool.addUnchecked(entry.Fee(20000LL).FromTx(tx2));
    uint64_t tx2Size = GetVirtualTransactionSize(CTransaction(tx2));

    /* lowest fee */
    CMutableTransaction tx3 = CMutableTransaction();
    tx3.vout.resize(1);
    tx3.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx3.vout[0].nValue = 5 * COIN;
    pool.addUnchecked(entry.Fee(0LL).FromTx(tx3));

    /* 2nd highest fee */
    CMutableTransaction tx4 = CMutableTransaction();
    tx4.vout.resize(1);
    tx4.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx4.vout[0].nValue = 6 * COIN;
    pool.addUnchecked(entry.Fee(15000LL).FromTx(tx4));

    /* equal fee rate to tx1, but newer */
    CMutableTransaction tx5 = CMutableTransaction();
    tx5.vout.resize(1);
    tx5.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx5.vout[0].nValue = 11 * COIN;
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx5));
    BOOST_CHECK_EQUAL(pool.size(), 5U);

    std::vector<std::string> sortedOrder;
    sortedOrder.resize(5);
    sortedOrder[0] = tx2.GetHash().ToString(); // 20000
    sortedOrder[1] = tx4.GetHash().ToString(); // 15000
    // tx1 and tx5 are both 10000
    // Ties are broken by hash, not timestamp, so determine which
    // hash comes first.
    if (tx1.GetHash() < tx5.GetHash()) {
        sortedOrder[2] = tx1.GetHash().ToString();
        sortedOrder[3] = tx5.GetHash().ToString();
    } else {
        sortedOrder[2] = tx5.GetHash().ToString();
        sortedOrder[3] = tx1.GetHash().ToString();
    }
    sortedOrder[4] = tx3.GetHash().ToString(); // 0

    CheckSort<ancestor_score>(pool, sortedOrder);

    /* low fee parent with high fee child */
    /* tx6 (0) -> tx7 (high) */
    CMutableTransaction tx6 = CMutableTransaction();
    tx6.vout.resize(1);
    tx6.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx6.vout[0].nValue = 20 * COIN;
    uint64_t tx6Size = GetVirtualTransactionSize(CTransaction(tx6));

    pool.addUnchecked(entry.Fee(0LL).FromTx(tx6));
    BOOST_CHECK_EQUAL(pool.size(), 6U);
    // Ties are broken by hash
    if (tx3.GetHash() < tx6.GetHash())
        sortedOrder.push_back(tx6.GetHash().ToString());
    else
        sortedOrder.insert(sortedOrder.end()-1,tx6.GetHash().ToString());

    CheckSort<ancestor_score>(pool, sortedOrder);

    CMutableTransaction tx7 = CMutableTransaction();
    tx7.vin.resize(1);
    tx7.vin[0].prevout = COutPoint(tx6.GetHash(), 0);
    tx7.vin[0].scriptSig = CScript() << OP_11;
    tx7.vout.resize(1);
    tx7.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx7.vout[0].nValue = 10 * COIN;
    uint64_t tx7Size = GetVirtualTransactionSize(CTransaction(tx7));

    /* set the fee to just below tx2's feerate when including ancestor */
    CAmount fee = (20000/tx2Size)*(tx7Size + tx6Size) - 1;

    pool.addUnchecked(entry.Fee(fee).FromTx(tx7));
    BOOST_CHECK_EQUAL(pool.size(), 7U);
    sortedOrder.insert(sortedOrder.begin()+1, tx7.GetHash().ToString());
    CheckSort<ancestor_score>(pool, sortedOrder);

    /* after tx6 is mined, tx7 should move up in the sort */
    std::vector<CTransactionRef> vtx;
    vtx.push_back(MakeTransactionRef(tx6));
    pool.removeForBlock(vtx, 1);

    sortedOrder.erase(sortedOrder.begin()+1);
    // Ties are broken by hash
    if (tx3.GetHash() < tx6.GetHash())
        sortedOrder.pop_back();
    else
        sortedOrder.erase(sortedOrder.end()-2);
    sortedOrder.insert(sortedOrder.begin(), tx7.GetHash().ToString());
    CheckSort<ancestor_score>(pool, sortedOrder);

    // High-fee parent, low-fee child
    // tx7 -> tx8
    CMutableTransaction tx8 = CMutableTransaction();
    tx8.vin.resize(1);
    tx8.vin[0].prevout  = COutPoint(tx7.GetHash(), 0);
    tx8.vin[0].scriptSig = CScript() << OP_11;
    tx8.vout.resize(1);
    tx8.vout[0].scriptPubKey = CScript() << OP_11 << OP_EQUAL;
    tx8.vout[0].nValue = 10*COIN;

    // Check that we sort by min(feerate, ancestor_feerate):
    // set the fee so that the ancestor feerate is above tx1/5,
    // but the transaction's own feerate is lower
    pool.addUnchecked(entry.Fee(5000LL).FromTx(tx8));
    sortedOrder.insert(sortedOrder.end()-1, tx8.GetHash().ToString());
    CheckSort<ancestor_score>(pool, sortedOrder);
}


BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
{
    auto& pool = static_cast<MemPoolTest&>(*Assert(m_node.mempool));
    LOCK2(cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    CMutableTransaction tx1 = CMutableTransaction();
    tx1.vin.resize(1);
    tx1.vin[0].scriptSig = CScript() << OP_1;
    tx1.vout.resize(1);
    tx1.vout[0].scriptPubKey = CScript() << OP_1 << OP_EQUAL;
    tx1.vout[0].nValue = 10 * COIN;
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx1));

    CMutableTransaction tx2 = CMutableTransaction();
    tx2.vin.resize(1);
    tx2.vin[0].scriptSig = CScript() << OP_2;
    tx2.vout.resize(1);
    tx2.vout[0].scriptPubKey = CScript() << OP_2 << OP_EQUAL;
    tx2.vout[0].nValue = 10 * COIN;
    pool.addUnchecked(entry.Fee(5000LL).FromTx(tx2));

    pool.TrimToSize(pool.DynamicMemoryUsage()); // should do nothing
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx1.GetHash())));
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx2.GetHash())));

    pool.TrimToSize(pool.DynamicMemoryUsage() * 3 / 4); // should remove the lower-feerate transaction
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx1.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx2.GetHash())));

    pool.addUnchecked(entry.FromTx(tx2));
    CMutableTransaction tx3 = CMutableTransaction();
    tx3.vin.resize(1);
    tx3.vin[0].prevout = COutPoint(tx2.GetHash(), 0);
    tx3.vin[0].scriptSig = CScript() << OP_2;
    tx3.vout.resize(1);
    tx3.vout[0].scriptPubKey = CScript() << OP_3 << OP_EQUAL;
    tx3.vout[0].nValue = 10 * COIN;
    pool.addUnchecked(entry.Fee(20000LL).FromTx(tx3));

    pool.TrimToSize(pool.DynamicMemoryUsage() * 3 / 4); // tx3 should pay for tx2 (CPFP)
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx1.GetHash())));
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx2.GetHash())));
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx3.GetHash())));

    pool.TrimToSize(GetVirtualTransactionSize(CTransaction(tx1))); // mempool is limited to tx1's size in memory usage, so nothing fits
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx1.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx2.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx3.GetHash())));

    CFeeRate maxFeeRateRemoved(25000, GetVirtualTransactionSize(CTransaction(tx3)) + GetVirtualTransactionSize(CTransaction(tx2)));
    BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), maxFeeRateRemoved.GetFeePerK() + 1000);

    CMutableTransaction tx4 = CMutableTransaction();
    tx4.vin.resize(2);
    tx4.vin[0].prevout.SetNull();
    tx4.vin[0].scriptSig = CScript() << OP_4;
    tx4.vin[1].prevout.SetNull();
    tx4.vin[1].scriptSig = CScript() << OP_4;
    tx4.vout.resize(2);
    tx4.vout[0].scriptPubKey = CScript() << OP_4 << OP_EQUAL;
    tx4.vout[0].nValue = 10 * COIN;
    tx4.vout[1].scriptPubKey = CScript() << OP_4 << OP_EQUAL;
    tx4.vout[1].nValue = 10 * COIN;

    CMutableTransaction tx5 = CMutableTransaction();
    tx5.vin.resize(2);
    tx5.vin[0].prevout = COutPoint(tx4.GetHash(), 0);
    tx5.vin[0].scriptSig = CScript() << OP_4;
    tx5.vin[1].prevout.SetNull();
    tx5.vin[1].scriptSig = CScript() << OP_5;
    tx5.vout.resize(2);
    tx5.vout[0].scriptPubKey = CScript() << OP_5 << OP_EQUAL;
    tx5.vout[0].nValue = 10 * COIN;
    tx5.vout[1].scriptPubKey = CScript() << OP_5 << OP_EQUAL;
    tx5.vout[1].nValue = 10 * COIN;

    CMutableTransaction tx6 = CMutableTransaction();
    tx6.vin.resize(2);
    tx6.vin[0].prevout = COutPoint(tx4.GetHash(), 1);
    tx6.vin[0].scriptSig = CScript() << OP_4;
    tx6.vin[1].prevout.SetNull();
    tx6.vin[1].scriptSig = CScript() << OP_6;
    tx6.vout.resize(2);
    tx6.vout[0].scriptPubKey = CScript() << OP_6 << OP_EQUAL;
    tx6.vout[0].nValue = 10 * COIN;
    tx6.vout[1].scriptPubKey = CScript() << OP_6 << OP_EQUAL;
    tx6.vout[1].nValue = 10 * COIN;

    CMutableTransaction tx7 = CMutableTransaction();
    tx7.vin.resize(2);
    tx7.vin[0].prevout = COutPoint(tx5.GetHash(), 0);
    tx7.vin[0].scriptSig = CScript() << OP_5;
    tx7.vin[1].prevout = COutPoint(tx6.GetHash(), 0);
    tx7.vin[1].scriptSig = CScript() << OP_6;
    tx7.vout.resize(2);
    tx7.vout[0].scriptPubKey = CScript() << OP_7 << OP_EQUAL;
    tx7.vout[0].nValue = 10 * COIN;
    tx7.vout[1].scriptPubKey = CScript() << OP_7 << OP_EQUAL;
    tx7.vout[1].nValue = 10 * COIN;

    pool.addUnchecked(entry.Fee(7000LL).FromTx(tx4));
    pool.addUnchecked(entry.Fee(1000LL).FromTx(tx5));
    pool.addUnchecked(entry.Fee(1100LL).FromTx(tx6));
    pool.addUnchecked(entry.Fee(9000LL).FromTx(tx7));

    // we only require this to remove, at max, 2 txn, because it's not clear what we're really optimizing for aside from that
    pool.TrimToSize(pool.DynamicMemoryUsage() - 1);
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx4.GetHash())));
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx6.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));

    if (!pool.exists(GenTxid::Txid(tx5.GetHash())))
        pool.addUnchecked(entry.Fee(1000LL).FromTx(tx5));
    pool.addUnchecked(entry.Fee(9000LL).FromTx(tx7));

    pool.TrimToSize(pool.DynamicMemoryUsage() / 2); // should maximize mempool size by only removing 5/7
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx4.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx5.GetHash())));
    BOOST_CHECK(pool.exists(GenTxid::Txid(tx6.GetHash())));
    BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));

    pool.addUnchecked(entry.Fee(1000LL).FromTx(tx5));
    pool.addUnchecked(entry.Fee(9000LL).FromTx(tx7));

    std::vector<CTransactionRef> vtx;
    SetMockTime(42);
    SetMockTime(42 + CTxMemPool::ROLLING_FEE_HALFLIFE);
    BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), maxFeeRateRemoved.GetFeePerK() + 1000);
    // ... we should keep the same min fee until we get a block
    pool.removeForBlock(vtx, 1);
    SetMockTime(42 + 2*CTxMemPool::ROLLING_FEE_HALFLIFE);
    BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), llround((maxFeeRateRemoved.GetFeePerK() + 1000)/2.0));
    // ... then feerate should drop 1/2 each halflife

    SetMockTime(42 + 2*CTxMemPool::ROLLING_FEE_HALFLIFE + CTxMemPool::ROLLING_FEE_HALFLIFE/2);
    BOOST_CHECK_EQUAL(pool.GetMinFee(pool.DynamicMemoryUsage() * 5 / 2).GetFeePerK(), llround((maxFeeRateRemoved.GetFeePerK() + 1000)/4.0));
    // ... with a 1/2 halflife when mempool is < 1/2 its target size

    SetMockTime(42 + 2*CTxMemPool::ROLLING_FEE_HALFLIFE + CTxMemPool::ROLLING_FEE_HALFLIFE/2 + CTxMemPool::ROLLING_FEE_HALFLIFE/4);
    BOOST_CHECK_EQUAL(pool.GetMinFee(pool.DynamicMemoryUsage() * 9 / 2).GetFeePerK(), llround((maxFeeRateRemoved.GetFeePerK() + 1000)/8.0));
    // ... with a 1/4 halflife when mempool is < 1/4 its target size

    SetMockTime(42 + 7*CTxMemPool::ROLLING_FEE_HALFLIFE + CTxMemPool::ROLLING_FEE_HALFLIFE/2 + CTxMemPool::ROLLING_FEE_HALFLIFE/4);
    BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), 1000);
    // ... but feerate should never drop below 1000

    SetMockTime(42 + 8*CTxMemPool::ROLLING_FEE_HALFLIFE + CTxMemPool::ROLLING_FEE_HALFLIFE/2 + CTxMemPool::ROLLING_FEE_HALFLIFE/4);
    BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), 0);
    // ... unless it has gone all the way to 0 (after getting past 1000/2)
}

inline CTransactionRef make_tx(std::vector<CAmount>&& output_values, std::vector<CTransactionRef>&& inputs=std::vector<CTransactionRef>(), std::vector<uint32_t>&& input_indices=std::vector<uint32_t>())
{
    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 = input_indices.size() > i ? input_indices[i] : 0;
    }
    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);
}


BOOST_AUTO_TEST_CASE(MempoolAncestryTests)
{
    size_t ancestors, descendants;

    CTxMemPool& pool = *Assert(m_node.mempool);
    LOCK2(cs_main, pool.cs);
    TestMemPoolEntryHelper entry;

    /* Base transaction */
    //
    // [tx1]
    //
    CTransactionRef tx1 = make_tx(/*output_values=*/{10 * COIN});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx1));

    // Ancestors / descendants should be 1 / 1 (itself / itself)
    pool.GetTransactionAncestry(tx1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 1ULL);

    /* Child transaction */
    //
    // [tx1].0 <- [tx2]
    //
    CTransactionRef tx2 = make_tx(/*output_values=*/{495 * CENT, 5 * COIN}, /*inputs=*/{tx1});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx2));

    // Ancestors / descendants should be:
    // transaction  ancestors   descendants
    // ============ =========== ===========
    // tx1          1 (tx1)     2 (tx1,2)
    // tx2          2 (tx1,2)   2 (tx1,2)
    pool.GetTransactionAncestry(tx1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 2ULL);
    pool.GetTransactionAncestry(tx2->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 2ULL);

    /* Grand-child 1 */
    //
    // [tx1].0 <- [tx2].0 <- [tx3]
    //
    CTransactionRef tx3 = make_tx(/*output_values=*/{290 * CENT, 200 * CENT}, /*inputs=*/{tx2});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx3));

    // Ancestors / descendants should be:
    // transaction  ancestors   descendants
    // ============ =========== ===========
    // tx1          1 (tx1)     3 (tx1,2,3)
    // tx2          2 (tx1,2)   3 (tx1,2,3)
    // tx3          3 (tx1,2,3) 3 (tx1,2,3)
    pool.GetTransactionAncestry(tx1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 3ULL);
    pool.GetTransactionAncestry(tx2->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 3ULL);
    pool.GetTransactionAncestry(tx3->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 3ULL);

    /* Grand-child 2 */
    //
    // [tx1].0 <- [tx2].0 <- [tx3]
    //              |
    //              \---1 <- [tx4]
    //
    CTransactionRef tx4 = make_tx(/*output_values=*/{290 * CENT, 250 * CENT}, /*inputs=*/{tx2}, /*input_indices=*/{1});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tx4));

    // Ancestors / descendants should be:
    // transaction  ancestors   descendants
    // ============ =========== ===========
    // tx1          1 (tx1)     4 (tx1,2,3,4)
    // tx2          2 (tx1,2)   4 (tx1,2,3,4)
    // tx3          3 (tx1,2,3) 4 (tx1,2,3,4)
    // tx4          3 (tx1,2,4) 4 (tx1,2,3,4)
    pool.GetTransactionAncestry(tx1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(tx2->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(tx3->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(tx4->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);

    /* Make an alternate branch that is longer and connect it to tx3 */
    //
    // [ty1].0 <- [ty2].0 <- [ty3].0 <- [ty4].0 <- [ty5].0
    //                                              |
    // [tx1].0 <- [tx2].0 <- [tx3].0 <- [ty6] --->--/
    //              |
    //              \---1 <- [tx4]
    //
    CTransactionRef ty1, ty2, ty3, ty4, ty5;
    CTransactionRef* ty[5] = {&ty1, &ty2, &ty3, &ty4, &ty5};
    CAmount v = 5 * COIN;
    for (uint64_t i = 0; i < 5; i++) {
        CTransactionRef& tyi = *ty[i];
        tyi = make_tx(/*output_values=*/{v}, /*inputs=*/i > 0 ? std::vector<CTransactionRef>{*ty[i - 1]} : std::vector<CTransactionRef>{});
        v -= 50 * CENT;
        pool.addUnchecked(entry.Fee(10000LL).FromTx(tyi));
        pool.GetTransactionAncestry(tyi->GetHash(), ancestors, descendants);
        BOOST_CHECK_EQUAL(ancestors, i+1);
        BOOST_CHECK_EQUAL(descendants, i+1);
    }
    CTransactionRef ty6 = make_tx(/*output_values=*/{5 * COIN}, /*inputs=*/{tx3, ty5});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(ty6));

    // Ancestors / descendants should be:
    // transaction  ancestors           descendants
    // ============ =================== ===========
    // tx1          1 (tx1)             5 (tx1,2,3,4, ty6)
    // tx2          2 (tx1,2)           5 (tx1,2,3,4, ty6)
    // tx3          3 (tx1,2,3)         5 (tx1,2,3,4, ty6)
    // tx4          3 (tx1,2,4)         5 (tx1,2,3,4, ty6)
    // ty1          1 (ty1)             6 (ty1,2,3,4,5,6)
    // ty2          2 (ty1,2)           6 (ty1,2,3,4,5,6)
    // ty3          3 (ty1,2,3)         6 (ty1,2,3,4,5,6)
    // ty4          4 (y1234)           6 (ty1,2,3,4,5,6)
    // ty5          5 (y12345)          6 (ty1,2,3,4,5,6)
    // ty6          9 (tx123, ty123456) 6 (ty1,2,3,4,5,6)
    pool.GetTransactionAncestry(tx1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 5ULL);
    pool.GetTransactionAncestry(tx2->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 5ULL);
    pool.GetTransactionAncestry(tx3->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 5ULL);
    pool.GetTransactionAncestry(tx4->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 5ULL);
    pool.GetTransactionAncestry(ty1->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
    pool.GetTransactionAncestry(ty2->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
    pool.GetTransactionAncestry(ty3->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
    pool.GetTransactionAncestry(ty4->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 4ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
    pool.GetTransactionAncestry(ty5->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 5ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
    pool.GetTransactionAncestry(ty6->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 9ULL);
    BOOST_CHECK_EQUAL(descendants, 6ULL);
}

BOOST_AUTO_TEST_CASE(MempoolAncestryTestsDiamond)
{
    size_t ancestors, descendants;

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

    /* Ancestors represented more than once ("diamond") */
    //
    // [ta].0 <- [tb].0 -----<------- [td].0
    //            |                    |
    //            \---1 <- [tc].0 --<--/
    //
    CTransactionRef ta, tb, tc, td;
    ta = make_tx(/*output_values=*/{10 * COIN});
    tb = make_tx(/*output_values=*/{5 * COIN, 3 * COIN}, /*inputs=*/ {ta});
    tc = make_tx(/*output_values=*/{2 * COIN}, /*inputs=*/{tb}, /*input_indices=*/{1});
    td = make_tx(/*output_values=*/{6 * COIN}, /*inputs=*/{tb, tc}, /*input_indices=*/{0, 0});
    pool.addUnchecked(entry.Fee(10000LL).FromTx(ta));
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tb));
    pool.addUnchecked(entry.Fee(10000LL).FromTx(tc));
    pool.addUnchecked(entry.Fee(10000LL).FromTx(td));

    // Ancestors / descendants should be:
    // transaction  ancestors           descendants
    // ============ =================== ===========
    // ta           1 (ta               4 (ta,tb,tc,td)
    // tb           2 (ta,tb)           4 (ta,tb,tc,td)
    // tc           3 (ta,tb,tc)        4 (ta,tb,tc,td)
    // td           4 (ta,tb,tc,td)     4 (ta,tb,tc,td)
    pool.GetTransactionAncestry(ta->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 1ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(tb->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 2ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(tc->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 3ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
    pool.GetTransactionAncestry(td->GetHash(), ancestors, descendants);
    BOOST_CHECK_EQUAL(ancestors, 4ULL);
    BOOST_CHECK_EQUAL(descendants, 4ULL);
}

BOOST_AUTO_TEST_SUITE_END()