stakecontendercache_tests.cpp

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// Copyright (c) 2024 The Bitcoin developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <avalanche/stakecontendercache.h>
 
#include <avalanche/peermanager.h>
#include <script/script.h>
 
#include <avalanche/test/util.h>
#include <test/util/random.h>
#include <test/util/setup_common.h>
#include <util/time.h>
#include <validation.h>
 
#include <boost/test/unit_test.hpp>
 
#include <limits>
 
using namespace avalanche;
 
namespace {
struct PeerManagerFixture : public TestChain100Setup {
    PeerManagerFixture() {
        gArgs.ForceSetArg("-avaproofstakeutxoconfirmations", "1");
    }
    ~PeerManagerFixture() {
        gArgs.ClearForcedArg("-avaproofstakeutxoconfirmations");
    }
};
} // namespace
 
BOOST_FIXTURE_TEST_SUITE(stakecontendercache_tests, TestChain100Setup)
 
static void CheckWinners(StakeContenderCache &cache,
                         const BlockHash &prevblockhash,
                         std::vector<CScript> manualWinners,
                         std::vector<ProofRef> acceptedWinners,
                         std::vector<ProofRef> rejectedWinners) {
    std::vector<std::pair<ProofId, CScript>> winners;
    size_t expectedSize =
        manualWinners.size() + acceptedWinners.size() + rejectedWinners.size();
    if (expectedSize == 0) {
        BOOST_CHECK(!cache.getWinners(prevblockhash, winners));
        return;
    }
 
    BOOST_CHECK(cache.getWinners(prevblockhash, winners));
    BOOST_CHECK_EQUAL(winners.size(), expectedSize);
 
    // Manual winners are always first and in order
    for (size_t i = 0; i < manualWinners.size(); i++) {
        BOOST_CHECK(winners[i].second == manualWinners[i]);
    }
 
    // Rest of the the winners are only those determined by avalanche.
    for (auto &proof : acceptedWinners) {
        BOOST_CHECK(
            std::find_if(std::next(winners.begin(), manualWinners.size()),
                         std::next(winners.begin(), manualWinners.size() +
                                                        acceptedWinners.size()),
                         [&](std::pair<ProofId, CScript> &p) {
                             return p.first == proof->getId();
                         }) != winners.end());
    }
    for (auto &proof : rejectedWinners) {
        BOOST_CHECK(
            std::find_if(std::next(winners.begin(), manualWinners.size() +
                                                        acceptedWinners.size()),
                         winners.end(), [&](std::pair<ProofId, CScript> &p) {
                             return p.first == proof->getId();
                         }) != winners.end());
    }
 
    // Verify the winner order such that the best (lowest) reward ranked proof's
    // payout script is always before payout scripts from proofs with worse
    // (higher) reward ranks.
    double previousRank = 0;
    for (auto it = std::next(winners.begin(), manualWinners.size());
         it != std::next(winners.begin(),
                         manualWinners.size() + acceptedWinners.size());
         it++) {
        double proofRank = StakeContenderId(prevblockhash, it->first)
                               .ComputeProofRewardRank(MIN_VALID_PROOF_SCORE);
        BOOST_CHECK(previousRank < proofRank);
        previousRank = proofRank;
    }
    previousRank = 0;
    for (auto it = std::next(winners.begin(),
                             manualWinners.size() + acceptedWinners.size());
         it != winners.end(); it++) {
        double proofRank = StakeContenderId(prevblockhash, it->first)
                               .ComputeProofRewardRank(MIN_VALID_PROOF_SCORE);
        BOOST_CHECK(previousRank < proofRank);
        previousRank = proofRank;
    }
}
 
static void CheckVoteStatus(StakeContenderCache &cache,
                            const BlockHash &prevblockhash,
                            const ProofRef &proof, int expected) {
    BlockHash checkprevblockhash;
    BOOST_CHECK_EQUAL(
        cache.getVoteStatus(StakeContenderId(prevblockhash, proof->getId()),
                            checkprevblockhash),
        expected);
    if (expected != -1) {
        BOOST_CHECK_EQUAL(prevblockhash, checkprevblockhash);
    }
}
 
BOOST_AUTO_TEST_CASE(vote_status_tests) {
    Chainstate &active_chainstate = Assert(m_node.chainman)->ActiveChainstate();
    StakeContenderCache cache;
 
    CBlockIndex *pindex = active_chainstate.m_chain.Tip();
    const BlockHash &blockhash = pindex->GetBlockHash();
 
    std::vector<int> initialStatuses = {
        StakeContenderStatus::UNKNOWN, StakeContenderStatus::ACCEPTED,
        StakeContenderStatus::IN_WINNER_SET,
        StakeContenderStatus::ACCEPTED | StakeContenderStatus::IN_WINNER_SET};
    for (uint8_t initialStatus : initialStatuses) {
        auto proof = buildRandomProof(active_chainstate, MIN_VALID_PROOF_SCORE);
 
        // Unknown contender
        CheckVoteStatus(cache, blockhash, proof, -1);
 
        // Add the contender and check its vote after avalanche updates
        BOOST_CHECK(cache.add(pindex, proof, initialStatus));
        CheckVoteStatus(cache, blockhash, proof,
                        !(initialStatus & StakeContenderStatus::ACCEPTED));
 
        cache.accept(StakeContenderId(blockhash, proof->getId()));
        CheckVoteStatus(cache, blockhash, proof, 0);
 
        cache.reject(StakeContenderId(blockhash, proof->getId()));
        CheckVoteStatus(cache, blockhash, proof, 1);
 
        cache.finalize(StakeContenderId(blockhash, proof->getId()));
        CheckVoteStatus(cache, blockhash, proof, 0);
 
        // Add the proof as a manual winner. It should always be accepted.
        BOOST_CHECK(cache.setWinners(pindex, {proof->getPayoutScript()}));
        CheckVoteStatus(cache, blockhash, proof, 0);
    }
}
 
BOOST_AUTO_TEST_CASE(winners_tests) {
    Chainstate &active_chainstate = Assert(m_node.chainman)->ActiveChainstate();
    StakeContenderCache cache;
 
    std::vector<CScript> manualWinners = {
        CScript() << OP_TRUE,
        CScript() << OP_FALSE,
    };
 
    std::vector<ProofRef> proofs;
    proofs.reserve(4);
    for (int i = 0; i < 4; i++) {
        proofs.push_back(
            buildRandomProof(active_chainstate, MIN_VALID_PROOF_SCORE));
    }
 
    // Repeat these tests with multiple block hashes to ensure no unintended
    // modifications are made to other entries
    CBlockIndex *pindex = active_chainstate.m_chain.Tip();
    for (int i = 0; i < 5; i++) {
        const BlockHash &blockhash = pindex->GetBlockHash();
        CheckWinners(cache, blockhash, {}, {}, {});
 
        // Add a winner manually
        BOOST_CHECK(cache.setWinners(pindex, {manualWinners[0]}));
        CheckWinners(cache, blockhash, {manualWinners[0]}, {}, {});
 
        // Before adding contenders, check that vote status is unknown
        for (int p = 0; p < 4; p++) {
            CheckVoteStatus(cache, blockhash, proofs[p], -1);
        }
 
        // Add some contenders
        // Local winner
        BOOST_CHECK(cache.add(pindex, proofs[0],
                              StakeContenderStatus::ACCEPTED |
                                  StakeContenderStatus::IN_WINNER_SET));
        CheckVoteStatus(cache, blockhash, proofs[0], 0);
 
        // Potential winner other than the local winner
        BOOST_CHECK(
            cache.add(pindex, proofs[1], StakeContenderStatus::ACCEPTED));
        CheckVoteStatus(cache, blockhash, proofs[1], 0);
 
        // Local winner that has been rejected by avalanche so far
        BOOST_CHECK(
            cache.add(pindex, proofs[2], StakeContenderStatus::IN_WINNER_SET));
        CheckVoteStatus(cache, blockhash, proofs[2], 1);
 
        // Some other contender
        BOOST_CHECK(cache.add(pindex, proofs[3]));
        CheckVoteStatus(cache, blockhash, proofs[3], 1);
 
        // Attempting to add duplicates fails, even if status is different than
        // the successfully added entries.
        for (const auto &proof : proofs) {
            BOOST_CHECK(!cache.add(pindex, proof));
            BOOST_CHECK(
                !cache.add(pindex, proof, StakeContenderStatus::ACCEPTED));
            BOOST_CHECK(!cache.add(pindex, proof,
                                   StakeContenderStatus::ACCEPTED |
                                       StakeContenderStatus::IN_WINNER_SET));
            BOOST_CHECK(
                !cache.add(pindex, proof, StakeContenderStatus::IN_WINNER_SET));
        }
 
        CheckWinners(cache, blockhash, {manualWinners[0]}, {proofs[0]},
                     {proofs[2]});
 
        // Add another manual winner. It always comes before contenders in the
        // winner set.
        BOOST_CHECK(cache.setWinners(pindex, manualWinners));
        CheckWinners(cache, blockhash, manualWinners, {proofs[0]}, {proofs[2]});
 
        // Adding manual winners with the same payout scripts as contenders in
        // any state never causes conflicts
        std::vector<CScript> moreManualWinners = manualWinners;
        for (const auto &proof : proofs) {
            moreManualWinners.push_back(proof->getPayoutScript());
            BOOST_CHECK(cache.setWinners(pindex, moreManualWinners));
            CheckVoteStatus(cache, blockhash, proof, 0);
            CheckWinners(cache, blockhash, moreManualWinners, {proofs[0]},
                         {proofs[2]});
        }
        CheckWinners(cache, blockhash, moreManualWinners, {proofs[0]},
                     {proofs[2]});
 
        // Avalanche accepting all of the contenders does not change the winners
        // yet
        for (const auto &proof : proofs) {
            cache.accept(StakeContenderId(blockhash, proof->getId()));
        }
        CheckWinners(cache, blockhash, moreManualWinners,
                     {proofs[0], proofs[2]}, {});
 
        // Avalanche rejecting all of the contenders does not change the winners
        // yet
        for (const auto &proof : proofs) {
            cache.reject(StakeContenderId(blockhash, proof->getId()));
        }
        CheckWinners(cache, blockhash, moreManualWinners, {},
                     {proofs[0], proofs[2]});
 
        // Avalanche finalizing a contender already in the winner set makes no
        // difference
        cache.finalize(StakeContenderId(blockhash, proofs[0]->getId()));
        CheckWinners(cache, blockhash, moreManualWinners, {proofs[0]},
                     {proofs[2]});
 
        // Avalanche finalizing a contender that wasn't in the winner set before
        // makes a new winner
        cache.finalize(StakeContenderId(blockhash, proofs[1]->getId()));
        CheckWinners(cache, blockhash, moreManualWinners,
                     {proofs[0], proofs[1]}, {proofs[2]});
 
        // Avalanche invalidating a contender that was finalized has no effect
        // other than ordering.
        cache.reject(StakeContenderId(blockhash, proofs[1]->getId()));
        CheckWinners(cache, blockhash, moreManualWinners, {proofs[0]},
                     {proofs[1], proofs[2]});
 
        pindex = pindex->pprev;
    }
 
    // All contenders were added as manual winners at some point in this test,
    // so reflect that here.
    for (const auto &proof : proofs) {
        manualWinners.push_back(proof->getPayoutScript());
    }
 
    // Sanity check that past cached state was not poisoned
    pindex = active_chainstate.m_chain.Tip();
    for (int i = 0; i < 5; i++) {
        CheckWinners(cache, pindex->GetBlockHash(), manualWinners, {proofs[0]},
                     {proofs[1], proofs[2]});
        for (int p = 0; p < 4; p++) {
            CheckVoteStatus(cache, pindex->GetBlockHash(), proofs[p], 0);
        }
        pindex = pindex->pprev;
    }
}
 
BOOST_AUTO_TEST_CASE(cleanup_tests) {
    Chainstate &active_chainstate = Assert(m_node.chainman)->ActiveChainstate();
    StakeContenderCache cache;
 
    std::vector<ProofRef> proofs;
    proofs.reserve(10);
    for (int i = 0; i < 10; i++) {
        proofs.push_back(
            buildRandomProof(active_chainstate, MIN_VALID_PROOF_SCORE));
    }
 
    CBlockIndex *pindex = active_chainstate.m_chain.Tip();
    std::vector<BlockHash> blockhashes{pindex->GetBlockHash()};
    pindex = pindex->pprev;
    for (int i = 0; i < 3; i++) {
        BlockHash blockhash = pindex->GetBlockHash();
        blockhashes.push_back(blockhash);
        for (const auto &proof : proofs) {
            cache.add(pindex, proof, StakeContenderStatus::IN_WINNER_SET);
        }
        CheckWinners(cache, blockhash, {}, {}, proofs);
        pindex = pindex->pprev;
    }
 
    // Promote up to the height that we will allow cleanup of the cache. Note
    // that no entries are actually promoted so this test has fine tuned control
    // over which blocks have entries.
    pindex = active_chainstate.m_chain.Tip()->pprev->pprev->pprev;
    BOOST_CHECK_EQUAL(pindex->nHeight, 97);
    cache.promoteToBlock(pindex, [](const ProofId &proofid) { return false; });
 
    // Cleaning up nonexistant entries has no impact
    for (int height : {0, 10, 50, 90, 97}) {
        cache.cleanup(height);
        CheckWinners(cache, blockhashes[0], {}, {}, {});
        CheckWinners(cache, blockhashes[1], {}, {}, proofs);
        CheckWinners(cache, blockhashes[2], {}, {}, proofs);
        CheckWinners(cache, blockhashes[3], {}, {}, proofs);
    }
 
    // Try to cleanup oldest block in the cache, except promotion at that height
    // hasn't happened yet so cleanup has no effect.
    cache.cleanup(98);
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
    CheckWinners(cache, blockhashes[3], {}, {}, proofs);
 
    // Promote up to that height
    cache.promoteToBlock(active_chainstate.m_chain.Tip()->pprev->pprev,
                         [](const ProofId &proofid) { return false; });
 
    // Cleaning up the oldest block in the cache succeeds now
    cache.cleanup(98);
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    // Add only a local winner to the recently cleared block
    cache.setWinners(active_chainstate.m_chain.Tip()->pprev->pprev->pprev,
                     {CScript()});
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
    CheckWinners(cache, blockhashes[3], {CScript()}, {}, {});
 
    // Clean it up again
    cache.cleanup(98);
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    // Add a local winner to a block with winners already there, then clear it
    cache.setWinners(active_chainstate.m_chain.Tip()->pprev->pprev,
                     {CScript()});
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {CScript()}, {}, proofs);
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    cache.promoteToBlock(active_chainstate.m_chain.Tip()->pprev,
                         [](const ProofId &proofid) { return false; });
    cache.cleanup(99);
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, proofs);
    CheckWinners(cache, blockhashes[2], {}, {}, {});
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    // Clean up the remaining block and the cache should be empty now
    cache.promoteToBlock(active_chainstate.m_chain.Tip(),
                         [](const ProofId &proofid) { return false; });
    cache.cleanup(100);
    BOOST_CHECK(cache.isEmpty());
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, {});
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    // Cleaning up again has no effect
    cache.cleanup(100);
    BOOST_CHECK(cache.isEmpty());
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, {});
    CheckWinners(cache, blockhashes[3], {}, {}, {});
 
    // Add winners back with random states and sanity check that higher heights
    // clear the cache as we expect.
    for (int height : {102, 200, 1000, 1000000}) {
        pindex = active_chainstate.m_chain.Tip()->pprev;
        for (size_t i = 1; i < 3; i++) {
            for (const auto &proof : proofs) {
                cache.add(pindex, proof, InsecureRandBits(2));
                cache.setWinners(pindex, {CScript()});
            }
 
            // Sanity check there are some winners
            std::vector<std::pair<ProofId, CScript>> winners;
            BOOST_CHECK(cache.getWinners(blockhashes[i], winners));
            BOOST_CHECK(winners.size() >= 1);
            pindex = pindex->pprev;
        }
 
        // Cleaning up the cache at a height higher than any cache entry results
        // in an empty cache and no winners.
        cache.cleanup(height);
        BOOST_CHECK(cache.isEmpty());
        CheckWinners(cache, blockhashes[0], {}, {}, {});
        CheckWinners(cache, blockhashes[1], {}, {}, {});
        CheckWinners(cache, blockhashes[2], {}, {}, {});
        CheckWinners(cache, blockhashes[3], {}, {}, {});
    }
 
    // But note that the cache will never cleanup higher than the last promoted
    // block.
    cache.add(active_chainstate.m_chain.Tip(), proofs[0],
              StakeContenderStatus::IN_WINNER_SET);
    for (int height : {102, 200, 1000, 1000000}) {
        cache.cleanup(height);
        CheckWinners(cache, blockhashes[0], {}, {}, {proofs[0]});
        CheckWinners(cache, blockhashes[1], {}, {}, {});
        CheckWinners(cache, blockhashes[2], {}, {}, {});
        CheckWinners(cache, blockhashes[3], {}, {}, {});
    }
}
 
BOOST_FIXTURE_TEST_CASE(promote_tests, PeerManagerFixture) {
    Chainstate &active_chainstate = Assert(m_node.chainman)->ActiveChainstate();
    StakeContenderCache cache;
 
    std::vector<ProofRef> proofs;
    proofs.reserve(3);
    for (size_t i = 0; i < 3; i++) {
        proofs.push_back(
            buildRandomProof(active_chainstate, MIN_VALID_PROOF_SCORE));
    }
 
    CBlockIndex *pindex = active_chainstate.m_chain.Tip();
    const CBlockIndex *tip = pindex;
    std::vector<BlockHash> blockhashes;
    for (size_t i = 0; i < 3; i++) {
        blockhashes.push_back(pindex->GetBlockHash());
        pindex = pindex->pprev;
    }
 
    // Add one proof each to the cache for some early blocks
    for (size_t i = 0; i < 3; i++) {
        BlockHash blockhash = pindex->GetBlockHash();
        blockhashes.push_back(blockhash);
        cache.add(pindex, proofs[i], StakeContenderStatus::IN_WINNER_SET);
        CheckWinners(cache, blockhash, {}, {}, {proofs[i]});
        pindex = pindex->pprev;
    }
 
    // Attempting to cleanup the cache before promotion has occurred has no
    // effect.
    for (int height = 95; height <= 100; height++) {
        cache.cleanup(height);
        CheckWinners(cache, blockhashes[0], {}, {}, {});
        CheckWinners(cache, blockhashes[1], {}, {}, {});
        CheckWinners(cache, blockhashes[2], {}, {}, {});
        CheckWinners(cache, blockhashes[3], {}, {}, {proofs[0]});
        CheckWinners(cache, blockhashes[4], {}, {}, {proofs[1]});
        CheckWinners(cache, blockhashes[5], {}, {}, {proofs[2]});
    }
 
    // Promote contenders, but they are not winners at that block yet
    cache.promoteToBlock(tip->pprev->pprev,
                         [](const ProofId &proofid) { return true; });
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, {});
    for (auto &proof : proofs) {
        // Contenders are unknown for blocks with no cache entries
        CheckVoteStatus(cache, blockhashes[0], proof, -1);
        CheckVoteStatus(cache, blockhashes[1], proof, -1);
        // Contenders are not winners yet at the promoted block
        CheckVoteStatus(cache, blockhashes[2], proof, 1);
    }
 
    // The contenders are still winners for their respective blocks
    CheckWinners(cache, blockhashes[3], {}, {}, {proofs[0]});
    CheckWinners(cache, blockhashes[4], {}, {}, {proofs[1]});
    CheckWinners(cache, blockhashes[5], {}, {}, {proofs[2]});
 
    // Cleaning up the cache leaves most recent promoted entries alone
    cache.cleanup(98);
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, {});
    for (auto &proof : proofs) {
        // Contenders are unknown for blocks with no cache entries
        CheckVoteStatus(cache, blockhashes[0], proof, -1);
        CheckVoteStatus(cache, blockhashes[1], proof, -1);
        // Contenders at the promoted block are rejected
        CheckVoteStatus(cache, blockhashes[2], proof, 1);
    }
    CheckWinners(cache, blockhashes[3], {}, {}, {});
    CheckWinners(cache, blockhashes[4], {}, {}, {});
    CheckWinners(cache, blockhashes[5], {}, {}, {});
 
    // Finalize those proofs
    for (auto &proof : proofs) {
        cache.finalize(StakeContenderId(blockhashes[2], proof->getId()));
        // Contenders are unknown for blocks with no cache entries
        CheckVoteStatus(cache, blockhashes[0], proof, -1);
        CheckVoteStatus(cache, blockhashes[1], proof, -1);
        // Contenders at the promoted block are now accepted
        CheckVoteStatus(cache, blockhashes[2], proof, 0);
    }
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
 
    // Attempting to promote to the same block again is a no-op and statuses
    // remain unchanged.
    cache.promoteToBlock(tip->pprev->pprev,
                         [](const ProofId &proofid) { return true; });
    for (auto &proof : proofs) {
        // Contenders are unknown for blocks with no cache entries
        CheckVoteStatus(cache, blockhashes[0], proof, -1);
        CheckVoteStatus(cache, blockhashes[1], proof, -1);
        // Contenders at the promoted block are still accepted
        CheckVoteStatus(cache, blockhashes[2], proof, 0);
    }
    CheckWinners(cache, blockhashes[0], {}, {}, {});
    CheckWinners(cache, blockhashes[1], {}, {}, {});
    CheckWinners(cache, blockhashes[2], {}, {}, proofs);
 
    // Now advance the tip and invalidate a proof
    cache.promoteToBlock(tip->pprev, [&](const ProofId &proofid) {
        return proofid != proofs[2]->getId();
    });
    for (auto &proof : proofs) {
        // Contenders are unknown for blocks with no cache entries
        CheckVoteStatus(cache, blockhashes[0], proof, -1);
    }
    CheckVoteStatus(cache, blockhashes[1], proofs[0], 1);
    CheckVoteStatus(cache, blockhashes[1], proofs[1], 1);
    CheckVoteStatus(cache, blockhashes[1], proofs[2], -1);
}
 
BOOST_AUTO_TEST_CASE(pollable_contenders_tests) {
    Chainstate &active_chainstate = Assert(m_node.chainman)->ActiveChainstate();
    StakeContenderCache cache;
 
    CBlockIndex *pindex = active_chainstate.m_chain.Tip();
    const BlockHash &blockhash = pindex->GetBlockHash();
 
    const size_t maxPollable = 12;
    std::vector<StakeContenderId> contenders;
    BOOST_CHECK_EQUAL(
        cache.getPollableContenders(blockhash, maxPollable, contenders), 0);
 
    size_t numAccepted = 0;
    for (size_t c = 0; c < maxPollable * 2; c++) {
        // Add a new contender with random initial state
        auto proof = buildRandomProof(active_chainstate, MIN_VALID_PROOF_SCORE);
        BOOST_CHECK(cache.add(pindex, proof, InsecureRandBits(2)));
 
        BlockHash dummy;
        StakeContenderId contenderId(blockhash, proof->getId());
        numAccepted += cache.getVoteStatus(contenderId, dummy) == 0 ? 1 : 0;
 
        // We should never get more contenders than we can poll for in a single
        // message.
        BOOST_CHECK(cache.getPollableContenders(blockhash, maxPollable,
                                                contenders) <= maxPollable);
        BOOST_CHECK(contenders.size() <= maxPollable);
 
        double lastRank = 0;
        size_t countAccepted = 0;
        for (const auto &contender : contenders) {
            // Check the contender rank is sorted as we expect
            double rank =
                contender.ComputeProofRewardRank(MIN_VALID_PROOF_SCORE);
            BOOST_CHECK(lastRank <= rank);
            lastRank = rank;
 
            countAccepted += cache.getVoteStatus(contender, dummy) == 0 ? 1 : 0;
        }
 
        // All accepted contenders should always be returned (up to the max)
        BOOST_CHECK_EQUAL(countAccepted, std::min(numAccepted, maxPollable));
    }
}
 
BOOST_AUTO_TEST_SUITE_END()