test: Add util to mine invalid blocks

With the current utils it is only possible to mine valid blocks. This
commit adds new util methods to mine invalid blocks.

src/bench/block_assemble.cpp

@@ -27,7 +27,7 @@ static void AssembleBlock(benchmark::Bench& bench)
     std::array<CTransactionRef, NUM_BLOCKS - COINBASE_MATURITY + 1> txs;
     for (size_t b{0}; b < NUM_BLOCKS; ++b) {
         CMutableTransaction tx;
-        tx.vin.push_back(MineBlock(test_setup->m_node, P2WSH_OP_TRUE));
+        tx.vin.push_back(CTxIn{MineBlock(test_setup->m_node, P2WSH_OP_TRUE)});
         tx.vin.back().scriptWitness = witness;
         tx.vout.emplace_back(1337, P2WSH_OP_TRUE);
         if (NUM_BLOCKS - b >= COINBASE_MATURITY)

src/test/fuzz/tx_pool.cpp

@@ -42,12 +42,12 @@ void initialize_tx_pool()
     g_setup = testing_setup.get();
 
     for (int i = 0; i < 2 * COINBASE_MATURITY; ++i) {
-        CTxIn in = MineBlock(g_setup->m_node, P2WSH_OP_TRUE);
+        COutPoint prevout{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);
+        outpoints.push_back(prevout);
     }
     SyncWithValidationInterfaceQueue();
 }

src/test/util/mining.cpp

@@ -6,19 +6,22 @@
 
 #include <chainparams.h>
 #include <consensus/merkle.h>
+#include <consensus/validation.h>
 #include <key_io.h>
 #include <node/context.h>
 #include <pow.h>
+#include <primitives/transaction.h>
 #include <script/standard.h>
 #include <test/util/script.h>
 #include <util/check.h>
 #include <validation.h>
+#include <validationinterface.h>
 #include <versionbits.h>
 
 using node::BlockAssembler;
 using node::NodeContext;
 
-CTxIn generatetoaddress(const NodeContext& node, const std::string& address)
+COutPoint generatetoaddress(const NodeContext& node, const std::string& address)
 {
     const auto dest = DecodeDestination(address);
     assert(IsValidDestination(dest));
@@ -58,19 +61,52 @@ std::vector<std::shared_ptr<CBlock>> CreateBlockChain(size_t total_height, const
     return ret;
 }
 
-CTxIn MineBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
+COutPoint MineBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
 {
     auto block = PrepareBlock(node, coinbase_scriptPubKey);
+    auto valid = MineBlock(node, block);
+    assert(!valid.IsNull());
+    return valid;
+}
 
+struct BlockValidationStateCatcher : public CValidationInterface {
+    const uint256 m_hash;
+    std::optional<BlockValidationState> m_state;
+
+    BlockValidationStateCatcher(const uint256& hash)
+        : m_hash{hash},
+          m_state{} {}
+
+protected:
+    void BlockChecked(const CBlock& block, const BlockValidationState& state) override
+    {
+        if (block.GetHash() != m_hash) return;
+        m_state = state;
+    }
+};
+
+COutPoint MineBlock(const NodeContext& node, std::shared_ptr<CBlock>& block)
+{
     while (!CheckProofOfWork(block->GetHash(), block->nBits, Params().GetConsensus())) {
         ++block->nNonce;
         assert(block->nNonce);
     }
 
-    bool processed{Assert(node.chainman)->ProcessNewBlock(block, true, true, nullptr)};
-    assert(processed);
+    auto& chainman{*Assert(node.chainman)};
+    const auto old_height = WITH_LOCK(chainman.GetMutex(), return chainman.ActiveHeight());
+    bool new_block;
+    BlockValidationStateCatcher bvsc{block->GetHash()};
+    RegisterValidationInterface(&bvsc);
+    const bool processed{chainman.ProcessNewBlock(block, true, true, &new_block)};
+    const bool duplicate{!new_block && processed};
+    assert(!duplicate);
+    UnregisterValidationInterface(&bvsc);
+    SyncWithValidationInterfaceQueue();
+    const bool was_valid{bvsc.m_state && bvsc.m_state->IsValid()};
+    assert(old_height + was_valid == WITH_LOCK(chainman.GetMutex(), return chainman.ActiveHeight()));
 
-    return CTxIn{block->vtx[0]->GetHash(), 0};
+    if (was_valid) return {block->vtx[0]->GetHash(), 0};
+    return {};
 }
 
 std::shared_ptr<CBlock> PrepareBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey,

src/test/util/mining.h

@@ -13,8 +13,8 @@
 
 class CBlock;
 class CChainParams;
+class COutPoint;
 class CScript;
-class CTxIn;
 namespace node {
 struct NodeContext;
 } // namespace node
@@ -23,7 +23,13 @@ struct NodeContext;
 std::vector<std::shared_ptr<CBlock>> CreateBlockChain(size_t total_height, const CChainParams& params);
 
 /** Returns the generated coin */
-CTxIn MineBlock(const node::NodeContext&, const CScript& coinbase_scriptPubKey);
+COutPoint MineBlock(const node::NodeContext&, const CScript& coinbase_scriptPubKey);
+
+/**
+ * Returns the generated coin (or Null if the block was invalid).
+ * It is recommended to call RegenerateCommitments before mining the block to avoid merkle tree mismatches.
+ **/
+COutPoint MineBlock(const node::NodeContext&, std::shared_ptr<CBlock>& block);
 
 /** Prepare a block to be mined */
 std::shared_ptr<CBlock> PrepareBlock(const node::NodeContext&, const CScript& coinbase_scriptPubKey);
@@ -31,6 +37,6 @@ std::shared_ptr<CBlock> PrepareBlock(const node::NodeContext& node, const CScrip
                                      const node::BlockAssembler::Options& assembler_options);
 
 /** RPC-like helper function, returns the generated coin */
-CTxIn generatetoaddress(const node::NodeContext&, const std::string& address);
+COutPoint generatetoaddress(const node::NodeContext&, const std::string& address);
 
 #endif // BITCOIN_TEST_UTIL_MINING_H