diff --git a/src/bench/rpc_mempool.cpp b/src/bench/rpc_mempool.cpp
new file mode 100644
index 00000000000..67c827d0d33
--- /dev/null
+++ b/src/bench/rpc_mempool.cpp
@@ -0,0 +1,40 @@
+// Copyright (c) 2011-2020 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 <bench/bench.h>
+#include <rpc/blockchain.h>
+#include <txmempool.h>
+
+#include <univalue.h>
+
+
+static void AddTx(const CTransactionRef& tx, const CAmount& fee, CTxMemPool& pool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, pool.cs)
+{
+    LockPoints lp;
+    pool.addUnchecked(CTxMemPoolEntry(tx, fee, /*time=*/0, /*entry_height=*/1, /*spends_coinbase=*/false, /*sigops_cost=*/4, lp));
+}
+
+static void RpcMempool(benchmark::Bench& bench)
+{
+    CTxMemPool pool;
+    LOCK2(cs_main, pool.cs);
+
+    for (int i = 0; i < 1000; ++i) {
+        CMutableTransaction tx = CMutableTransaction();
+        tx.vin.resize(1);
+        tx.vin[0].scriptSig = CScript() << OP_1;
+        tx.vin[0].scriptWitness.stack.push_back({1});
+        tx.vout.resize(1);
+        tx.vout[0].scriptPubKey = CScript() << OP_1 << OP_EQUAL;
+        tx.vout[0].nValue = i;
+        const CTransactionRef tx_r{MakeTransactionRef(tx)};
+        AddTx(tx_r, /* fee */ i, pool);
+    }
+
+    bench.run([&] {
+        (void)MempoolToJSON(pool, /*verbose*/ true);
+    });
+}
+
+BENCHMARK(RpcMempool);
diff --git a/src/qt/test/test_main.cpp b/src/qt/test/test_main.cpp
index 3d846b4a83c..e7abfc91b37 100644
--- a/src/qt/test/test_main.cpp
+++ b/src/qt/test/test_main.cpp
@@ -66,7 +66,7 @@ int main(int argc, char *argv[])
     #if defined(WIN32)
         _putenv_s("QT_QPA_PLATFORM", "minimal");
     #else
-        setenv("QT_QPA_PLATFORM", "minimal", 0);
+        setenv("QT_QPA_PLATFORM", "minimal", 0 /* overwrite */);
     #endif
 
     // Don't remove this, it's needed to access
diff --git a/src/test/denialofservice_tests.cpp b/src/test/denialofservice_tests.cpp
new file mode 100644
index 00000000000..765663e0ef2
--- /dev/null
+++ b/src/test/denialofservice_tests.cpp
@@ -0,0 +1,432 @@
+// Copyright (c) 2011-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// Unit tests for denial-of-service detection/prevention code
+
+#include <arith_uint256.h>
+#include <banman.h>
+#include <chainparams.h>
+#include <net.h>
+#include <net_processing.h>
+#include <pubkey.h>
+#include <script/sign.h>
+#include <script/signingprovider.h>
+#include <script/standard.h>
+#include <serialize.h>
+#include <test/util/net.h>
+#include <test/util/setup_common.h>
+#include <txorphanage.h>
+#include <util/string.h>
+#include <util/system.h>
+#include <util/time.h>
+#include <validation.h>
+
+#include <array>
+#include <stdint.h>
+
+#include <boost/test/unit_test.hpp>
+
+static CService ip(uint32_t i)
+{
+    struct in_addr s;
+    s.s_addr = i;
+    return CService(CNetAddr(s), Params().GetDefaultPort());
+}
+
+static NodeId id = 0;
+
+void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds);
+
+BOOST_FIXTURE_TEST_SUITE(denialofservice_tests, TestingSetup)
+
+// Test eviction of an outbound peer whose chain never advances
+// Mock a node connection, and use mocktime to simulate a peer
+// which never sends any headers messages.  PeerLogic should
+// decide to evict that outbound peer, after the appropriate timeouts.
+// Note that we protect 4 outbound nodes from being subject to
+// this logic; this test takes advantage of that protection only
+// being applied to nodes which send headers with sufficient
+// work.
+BOOST_AUTO_TEST_CASE(outbound_slow_chain_eviction)
+{
+    const CChainParams& chainparams = Params();
+    auto connman = std::make_unique<CConnman>(0x1337, 0x1337, *m_node.addrman);
+    // Disable inactivity checks for this test to avoid interference
+    static_cast<ConnmanTestMsg*>(connman.get())->SetPeerConnectTimeout(99999);
+    auto peerLogic = PeerManager::make(chainparams, *connman, *m_node.addrman, nullptr,
+                                       *m_node.chainman, *m_node.mempool, false);
+
+    // Mock an outbound peer
+    CAddress addr1(ip(0xa0b0c001), NODE_NONE);
+    CNode dummyNode1(id++, ServiceFlags(NODE_NETWORK | NODE_WITNESS), INVALID_SOCKET, addr1, /*nKeyedNetGroupIn=*/0, /*nLocalHostNonceIn=*/0, CAddress(), /*addrNameIn=*/"", ConnectionType::OUTBOUND_FULL_RELAY, /*inbound_onion=*/false);
+    dummyNode1.SetCommonVersion(PROTOCOL_VERSION);
+
+    peerLogic->InitializeNode(&dummyNode1);
+    dummyNode1.fSuccessfullyConnected = true;
+
+    // This test requires that we have a chain with non-zero work.
+    {
+        LOCK(cs_main);
+        BOOST_CHECK(m_node.chainman->ActiveChain().Tip() != nullptr);
+        BOOST_CHECK(m_node.chainman->ActiveChain().Tip()->nChainWork > 0);
+    }
+
+    // Test starts here
+    {
+        LOCK(dummyNode1.cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(&dummyNode1)); // should result in getheaders
+    }
+    {
+        LOCK(dummyNode1.cs_vSend);
+        BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
+        dummyNode1.vSendMsg.clear();
+    }
+
+    int64_t nStartTime = GetTime();
+    // Wait 21 minutes
+    SetMockTime(nStartTime+21*60);
+    {
+        LOCK(dummyNode1.cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(&dummyNode1)); // should result in getheaders
+    }
+    {
+        LOCK(dummyNode1.cs_vSend);
+        BOOST_CHECK(dummyNode1.vSendMsg.size() > 0);
+    }
+    // Wait 3 more minutes
+    SetMockTime(nStartTime+24*60);
+    {
+        LOCK(dummyNode1.cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(&dummyNode1)); // should result in disconnect
+    }
+    BOOST_CHECK(dummyNode1.fDisconnect == true);
+
+    peerLogic->FinalizeNode(dummyNode1);
+}
+
+static void AddRandomOutboundPeer(std::vector<CNode*>& vNodes, PeerManager& peerLogic, ConnmanTestMsg& connman)
+{
+    CAddress addr(ip(g_insecure_rand_ctx.randbits(32)), NODE_NONE);
+    vNodes.emplace_back(new CNode(id++, ServiceFlags(NODE_NETWORK | NODE_WITNESS), INVALID_SOCKET, addr, /*nKeyedNetGroupIn=*/0, /*nLocalHostNonceIn=*/0, CAddress(), /*addrNameIn=*/"", ConnectionType::OUTBOUND_FULL_RELAY, /*inbound_onion=*/false));
+    CNode &node = *vNodes.back();
+    node.SetCommonVersion(PROTOCOL_VERSION);
+
+    peerLogic.InitializeNode(&node);
+    node.fSuccessfullyConnected = true;
+
+    connman.AddTestNode(node);
+}
+
+BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
+{
+    const CChainParams& chainparams = Params();
+    auto connman = std::make_unique<ConnmanTestMsg>(0x1337, 0x1337, *m_node.addrman);
+    auto peerLogic = PeerManager::make(chainparams, *connman, *m_node.addrman, nullptr,
+                                       *m_node.chainman, *m_node.mempool, false);
+
+    constexpr int max_outbound_full_relay = MAX_OUTBOUND_FULL_RELAY_CONNECTIONS;
+    CConnman::Options options;
+    options.nMaxConnections = DEFAULT_MAX_PEER_CONNECTIONS;
+    options.m_max_outbound_full_relay = max_outbound_full_relay;
+    options.nMaxFeeler = MAX_FEELER_CONNECTIONS;
+
+    connman->Init(options);
+    std::vector<CNode *> vNodes;
+
+    // Mock some outbound peers
+    for (int i = 0; i < max_outbound_full_relay; ++i) {
+        AddRandomOutboundPeer(vNodes, *peerLogic, *connman);
+    }
+
+    peerLogic->CheckForStaleTipAndEvictPeers();
+
+    // No nodes should be marked for disconnection while we have no extra peers
+    for (const CNode *node : vNodes) {
+        BOOST_CHECK(node->fDisconnect == false);
+    }
+
+    SetMockTime(GetTime() + 3 * chainparams.GetConsensus().nPowTargetSpacing + 1);
+
+    // Now tip should definitely be stale, and we should look for an extra
+    // outbound peer
+    peerLogic->CheckForStaleTipAndEvictPeers();
+    BOOST_CHECK(connman->GetTryNewOutboundPeer());
+
+    // Still no peers should be marked for disconnection
+    for (const CNode *node : vNodes) {
+        BOOST_CHECK(node->fDisconnect == false);
+    }
+
+    // If we add one more peer, something should get marked for eviction
+    // on the next check (since we're mocking the time to be in the future, the
+    // required time connected check should be satisfied).
+    AddRandomOutboundPeer(vNodes, *peerLogic, *connman);
+
+    peerLogic->CheckForStaleTipAndEvictPeers();
+    for (int i = 0; i < max_outbound_full_relay; ++i) {
+        BOOST_CHECK(vNodes[i]->fDisconnect == false);
+    }
+    // Last added node should get marked for eviction
+    BOOST_CHECK(vNodes.back()->fDisconnect == true);
+
+    vNodes.back()->fDisconnect = false;
+
+    // Update the last announced block time for the last
+    // peer, and check that the next newest node gets evicted.
+    UpdateLastBlockAnnounceTime(vNodes.back()->GetId(), GetTime());
+
+    peerLogic->CheckForStaleTipAndEvictPeers();
+    for (int i = 0; i < max_outbound_full_relay - 1; ++i) {
+        BOOST_CHECK(vNodes[i]->fDisconnect == false);
+    }
+    BOOST_CHECK(vNodes[max_outbound_full_relay-1]->fDisconnect == true);
+    BOOST_CHECK(vNodes.back()->fDisconnect == false);
+
+    for (const CNode *node : vNodes) {
+        peerLogic->FinalizeNode(*node);
+    }
+
+    connman->ClearTestNodes();
+}
+
+BOOST_AUTO_TEST_CASE(peer_discouragement)
+{
+    const CChainParams& chainparams = Params();
+    auto banman = std::make_unique<BanMan>(m_args.GetDataDirBase() / "banlist", nullptr, DEFAULT_MISBEHAVING_BANTIME);
+    auto connman = std::make_unique<ConnmanTestMsg>(0x1337, 0x1337, *m_node.addrman);
+    auto peerLogic = PeerManager::make(chainparams, *connman, *m_node.addrman, banman.get(),
+                                       *m_node.chainman, *m_node.mempool, false);
+
+    CNetAddr tor_netaddr;
+    BOOST_REQUIRE(
+        tor_netaddr.SetSpecial("pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd.onion"));
+    const CService tor_service{tor_netaddr, Params().GetDefaultPort()};
+
+    const std::array<CAddress, 3> addr{CAddress{ip(0xa0b0c001), NODE_NONE},
+                                       CAddress{ip(0xa0b0c002), NODE_NONE},
+                                       CAddress{tor_service, NODE_NONE}};
+
+    const CNetAddr other_addr{ip(0xa0b0ff01)}; // Not any of addr[].
+
+    std::array<CNode*, 3> nodes;
+
+    banman->ClearBanned();
+    nodes[0] = new CNode{id++, NODE_NETWORK, INVALID_SOCKET, addr[0], /*nKeyedNetGroupIn=*/0,
+                         /*nLocalHostNonceIn */ 0, CAddress(), /*addrNameIn=*/"",
+                         ConnectionType::INBOUND, /*inbound_onion=*/false};
+    nodes[0]->SetCommonVersion(PROTOCOL_VERSION);
+    peerLogic->InitializeNode(nodes[0]);
+    nodes[0]->fSuccessfullyConnected = true;
+    connman->AddTestNode(*nodes[0]);
+    peerLogic->Misbehaving(nodes[0]->GetId(), DISCOURAGEMENT_THRESHOLD, /* message */ ""); // Should be discouraged
+    {
+        LOCK(nodes[0]->cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(nodes[0]));
+    }
+    BOOST_CHECK(banman->IsDiscouraged(addr[0]));
+    BOOST_CHECK(nodes[0]->fDisconnect);
+    BOOST_CHECK(!banman->IsDiscouraged(other_addr)); // Different address, not discouraged
+
+    nodes[1] = new CNode{id++, NODE_NETWORK, INVALID_SOCKET, addr[1], /*nKeyedNetGroupIn=*/1,
+                         /*nLocalHostNonceIn */ 1, CAddress(), /*addrNameIn=*/"",
+                         ConnectionType::INBOUND, /*inbound_onion=*/false};
+    nodes[1]->SetCommonVersion(PROTOCOL_VERSION);
+    peerLogic->InitializeNode(nodes[1]);
+    nodes[1]->fSuccessfullyConnected = true;
+    connman->AddTestNode(*nodes[1]);
+    peerLogic->Misbehaving(nodes[1]->GetId(), DISCOURAGEMENT_THRESHOLD - 1, /* message */ "");
+    {
+        LOCK(nodes[1]->cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(nodes[1]));
+    }
+    // [0] is still discouraged/disconnected.
+    BOOST_CHECK(banman->IsDiscouraged(addr[0]));
+    BOOST_CHECK(nodes[0]->fDisconnect);
+    // [1] is not discouraged/disconnected yet.
+    BOOST_CHECK(!banman->IsDiscouraged(addr[1]));
+    BOOST_CHECK(!nodes[1]->fDisconnect);
+    peerLogic->Misbehaving(nodes[1]->GetId(), 1, /* message */ ""); // [1] reaches discouragement threshold
+    {
+        LOCK(nodes[1]->cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(nodes[1]));
+    }
+    // Expect both [0] and [1] to be discouraged/disconnected now.
+    BOOST_CHECK(banman->IsDiscouraged(addr[0]));
+    BOOST_CHECK(nodes[0]->fDisconnect);
+    BOOST_CHECK(banman->IsDiscouraged(addr[1]));
+    BOOST_CHECK(nodes[1]->fDisconnect);
+
+    // Make sure non-IP peers are discouraged and disconnected properly.
+
+    nodes[2] = new CNode{id++, NODE_NETWORK, INVALID_SOCKET, addr[2], /*nKeyedNetGroupIn=*/1,
+                         /*nLocalHostNonceIn */ 1, CAddress(), /*addrNameIn=*/"",
+                         ConnectionType::OUTBOUND_FULL_RELAY, /*inbound_onion=*/false};
+    nodes[2]->SetCommonVersion(PROTOCOL_VERSION);
+    peerLogic->InitializeNode(nodes[2]);
+    nodes[2]->fSuccessfullyConnected = true;
+    connman->AddTestNode(*nodes[2]);
+    peerLogic->Misbehaving(nodes[2]->GetId(), DISCOURAGEMENT_THRESHOLD, /* message */ "");
+    {
+        LOCK(nodes[2]->cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(nodes[2]));
+    }
+    BOOST_CHECK(banman->IsDiscouraged(addr[0]));
+    BOOST_CHECK(banman->IsDiscouraged(addr[1]));
+    BOOST_CHECK(banman->IsDiscouraged(addr[2]));
+    BOOST_CHECK(nodes[0]->fDisconnect);
+    BOOST_CHECK(nodes[1]->fDisconnect);
+    BOOST_CHECK(nodes[2]->fDisconnect);
+
+    for (CNode* node : nodes) {
+        peerLogic->FinalizeNode(*node);
+    }
+    connman->ClearTestNodes();
+}
+
+BOOST_AUTO_TEST_CASE(DoS_bantime)
+{
+    const CChainParams& chainparams = Params();
+    auto banman = std::make_unique<BanMan>(m_args.GetDataDirBase() / "banlist", nullptr, DEFAULT_MISBEHAVING_BANTIME);
+    auto connman = std::make_unique<CConnman>(0x1337, 0x1337, *m_node.addrman);
+    auto peerLogic = PeerManager::make(chainparams, *connman, *m_node.addrman, banman.get(),
+                                       *m_node.chainman, *m_node.mempool, false);
+
+    banman->ClearBanned();
+    int64_t nStartTime = GetTime();
+    SetMockTime(nStartTime); // Overrides future calls to GetTime()
+
+    CAddress addr(ip(0xa0b0c001), NODE_NONE);
+    CNode dummyNode(id++, NODE_NETWORK, INVALID_SOCKET, addr, /*nKeyedNetGroupIn=*/4, /*nLocalHostNonceIn=*/4, CAddress(), /*addrNameIn=*/"", ConnectionType::INBOUND, /*inbound_onion=*/false);
+    dummyNode.SetCommonVersion(PROTOCOL_VERSION);
+    peerLogic->InitializeNode(&dummyNode);
+    dummyNode.fSuccessfullyConnected = true;
+
+    peerLogic->Misbehaving(dummyNode.GetId(), DISCOURAGEMENT_THRESHOLD, /* message */ "");
+    {
+        LOCK(dummyNode.cs_sendProcessing);
+        BOOST_CHECK(peerLogic->SendMessages(&dummyNode));
+    }
+    BOOST_CHECK(banman->IsDiscouraged(addr));
+
+    peerLogic->FinalizeNode(dummyNode);
+}
+
+class TxOrphanageTest : public TxOrphanage
+{
+public:
+    inline size_t CountOrphans() const EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
+    {
+        return m_orphans.size();
+    }
+
+    CTransactionRef RandomOrphan() EXCLUSIVE_LOCKS_REQUIRED(g_cs_orphans)
+    {
+        std::map<uint256, OrphanTx>::iterator it;
+        it = m_orphans.lower_bound(InsecureRand256());
+        if (it == m_orphans.end())
+            it = m_orphans.begin();
+        return it->second.tx;
+    }
+};
+
+static void MakeNewKeyWithFastRandomContext(CKey& key)
+{
+    std::vector<unsigned char> keydata;
+    keydata = g_insecure_rand_ctx.randbytes(32);
+    key.Set(keydata.data(), keydata.data() + keydata.size(), /*fCompressedIn*/ true);
+    assert(key.IsValid());
+}
+
+BOOST_AUTO_TEST_CASE(DoS_mapOrphans)
+{
+    // This test had non-deterministic coverage due to
+    // randomly selected seeds.
+    // This seed is chosen so that all branches of the function
+    // ecdsa_signature_parse_der_lax are executed during this test.
+    // Specifically branches that run only when an ECDSA
+    // signature's R and S values have leading zeros.
+    g_insecure_rand_ctx = FastRandomContext(ArithToUint256(arith_uint256(33)));
+
+    TxOrphanageTest orphanage;
+    CKey key;
+    MakeNewKeyWithFastRandomContext(key);
+    FillableSigningProvider keystore;
+    BOOST_CHECK(keystore.AddKey(key));
+
+    LOCK(g_cs_orphans);
+
+    // 50 orphan transactions:
+    for (int i = 0; i < 50; i++)
+    {
+        CMutableTransaction tx;
+        tx.vin.resize(1);
+        tx.vin[0].prevout.n = 0;
+        tx.vin[0].prevout.hash = InsecureRand256();
+        tx.vin[0].scriptSig << OP_1;
+        tx.vout.resize(1);
+        tx.vout[0].nValue = 1*CENT;
+        tx.vout[0].scriptPubKey = GetScriptForDestination(PKHash(key.GetPubKey()));
+
+        orphanage.AddTx(MakeTransactionRef(tx), i);
+    }
+
+    // ... and 50 that depend on other orphans:
+    for (int i = 0; i < 50; i++)
+    {
+        CTransactionRef txPrev = orphanage.RandomOrphan();
+
+        CMutableTransaction tx;
+        tx.vin.resize(1);
+        tx.vin[0].prevout.n = 0;
+        tx.vin[0].prevout.hash = txPrev->GetHash();
+        tx.vout.resize(1);
+        tx.vout[0].nValue = 1*CENT;
+        tx.vout[0].scriptPubKey = GetScriptForDestination(PKHash(key.GetPubKey()));
+        BOOST_CHECK(SignSignature(keystore, *txPrev, tx, 0, SIGHASH_ALL));
+
+        orphanage.AddTx(MakeTransactionRef(tx), i);
+    }
+
+    // This really-big orphan should be ignored:
+    for (int i = 0; i < 10; i++)
+    {
+        CTransactionRef txPrev = orphanage.RandomOrphan();
+
+        CMutableTransaction tx;
+        tx.vout.resize(1);
+        tx.vout[0].nValue = 1*CENT;
+        tx.vout[0].scriptPubKey = GetScriptForDestination(PKHash(key.GetPubKey()));
+        tx.vin.resize(2777);
+        for (unsigned int j = 0; j < tx.vin.size(); j++)
+        {
+            tx.vin[j].prevout.n = j;
+            tx.vin[j].prevout.hash = txPrev->GetHash();
+        }
+        BOOST_CHECK(SignSignature(keystore, *txPrev, tx, 0, SIGHASH_ALL));
+        // Re-use same signature for other inputs
+        // (they don't have to be valid for this test)
+        for (unsigned int j = 1; j < tx.vin.size(); j++)
+            tx.vin[j].scriptSig = tx.vin[0].scriptSig;
+
+        BOOST_CHECK(!orphanage.AddTx(MakeTransactionRef(tx), i));
+    }
+
+    // Test EraseOrphansFor:
+    for (NodeId i = 0; i < 3; i++)
+    {
+        size_t sizeBefore = orphanage.CountOrphans();
+        orphanage.EraseForPeer(i);
+        BOOST_CHECK(orphanage.CountOrphans() < sizeBefore);
+    }
+
+    // Test LimitOrphanTxSize() function:
+    orphanage.LimitOrphans(40);
+    BOOST_CHECK(orphanage.CountOrphans() <= 40);
+    orphanage.LimitOrphans(10);
+    BOOST_CHECK(orphanage.CountOrphans() <= 10);
+    orphanage.LimitOrphans(0);
+    BOOST_CHECK(orphanage.CountOrphans() == 0);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/fuzz/tx_pool.cpp b/src/test/fuzz/tx_pool.cpp
new file mode 100644
index 00000000000..752e882608d
--- /dev/null
+++ b/src/test/fuzz/tx_pool.cpp
@@ -0,0 +1,341 @@
+// Copyright (c) 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 <consensus/validation.h>
+#include <miner.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+#include <test/util/mining.h>
+#include <test/util/script.h>
+#include <test/util/setup_common.h>
+#include <util/rbf.h>
+#include <validation.h>
+#include <validationinterface.h>
+
+namespace {
+
+const TestingSetup* g_setup;
+std::vector<COutPoint> g_outpoints_coinbase_init_mature;
+std::vector<COutPoint> g_outpoints_coinbase_init_immature;
+
+struct MockedTxPool : public CTxMemPool {
+    void RollingFeeUpdate() EXCLUSIVE_LOCKS_REQUIRED(!cs)
+    {
+        LOCK(cs);
+        lastRollingFeeUpdate = GetTime();
+        blockSinceLastRollingFeeBump = true;
+    }
+};
+
+void initialize_tx_pool()
+{
+    static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>();
+    g_setup = testing_setup.get();
+
+    for (int i = 0; i < 2 * COINBASE_MATURITY; ++i) {
+        CTxIn in = MineBlock(g_setup->m_node, P2WSH_OP_TRUE);
+        // Remember the txids to avoid expensive disk access later on
+        auto& outpoints = i < COINBASE_MATURITY ?
+                              g_outpoints_coinbase_init_mature :
+                              g_outpoints_coinbase_init_immature;
+        outpoints.push_back(in.prevout);
+    }
+    SyncWithValidationInterfaceQueue();
+}
+
+struct TransactionsDelta final : public CValidationInterface {
+    std::set<CTransactionRef>& m_removed;
+    std::set<CTransactionRef>& m_added;
+
+    explicit TransactionsDelta(std::set<CTransactionRef>& r, std::set<CTransactionRef>& a)
+        : m_removed{r}, m_added{a} {}
+
+    void TransactionAddedToMempool(const CTransactionRef& tx, uint64_t /* mempool_sequence */) override
+    {
+        Assert(m_added.insert(tx).second);
+    }
+
+    void TransactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason, uint64_t /* mempool_sequence */) override
+    {
+        Assert(m_removed.insert(tx).second);
+    }
+};
+
+void SetMempoolConstraints(ArgsManager& args, FuzzedDataProvider& fuzzed_data_provider)
+{
+    args.ForceSetArg("-limitancestorcount",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 50)));
+    args.ForceSetArg("-limitancestorsize",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 202)));
+    args.ForceSetArg("-limitdescendantcount",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 50)));
+    args.ForceSetArg("-limitdescendantsize",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 202)));
+    args.ForceSetArg("-maxmempool",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 200)));
+    args.ForceSetArg("-mempoolexpiry",
+                     ToString(fuzzed_data_provider.ConsumeIntegralInRange<unsigned>(0, 999)));
+}
+
+void Finish(FuzzedDataProvider& fuzzed_data_provider, MockedTxPool& tx_pool, CChainState& chainstate)
+{
+    WITH_LOCK(::cs_main, tx_pool.check(chainstate.CoinsTip(), chainstate.m_chain.Height() + 1));
+    {
+        BlockAssembler::Options options;
+        options.nBlockMaxWeight = fuzzed_data_provider.ConsumeIntegralInRange(0U, MAX_BLOCK_WEIGHT);
+        options.blockMinFeeRate = CFeeRate{ConsumeMoney(fuzzed_data_provider, /* max */ COIN)};
+        auto assembler = BlockAssembler{chainstate, *static_cast<CTxMemPool*>(&tx_pool), ::Params(), options};
+        auto block_template = assembler.CreateNewBlock(CScript{} << OP_TRUE);
+        Assert(block_template->block.vtx.size() >= 1);
+    }
+    const auto info_all = tx_pool.infoAll();
+    if (!info_all.empty()) {
+        const auto& tx_to_remove = *PickValue(fuzzed_data_provider, info_all).tx;
+        WITH_LOCK(tx_pool.cs, tx_pool.removeRecursive(tx_to_remove, MemPoolRemovalReason::BLOCK /* dummy */));
+        std::vector<uint256> all_txids;
+        tx_pool.queryHashes(all_txids);
+        assert(all_txids.size() < info_all.size());
+        WITH_LOCK(::cs_main, tx_pool.check(chainstate.CoinsTip(), chainstate.m_chain.Height() + 1));
+    }
+    SyncWithValidationInterfaceQueue();
+}
+
+void MockTime(FuzzedDataProvider& fuzzed_data_provider, const CChainState& chainstate)
+{
+    const auto time = ConsumeTime(fuzzed_data_provider,
+                                  chainstate.m_chain.Tip()->GetMedianTimePast() + 1,
+                                  std::numeric_limits<decltype(chainstate.m_chain.Tip()->nTime)>::max());
+    SetMockTime(time);
+}
+
+FUZZ_TARGET_INIT(tx_pool_standard, initialize_tx_pool)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    const auto& node = g_setup->m_node;
+    auto& chainstate = node.chainman->ActiveChainstate();
+
+    MockTime(fuzzed_data_provider, chainstate);
+    SetMempoolConstraints(*node.args, fuzzed_data_provider);
+
+    // All RBF-spendable outpoints
+    std::set<COutPoint> outpoints_rbf;
+    // All outpoints counting toward the total supply (subset of outpoints_rbf)
+    std::set<COutPoint> outpoints_supply;
+    for (const auto& outpoint : g_outpoints_coinbase_init_mature) {
+        Assert(outpoints_supply.insert(outpoint).second);
+    }
+    outpoints_rbf = outpoints_supply;
+
+    // The sum of the values of all spendable outpoints
+    constexpr CAmount SUPPLY_TOTAL{COINBASE_MATURITY * 50 * COIN};
+
+    CTxMemPool tx_pool_{/* estimator */ nullptr, /* check_ratio */ 1};
+    MockedTxPool& tx_pool = *static_cast<MockedTxPool*>(&tx_pool_);
+
+    // Helper to query an amount
+    const CCoinsViewMemPool amount_view{WITH_LOCK(::cs_main, return &chainstate.CoinsTip()), tx_pool};
+    const auto GetAmount = [&](const COutPoint& outpoint) {
+        Coin c;
+        Assert(amount_view.GetCoin(outpoint, c));
+        return c.out.nValue;
+    };
+
+    LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 300)
+    {
+        {
+            // Total supply is the mempool fee + all outpoints
+            CAmount supply_now{WITH_LOCK(tx_pool.cs, return tx_pool.GetTotalFee())};
+            for (const auto& op : outpoints_supply) {
+                supply_now += GetAmount(op);
+            }
+            Assert(supply_now == SUPPLY_TOTAL);
+        }
+        Assert(!outpoints_supply.empty());
+
+        // Create transaction to add to the mempool
+        const CTransactionRef tx = [&] {
+            CMutableTransaction tx_mut;
+            tx_mut.nVersion = CTransaction::CURRENT_VERSION;
+            tx_mut.nLockTime = fuzzed_data_provider.ConsumeBool() ? 0 : fuzzed_data_provider.ConsumeIntegral<uint32_t>();
+            const auto num_in = fuzzed_data_provider.ConsumeIntegralInRange<int>(1, outpoints_rbf.size());
+            const auto num_out = fuzzed_data_provider.ConsumeIntegralInRange<int>(1, outpoints_rbf.size() * 2);
+
+            CAmount amount_in{0};
+            for (int i = 0; i < num_in; ++i) {
+                // Pop random outpoint
+                auto pop = outpoints_rbf.begin();
+                std::advance(pop, fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, outpoints_rbf.size() - 1));
+                const auto outpoint = *pop;
+                outpoints_rbf.erase(pop);
+                amount_in += GetAmount(outpoint);
+
+                // Create input
+                const auto sequence = ConsumeSequence(fuzzed_data_provider);
+                const auto script_sig = CScript{};
+                const auto script_wit_stack = std::vector<std::vector<uint8_t>>{WITNESS_STACK_ELEM_OP_TRUE};
+                CTxIn in;
+                in.prevout = outpoint;
+                in.nSequence = sequence;
+                in.scriptSig = script_sig;
+                in.scriptWitness.stack = script_wit_stack;
+
+                tx_mut.vin.push_back(in);
+            }
+            const auto amount_fee = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-1000, amount_in);
+            const auto amount_out = (amount_in - amount_fee) / num_out;
+            for (int i = 0; i < num_out; ++i) {
+                tx_mut.vout.emplace_back(amount_out, P2WSH_OP_TRUE);
+            }
+            const auto tx = MakeTransactionRef(tx_mut);
+            // Restore previously removed outpoints
+            for (const auto& in : tx->vin) {
+                Assert(outpoints_rbf.insert(in.prevout).second);
+            }
+            return tx;
+        }();
+
+        if (fuzzed_data_provider.ConsumeBool()) {
+            MockTime(fuzzed_data_provider, chainstate);
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            SetMempoolConstraints(*node.args, fuzzed_data_provider);
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            tx_pool.RollingFeeUpdate();
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            const auto& txid = fuzzed_data_provider.ConsumeBool() ?
+                                   tx->GetHash() :
+                                   PickValue(fuzzed_data_provider, outpoints_rbf).hash;
+            const auto delta = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-50 * COIN, +50 * COIN);
+            tx_pool.PrioritiseTransaction(txid, delta);
+        }
+
+        // Remember all removed and added transactions
+        std::set<CTransactionRef> removed;
+        std::set<CTransactionRef> added;
+        auto txr = std::make_shared<TransactionsDelta>(removed, added);
+        RegisterSharedValidationInterface(txr);
+        const bool bypass_limits = fuzzed_data_provider.ConsumeBool();
+        ::fRequireStandard = fuzzed_data_provider.ConsumeBool();
+
+        // Make sure ProcessNewPackage on one transaction works and always fully validates the transaction.
+        // The result is not guaranteed to be the same as what is returned by ATMP.
+        const auto result_package = WITH_LOCK(::cs_main,
+                                    return ProcessNewPackage(node.chainman->ActiveChainstate(), tx_pool, {tx}, true));
+        auto it = result_package.m_tx_results.find(tx->GetWitnessHash());
+        Assert(it != result_package.m_tx_results.end());
+        Assert(it->second.m_result_type == MempoolAcceptResult::ResultType::VALID ||
+               it->second.m_result_type == MempoolAcceptResult::ResultType::INVALID);
+
+        const auto res = WITH_LOCK(::cs_main, return AcceptToMemoryPool(chainstate, tx_pool, tx, bypass_limits));
+        const bool accepted = res.m_result_type == MempoolAcceptResult::ResultType::VALID;
+        SyncWithValidationInterfaceQueue();
+        UnregisterSharedValidationInterface(txr);
+
+        Assert(accepted != added.empty());
+        Assert(accepted == res.m_state.IsValid());
+        Assert(accepted != res.m_state.IsInvalid());
+        if (accepted) {
+            Assert(added.size() == 1); // For now, no package acceptance
+            Assert(tx == *added.begin());
+        } else {
+            // Do not consider rejected transaction removed
+            removed.erase(tx);
+        }
+
+        // Helper to insert spent and created outpoints of a tx into collections
+        using Sets = std::vector<std::reference_wrapper<std::set<COutPoint>>>;
+        const auto insert_tx = [](Sets created_by_tx, Sets consumed_by_tx, const auto& tx) {
+            for (size_t i{0}; i < tx.vout.size(); ++i) {
+                for (auto& set : created_by_tx) {
+                    Assert(set.get().emplace(tx.GetHash(), i).second);
+                }
+            }
+            for (const auto& in : tx.vin) {
+                for (auto& set : consumed_by_tx) {
+                    Assert(set.get().insert(in.prevout).second);
+                }
+            }
+        };
+        // Add created outpoints, remove spent outpoints
+        {
+            // Outpoints that no longer exist at all
+            std::set<COutPoint> consumed_erased;
+            // Outpoints that no longer count toward the total supply
+            std::set<COutPoint> consumed_supply;
+            for (const auto& removed_tx : removed) {
+                insert_tx(/* created_by_tx */ {consumed_erased}, /* consumed_by_tx */ {outpoints_supply}, /* tx */ *removed_tx);
+            }
+            for (const auto& added_tx : added) {
+                insert_tx(/* created_by_tx */ {outpoints_supply, outpoints_rbf}, /* consumed_by_tx */ {consumed_supply}, /* tx */ *added_tx);
+            }
+            for (const auto& p : consumed_erased) {
+                Assert(outpoints_supply.erase(p) == 1);
+                Assert(outpoints_rbf.erase(p) == 1);
+            }
+            for (const auto& p : consumed_supply) {
+                Assert(outpoints_supply.erase(p) == 1);
+            }
+        }
+    }
+    Finish(fuzzed_data_provider, tx_pool, chainstate);
+}
+
+FUZZ_TARGET_INIT(tx_pool, initialize_tx_pool)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    const auto& node = g_setup->m_node;
+    auto& chainstate = node.chainman->ActiveChainstate();
+
+    MockTime(fuzzed_data_provider, chainstate);
+    SetMempoolConstraints(*node.args, fuzzed_data_provider);
+
+    std::vector<uint256> txids;
+    for (const auto& outpoint : g_outpoints_coinbase_init_mature) {
+        txids.push_back(outpoint.hash);
+    }
+    for (int i{0}; i <= 3; ++i) {
+        // Add some immature and non-existent outpoints
+        txids.push_back(g_outpoints_coinbase_init_immature.at(i).hash);
+        txids.push_back(ConsumeUInt256(fuzzed_data_provider));
+    }
+
+    CTxMemPool tx_pool_{/* estimator */ nullptr, /* check_ratio */ 1};
+    MockedTxPool& tx_pool = *static_cast<MockedTxPool*>(&tx_pool_);
+
+    LIMITED_WHILE(fuzzed_data_provider.ConsumeBool(), 300)
+    {
+        const auto mut_tx = ConsumeTransaction(fuzzed_data_provider, txids);
+
+        if (fuzzed_data_provider.ConsumeBool()) {
+            MockTime(fuzzed_data_provider, chainstate);
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            SetMempoolConstraints(*node.args, fuzzed_data_provider);
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            tx_pool.RollingFeeUpdate();
+        }
+        if (fuzzed_data_provider.ConsumeBool()) {
+            const auto& txid = fuzzed_data_provider.ConsumeBool() ?
+                                   mut_tx.GetHash() :
+                                   PickValue(fuzzed_data_provider, txids);
+            const auto delta = fuzzed_data_provider.ConsumeIntegralInRange<CAmount>(-50 * COIN, +50 * COIN);
+            tx_pool.PrioritiseTransaction(txid, delta);
+        }
+
+        const auto tx = MakeTransactionRef(mut_tx);
+        const bool bypass_limits = fuzzed_data_provider.ConsumeBool();
+        ::fRequireStandard = fuzzed_data_provider.ConsumeBool();
+        const auto res = WITH_LOCK(::cs_main, return AcceptToMemoryPool(node.chainman->ActiveChainstate(), tx_pool, tx, bypass_limits));
+        const bool accepted = res.m_result_type == MempoolAcceptResult::ResultType::VALID;
+        if (accepted) {
+            txids.push_back(tx->GetHash());
+        }
+    }
+    Finish(fuzzed_data_provider, tx_pool, chainstate);
+}
+} // namespace
diff --git a/src/test/txpackage_tests.cpp b/src/test/txpackage_tests.cpp
new file mode 100644
index 00000000000..8d92bee2216
--- /dev/null
+++ b/src/test/txpackage_tests.cpp
@@ -0,0 +1,117 @@
+// Copyright (c) 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 <consensus/validation.h>
+#include <key_io.h>
+#include <policy/packages.h>
+#include <policy/policy.h>
+#include <primitives/transaction.h>
+#include <script/script.h>
+#include <script/standard.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE(txpackage_tests)
+
+// Create placeholder transactions that have no meaning.
+inline CTransactionRef create_placeholder_tx(size_t num_inputs, size_t num_outputs)
+{
+    CMutableTransaction mtx = CMutableTransaction();
+    mtx.vin.resize(num_inputs);
+    mtx.vout.resize(num_outputs);
+    auto random_script = CScript() << ToByteVector(InsecureRand256()) << ToByteVector(InsecureRand256());
+    for (size_t i{0}; i < num_inputs; ++i) {
+        mtx.vin[i].prevout.hash = InsecureRand256();
+        mtx.vin[i].prevout.n = 0;
+        mtx.vin[i].scriptSig = random_script;
+    }
+    for (size_t o{0}; o < num_outputs; ++o) {
+        mtx.vout[o].nValue = 1 * CENT;
+        mtx.vout[o].scriptPubKey = random_script;
+    }
+    return MakeTransactionRef(mtx);
+}
+
+BOOST_FIXTURE_TEST_CASE(package_sanitization_tests, TestChain100Setup)
+{
+    // Packages can't have more than 25 transactions.
+    Package package_too_many;
+    package_too_many.reserve(MAX_PACKAGE_COUNT + 1);
+    for (size_t i{0}; i < MAX_PACKAGE_COUNT + 1; ++i) {
+        package_too_many.emplace_back(create_placeholder_tx(1, 1));
+    }
+    PackageValidationState state_too_many;
+    BOOST_CHECK(!CheckPackage(package_too_many, state_too_many));
+    BOOST_CHECK_EQUAL(state_too_many.GetResult(), PackageValidationResult::PCKG_POLICY);
+    BOOST_CHECK_EQUAL(state_too_many.GetRejectReason(), "package-too-many-transactions");
+
+    // Packages can't have a total size of more than 101KvB.
+    CTransactionRef large_ptx = create_placeholder_tx(150, 150);
+    Package package_too_large;
+    auto size_large = GetVirtualTransactionSize(*large_ptx);
+    size_t total_size{0};
+    while (total_size <= MAX_PACKAGE_SIZE * 1000) {
+        package_too_large.push_back(large_ptx);
+        total_size += size_large;
+    }
+    BOOST_CHECK(package_too_large.size() <= MAX_PACKAGE_COUNT);
+    PackageValidationState state_too_large;
+    BOOST_CHECK(!CheckPackage(package_too_large, state_too_large));
+    BOOST_CHECK_EQUAL(state_too_large.GetResult(), PackageValidationResult::PCKG_POLICY);
+    BOOST_CHECK_EQUAL(state_too_large.GetRejectReason(), "package-too-large");
+}
+
+BOOST_FIXTURE_TEST_CASE(package_validation_tests, TestChain100Setup)
+{
+    LOCK(cs_main);
+    unsigned int initialPoolSize = m_node.mempool->size();
+
+    // Parent and Child Package
+    CKey parent_key;
+    parent_key.MakeNewKey(true);
+    CScript parent_locking_script = GetScriptForDestination(PKHash(parent_key.GetPubKey()));
+    auto mtx_parent = CreateValidMempoolTransaction(/*input_transaction=*/ m_coinbase_txns[0], /*input_vout=*/0,
+                                                    /*input_height=*/ 0, /*input_signing_key=*/coinbaseKey,
+                                                    /*output_destination=*/ parent_locking_script,
+                                                    /*output_amount=*/ CAmount(49 * COIN), /*submit=*/false);
+    CTransactionRef tx_parent = MakeTransactionRef(mtx_parent);
+
+    CKey child_key;
+    child_key.MakeNewKey(true);
+    CScript child_locking_script = GetScriptForDestination(PKHash(child_key.GetPubKey()));
+    auto mtx_child = CreateValidMempoolTransaction(/*input_transaction=*/ tx_parent, /*input_vout=*/0,
+                                                   /*input_height=*/ 101, /*input_signing_key=*/parent_key,
+                                                   /*output_destination */ child_locking_script,
+                                                   /*output_amount=*/ CAmount(48 * COIN), /*submit=*/false);
+    CTransactionRef tx_child = MakeTransactionRef(mtx_child);
+    const auto result_parent_child = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {tx_parent, tx_child}, /* test_accept */ true);
+    BOOST_CHECK_MESSAGE(result_parent_child.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << result_parent_child.m_state.GetRejectReason());
+    auto it_parent = result_parent_child.m_tx_results.find(tx_parent->GetWitnessHash());
+    auto it_child = result_parent_child.m_tx_results.find(tx_child->GetWitnessHash());
+    BOOST_CHECK(it_parent != result_parent_child.m_tx_results.end());
+    BOOST_CHECK_MESSAGE(it_parent->second.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << it_parent->second.m_state.GetRejectReason());
+    BOOST_CHECK(it_child != result_parent_child.m_tx_results.end());
+    BOOST_CHECK_MESSAGE(it_child->second.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << it_child->second.m_state.GetRejectReason());
+
+
+    // A single, giant transaction submitted through ProcessNewPackage fails on single tx policy.
+    CTransactionRef giant_ptx = create_placeholder_tx(999, 999);
+    BOOST_CHECK(GetVirtualTransactionSize(*giant_ptx) > MAX_PACKAGE_SIZE * 1000);
+    auto result_single_large = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {giant_ptx}, /* test_accept */ true);
+    BOOST_CHECK(result_single_large.m_state.IsInvalid());
+    BOOST_CHECK_EQUAL(result_single_large.m_state.GetResult(), PackageValidationResult::PCKG_TX);
+    BOOST_CHECK_EQUAL(result_single_large.m_state.GetRejectReason(), "transaction failed");
+    auto it_giant_tx = result_single_large.m_tx_results.find(giant_ptx->GetWitnessHash());
+    BOOST_CHECK(it_giant_tx != result_single_large.m_tx_results.end());
+    BOOST_CHECK_EQUAL(it_giant_tx->second.m_state.GetRejectReason(), "tx-size");
+
+    // Check that mempool size hasn't changed.
+    BOOST_CHECK_EQUAL(m_node.mempool->size(), initialPoolSize);
+}
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
new file mode 100644
index 00000000000..54873ce6fa8
--- /dev/null
+++ b/src/test/validation_block_tests.cpp
@@ -0,0 +1,357 @@
+// Copyright (c) 2018-2020 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 <boost/test/unit_test.hpp>
+
+#include <chainparams.h>
+#include <consensus/merkle.h>
+#include <consensus/validation.h>
+#include <miner.h>
+#include <pow.h>
+#include <random.h>
+#include <script/standard.h>
+#include <test/util/script.h>
+#include <test/util/setup_common.h>
+#include <util/time.h>
+#include <validation.h>
+#include <validationinterface.h>
+
+#include <thread>
+
+namespace validation_block_tests {
+struct MinerTestingSetup : public RegTestingSetup {
+    std::shared_ptr<CBlock> Block(const uint256& prev_hash);
+    std::shared_ptr<const CBlock> GoodBlock(const uint256& prev_hash);
+    std::shared_ptr<const CBlock> BadBlock(const uint256& prev_hash);
+    std::shared_ptr<CBlock> FinalizeBlock(std::shared_ptr<CBlock> pblock);
+    void BuildChain(const uint256& root, int height, const unsigned int invalid_rate, const unsigned int branch_rate, const unsigned int max_size, std::vector<std::shared_ptr<const CBlock>>& blocks);
+};
+} // namespace validation_block_tests
+
+BOOST_FIXTURE_TEST_SUITE(validation_block_tests, MinerTestingSetup)
+
+struct TestSubscriber final : public CValidationInterface {
+    uint256 m_expected_tip;
+
+    explicit TestSubscriber(uint256 tip) : m_expected_tip(tip) {}
+
+    void UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload) override
+    {
+        BOOST_CHECK_EQUAL(m_expected_tip, pindexNew->GetBlockHash());
+    }
+
+    void BlockConnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override
+    {
+        BOOST_CHECK_EQUAL(m_expected_tip, block->hashPrevBlock);
+        BOOST_CHECK_EQUAL(m_expected_tip, pindex->pprev->GetBlockHash());
+
+        m_expected_tip = block->GetHash();
+    }
+
+    void BlockDisconnected(const std::shared_ptr<const CBlock>& block, const CBlockIndex* pindex) override
+    {
+        BOOST_CHECK_EQUAL(m_expected_tip, block->GetHash());
+        BOOST_CHECK_EQUAL(m_expected_tip, pindex->GetBlockHash());
+
+        m_expected_tip = block->hashPrevBlock;
+    }
+};
+
+std::shared_ptr<CBlock> MinerTestingSetup::Block(const uint256& prev_hash)
+{
+    static int i = 0;
+    static uint64_t time = Params().GenesisBlock().nTime;
+
+    auto ptemplate = BlockAssembler(m_node.chainman->ActiveChainstate(), *m_node.mempool, Params()).CreateNewBlock(CScript{} << i++ << OP_TRUE);
+    auto pblock = std::make_shared<CBlock>(ptemplate->block);
+    pblock->hashPrevBlock = prev_hash;
+    pblock->nTime = ++time;
+
+    // Make the coinbase transaction with two outputs:
+    // One zero-value one that has a unique pubkey to make sure that blocks at the same height can have a different hash
+    // Another one that has the coinbase reward in a P2WSH with OP_TRUE as witness program to make it easy to spend
+    CMutableTransaction txCoinbase(*pblock->vtx[0]);
+    txCoinbase.vout.resize(2);
+    txCoinbase.vout[1].scriptPubKey = P2WSH_OP_TRUE;
+    txCoinbase.vout[1].nValue = txCoinbase.vout[0].nValue;
+    txCoinbase.vout[0].nValue = 0;
+    txCoinbase.vin[0].scriptWitness.SetNull();
+    // Always pad with OP_0 at the end to avoid bad-cb-length error
+    txCoinbase.vin[0].scriptSig = CScript{} << WITH_LOCK(::cs_main, return m_node.chainman->m_blockman.LookupBlockIndex(prev_hash)->nHeight + 1) << OP_0;
+    pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
+
+    return pblock;
+}
+
+std::shared_ptr<CBlock> MinerTestingSetup::FinalizeBlock(std::shared_ptr<CBlock> pblock)
+{
+    const CBlockIndex* prev_block{WITH_LOCK(::cs_main, return m_node.chainman->m_blockman.LookupBlockIndex(pblock->hashPrevBlock))};
+    GenerateCoinbaseCommitment(*pblock, prev_block, Params().GetConsensus());
+
+    pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
+
+    while (!CheckProofOfWork(pblock->GetHash(), pblock->nBits, Params().GetConsensus())) {
+        ++(pblock->nNonce);
+    }
+
+    // submit block header, so that miner can get the block height from the
+    // global state and the node has the topology of the chain
+    BlockValidationState ignored;
+    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlockHeaders({pblock->GetBlockHeader()}, ignored, Params()));
+
+    return pblock;
+}
+
+// construct a valid block
+std::shared_ptr<const CBlock> MinerTestingSetup::GoodBlock(const uint256& prev_hash)
+{
+    return FinalizeBlock(Block(prev_hash));
+}
+
+// construct an invalid block (but with a valid header)
+std::shared_ptr<const CBlock> MinerTestingSetup::BadBlock(const uint256& prev_hash)
+{
+    auto pblock = Block(prev_hash);
+
+    CMutableTransaction coinbase_spend;
+    coinbase_spend.vin.push_back(CTxIn(COutPoint(pblock->vtx[0]->GetHash(), 0), CScript(), 0));
+    coinbase_spend.vout.push_back(pblock->vtx[0]->vout[0]);
+
+    CTransactionRef tx = MakeTransactionRef(coinbase_spend);
+    pblock->vtx.push_back(tx);
+
+    auto ret = FinalizeBlock(pblock);
+    return ret;
+}
+
+void MinerTestingSetup::BuildChain(const uint256& root, int height, const unsigned int invalid_rate, const unsigned int branch_rate, const unsigned int max_size, std::vector<std::shared_ptr<const CBlock>>& blocks)
+{
+    if (height <= 0 || blocks.size() >= max_size) return;
+
+    bool gen_invalid = InsecureRandRange(100) < invalid_rate;
+    bool gen_fork = InsecureRandRange(100) < branch_rate;
+
+    const std::shared_ptr<const CBlock> pblock = gen_invalid ? BadBlock(root) : GoodBlock(root);
+    blocks.push_back(pblock);
+    if (!gen_invalid) {
+        BuildChain(pblock->GetHash(), height - 1, invalid_rate, branch_rate, max_size, blocks);
+    }
+
+    if (gen_fork) {
+        blocks.push_back(GoodBlock(root));
+        BuildChain(blocks.back()->GetHash(), height - 1, invalid_rate, branch_rate, max_size, blocks);
+    }
+}
+
+BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
+{
+    // build a large-ish chain that's likely to have some forks
+    std::vector<std::shared_ptr<const CBlock>> blocks;
+    while (blocks.size() < 50) {
+        blocks.clear();
+        BuildChain(Params().GenesisBlock().GetHash(), 100, 15, 10, 500, blocks);
+    }
+
+    bool ignored;
+    // Connect the genesis block and drain any outstanding events
+    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(Params(), std::make_shared<CBlock>(Params().GenesisBlock()), true, &ignored));
+    SyncWithValidationInterfaceQueue();
+
+    // subscribe to events (this subscriber will validate event ordering)
+    const CBlockIndex* initial_tip = nullptr;
+    {
+        LOCK(cs_main);
+        initial_tip = m_node.chainman->ActiveChain().Tip();
+    }
+    auto sub = std::make_shared<TestSubscriber>(initial_tip->GetBlockHash());
+    RegisterSharedValidationInterface(sub);
+
+    // create a bunch of threads that repeatedly process a block generated above at random
+    // this will create parallelism and randomness inside validation - the ValidationInterface
+    // will subscribe to events generated during block validation and assert on ordering invariance
+    std::vector<std::thread> threads;
+    for (int i = 0; i < 10; i++) {
+        threads.emplace_back([&]() {
+            bool ignored;
+            FastRandomContext insecure;
+            for (int i = 0; i < 1000; i++) {
+                auto block = blocks[insecure.randrange(blocks.size() - 1)];
+                Assert(m_node.chainman)->ProcessNewBlock(Params(), block, true, &ignored);
+            }
+
+            // to make sure that eventually we process the full chain - do it here
+            for (auto block : blocks) {
+                if (block->vtx.size() == 1) {
+                    bool processed = Assert(m_node.chainman)->ProcessNewBlock(Params(), block, true, &ignored);
+                    assert(processed);
+                }
+            }
+        });
+    }
+
+    for (auto& t : threads) {
+        t.join();
+    }
+    SyncWithValidationInterfaceQueue();
+
+    UnregisterSharedValidationInterface(sub);
+
+    LOCK(cs_main);
+    BOOST_CHECK_EQUAL(sub->m_expected_tip, m_node.chainman->ActiveChain().Tip()->GetBlockHash());
+}
+
+/**
+ * Test that mempool updates happen atomically with reorgs.
+ *
+ * This prevents RPC clients, among others, from retrieving immediately-out-of-date mempool data
+ * during large reorgs.
+ *
+ * The test verifies this by creating a chain of `num_txs` blocks, matures their coinbases, and then
+ * submits txns spending from their coinbase to the mempool. A fork chain is then processed,
+ * invalidating the txns and evicting them from the mempool.
+ *
+ * We verify that the mempool updates atomically by polling it continuously
+ * from another thread during the reorg and checking that its size only changes
+ * once. The size changing exactly once indicates that the polling thread's
+ * view of the mempool is either consistent with the chain state before reorg,
+ * or consistent with the chain state after the reorg, and not just consistent
+ * with some intermediate state during the reorg.
+ */
+BOOST_AUTO_TEST_CASE(mempool_locks_reorg)
+{
+    bool ignored;
+    auto ProcessBlock = [&](std::shared_ptr<const CBlock> block) -> bool {
+        return Assert(m_node.chainman)->ProcessNewBlock(Params(), block, /*force_processing=*/true, /*new_block=*/&ignored);
+    };
+
+    // Process all mined blocks
+    BOOST_REQUIRE(ProcessBlock(std::make_shared<CBlock>(Params().GenesisBlock())));
+    auto last_mined = GoodBlock(Params().GenesisBlock().GetHash());
+    BOOST_REQUIRE(ProcessBlock(last_mined));
+
+    // Run the test multiple times
+    for (int test_runs = 3; test_runs > 0; --test_runs) {
+        BOOST_CHECK_EQUAL(last_mined->GetHash(), m_node.chainman->ActiveChain().Tip()->GetBlockHash());
+
+        // Later on split from here
+        const uint256 split_hash{last_mined->hashPrevBlock};
+
+        // Create a bunch of transactions to spend the miner rewards of the
+        // most recent blocks
+        std::vector<CTransactionRef> txs;
+        for (int num_txs = 22; num_txs > 0; --num_txs) {
+            CMutableTransaction mtx;
+            mtx.vin.push_back(CTxIn{COutPoint{last_mined->vtx[0]->GetHash(), 1}, CScript{}});
+            mtx.vin[0].scriptWitness.stack.push_back(WITNESS_STACK_ELEM_OP_TRUE);
+            mtx.vout.push_back(last_mined->vtx[0]->vout[1]);
+            mtx.vout[0].nValue -= 1000;
+            txs.push_back(MakeTransactionRef(mtx));
+
+            last_mined = GoodBlock(last_mined->GetHash());
+            BOOST_REQUIRE(ProcessBlock(last_mined));
+        }
+
+        // Mature the inputs of the txs
+        for (int j = COINBASE_MATURITY; j > 0; --j) {
+            last_mined = GoodBlock(last_mined->GetHash());
+            BOOST_REQUIRE(ProcessBlock(last_mined));
+        }
+
+        // Mine a reorg (and hold it back) before adding the txs to the mempool
+        const uint256 tip_init{last_mined->GetHash()};
+
+        std::vector<std::shared_ptr<const CBlock>> reorg;
+        last_mined = GoodBlock(split_hash);
+        reorg.push_back(last_mined);
+        for (size_t j = COINBASE_MATURITY + txs.size() + 1; j > 0; --j) {
+            last_mined = GoodBlock(last_mined->GetHash());
+            reorg.push_back(last_mined);
+        }
+
+        // Add the txs to the tx pool
+        {
+            LOCK(cs_main);
+            for (const auto& tx : txs) {
+                const MempoolAcceptResult result = m_node.chainman->ProcessTransaction(tx);
+                BOOST_REQUIRE(result.m_result_type == MempoolAcceptResult::ResultType::VALID);
+            }
+        }
+
+        // Check that all txs are in the pool
+        {
+            LOCK(m_node.mempool->cs);
+            BOOST_CHECK_EQUAL(m_node.mempool->mapTx.size(), txs.size());
+        }
+
+        // Run a thread that simulates an RPC caller that is polling while
+        // validation is doing a reorg
+        std::thread rpc_thread{[&]() {
+            // This thread is checking that the mempool either contains all of
+            // the transactions invalidated by the reorg, or none of them, and
+            // not some intermediate amount.
+            while (true) {
+                LOCK(m_node.mempool->cs);
+                if (m_node.mempool->mapTx.size() == 0) {
+                    // We are done with the reorg
+                    break;
+                }
+                // Internally, we might be in the middle of the reorg, but
+                // externally the reorg to the most-proof-of-work chain should
+                // be atomic. So the caller assumes that the returned mempool
+                // is consistent. That is, it has all txs that were there
+                // before the reorg.
+                assert(m_node.mempool->mapTx.size() == txs.size());
+                continue;
+            }
+            LOCK(cs_main);
+            // We are done with the reorg, so the tip must have changed
+            assert(tip_init != m_node.chainman->ActiveChain().Tip()->GetBlockHash());
+        }};
+
+        // Submit the reorg in this thread to invalidate and remove the txs from the tx pool
+        for (const auto& b : reorg) {
+            ProcessBlock(b);
+        }
+        // Check that the reorg was eventually successful
+        BOOST_CHECK_EQUAL(last_mined->GetHash(), m_node.chainman->ActiveChain().Tip()->GetBlockHash());
+
+        // We can join the other thread, which returns when the reorg was successful
+        rpc_thread.join();
+    }
+}
+
+BOOST_AUTO_TEST_CASE(witness_commitment_index)
+{
+    CScript pubKey;
+    pubKey << 1 << OP_TRUE;
+    auto ptemplate = BlockAssembler(m_node.chainman->ActiveChainstate(), *m_node.mempool, Params()).CreateNewBlock(pubKey);
+    CBlock pblock = ptemplate->block;
+
+    CTxOut witness;
+    witness.scriptPubKey.resize(MINIMUM_WITNESS_COMMITMENT);
+    witness.scriptPubKey[0] = OP_RETURN;
+    witness.scriptPubKey[1] = 0x24;
+    witness.scriptPubKey[2] = 0xaa;
+    witness.scriptPubKey[3] = 0x21;
+    witness.scriptPubKey[4] = 0xa9;
+    witness.scriptPubKey[5] = 0xed;
+
+    // A witness larger than the minimum size is still valid
+    CTxOut min_plus_one = witness;
+    min_plus_one.scriptPubKey.resize(MINIMUM_WITNESS_COMMITMENT + 1);
+
+    CTxOut invalid = witness;
+    invalid.scriptPubKey[0] = OP_VERIFY;
+
+    CMutableTransaction txCoinbase(*pblock.vtx[0]);
+    txCoinbase.vout.resize(4);
+    txCoinbase.vout[0] = witness;
+    txCoinbase.vout[1] = witness;
+    txCoinbase.vout[2] = min_plus_one;
+    txCoinbase.vout[3] = invalid;
+    pblock.vtx[0] = MakeTransactionRef(std::move(txCoinbase));
+
+    BOOST_CHECK_EQUAL(GetWitnessCommitmentIndex(pblock), 2);
+}
+BOOST_AUTO_TEST_SUITE_END()