Avoid violating mempool policy limits in tests

Changes AddToMempool() helper to only apply changes if the mempool limits are
respected.

Fix package_rbf fuzz target to handle mempool policy violations

src/test/fuzz/rbf.cpp

@@ -120,8 +120,8 @@ FUZZ_TARGET(package_rbf, .init = initialize_package_rbf)
     replacement_tx->vin[0].prevout = g_outpoints.at(iter++);
     CTransaction replacement_tx_final{*replacement_tx};
     auto replacement_entry = ConsumeTxMemPoolEntry(fuzzed_data_provider, replacement_tx_final);
-    int32_t replacement_vsize = replacement_entry.GetTxSize();
+    int32_t replacement_weight = replacement_entry.GetAdjustedWeight();
-    int64_t running_vsize_total{replacement_vsize};
+    int64_t running_vsize_total{replacement_entry.GetTxSize()};
 
     LOCK2(cs_main, pool.cs);
 
@@ -144,6 +144,14 @@ FUZZ_TARGET(package_rbf, .init = initialize_package_rbf)
         }
         assert(!pool.GetIter(parent_entry.GetTx().GetHash()));
         AddToMempool(pool, parent_entry);
+
+        // It's possible that adding this to the mempool failed due to cluster
+        // size limits; if so bail out.
+        if(!pool.GetIter(parent_entry.GetTx().GetHash())) {
+            mempool_txs.pop_back();
+            continue;
+        }
+
         child.vin[0].prevout = COutPoint{mempool_txs.back().GetHash(), 0};
         mempool_txs.emplace_back(child);
         const auto child_entry = ConsumeTxMemPoolEntry(fuzzed_data_provider, mempool_txs.back());
@@ -155,6 +163,12 @@ FUZZ_TARGET(package_rbf, .init = initialize_package_rbf)
         }
         if (!pool.GetIter(child_entry.GetTx().GetHash())) {
             AddToMempool(pool, child_entry);
+            // Adding this transaction to the mempool may fail due to cluster
+            // size limits; if so bail out.
+            if(!pool.GetIter(child_entry.GetTx().GetHash())) {
+                mempool_txs.pop_back();
+                continue;
+            }
         }
 
         if (fuzzed_data_provider.ConsumeBool()) {
@@ -165,7 +179,7 @@ FUZZ_TARGET(package_rbf, .init = initialize_package_rbf)
     // Pick some transactions at random to be the direct conflicts
     CTxMemPool::setEntries direct_conflicts;
     for (auto& tx : mempool_txs) {
-        if (fuzzed_data_provider.ConsumeBool()) {
+        if (fuzzed_data_provider.ConsumeBool() && pool.GetIter(tx.GetHash())) {
             direct_conflicts.insert(*pool.GetIter(tx.GetHash()));
         }
     }
@@ -206,11 +220,11 @@ FUZZ_TARGET(package_rbf, .init = initialize_package_rbf)
         FeeFrac replaced;
         for (auto txiter : all_conflicts) {
             replaced.fee += txiter->GetModifiedFee();
-            replaced.size += txiter->GetTxSize();
+            replaced.size += txiter->GetAdjustedWeight();
         }
         // The total fee & size of the new diagram minus replaced fee & size should be the total
         // fee & size of the old diagram minus replacement fee & size.
-        assert((first_sum - replaced) == (second_sum - FeeFrac{replacement_fees, replacement_vsize}));
+        assert((first_sum - replaced) == (second_sum - FeeFrac{replacement_fees, replacement_weight}));
     }
 
     // If internals report error, wrapper should too

src/test/util/txmempool.cpp

@@ -218,5 +218,5 @@ void AddToMempool(CTxMemPool& tx_pool, const CTxMemPoolEntry& entry)
     changeset->StageAddition(entry.GetSharedTx(), entry.GetFee(),
             entry.GetTime().count(), entry.GetHeight(), entry.GetSequence(),
             entry.GetSpendsCoinbase(), entry.GetSigOpCost(), entry.GetLockPoints());
-    changeset->Apply();
+    if (changeset->CheckMemPoolPolicyLimits()) changeset->Apply();
 }

src/test/util/txmempool.h

@@ -64,7 +64,7 @@ void CheckMempoolEphemeralInvariants(const CTxMemPool& tx_pool);
 void CheckMempoolTRUCInvariants(const CTxMemPool& tx_pool);
 
 /** One-line wrapper for creating a mempool changeset with a single transaction
- *  and applying it. */
+ *  and applying it if the policy limits are respected. */
 void AddToMempool(CTxMemPool& tx_pool, const CTxMemPoolEntry& entry);
 
 #endif // BITCOIN_TEST_UTIL_TXMEMPOOL_H