Function MockMempoolMinFee

src/test/util/txmempool.cpp:225–258

}

void MockMempoolMinFee(const CFeeRate& target_feerate, CTxMemPool& mempool)
{
    LOCK2(cs_main, mempool.cs);
    // Transactions in the mempool will affect the new minimum feerate.
    assert(mempool.size() == 0);
    // The target feerate cannot be too low...
    // ...otherwise the transaction's feerate will need to be negative.
    assert(target_feerate > mempool.m_opts.incremental_relay_feerate);
    // ...otherwise this is not meaningful. The feerate policy uses the maximum of both feerates.
    assert(target_feerate > mempool.m_opts.min_relay_feerate);

    // Manually create an invalid transaction. Manually set the fee in the CTxMemPoolEntry to
    // achieve the exact target feerate.
    CMutableTransaction mtx{};
    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256{123}), 0});
    mtx.vout.emplace_back(1 * COIN, GetScriptForDestination(WitnessV0ScriptHash(CScript() << OP_TRUE)));
    // Set a large size so that the fee evaluated at target_feerate (which is usually in sats/kvB) is an integer.
    // Otherwise, GetMinFee() may end up slightly different from target_feerate.
    BulkTransaction(mtx, 4000);
    const auto tx{MakeTransactionRef(mtx)};
    LockPoints lp;
    // The new mempool min feerate is equal to the removed package's feerate + incremental feerate.
    const auto tx_fee = target_feerate.GetFee(GetVirtualTransactionSize(*tx)) -
        mempool.m_opts.incremental_relay_feerate.GetFee(GetVirtualTransactionSize(*tx));
    {
        auto changeset = mempool.GetChangeSet();
        changeset->StageAddition(tx, /*fee=*/tx_fee,
                /*time=*/0, /*entry_height=*/1, /*entry_sequence=*/0,
                /*spends_coinbase=*/true, /*sigops_cost=*/1, lp);
        changeset->Apply();
    }
    mempool.TrimToSize(0);
    assert(mempool.GetMinFee() == target_feerate);
}