test/fuzz: Invoke LoadMempool via CChainState

Not only does this increase coverage, it is also more correct in that
when ::LoadMempool is called with a mempool and chainstate, it calls
AcceptToMemoryPool with just the chainstate.

AcceptToMemoryPool will then act on the chainstate's mempool via
CChainState::GetMempool, which may be different from the mempool
originally passed to ::LoadMempool. (In this fuzz test's case, it
definitely is different)

Also, move DummyChainstate to its own file since it's now used by the
validation_load_mempool fuzz test to replace CChainState's m_mempool.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/test/fuzz/mempool_utils.h b/src/test/fuzz/mempool_utils.h
new file mode 100644
index 0000000000..bfe12e30ba
--- /dev/null
+++ b/src/test/fuzz/mempool_utils.h
@@ -0,0 +1,19 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_TEST_FUZZ_MEMPOOL_UTILS_H
+#define BITCOIN_TEST_FUZZ_MEMPOOL_UTILS_H
+
+#include <validation.h>
+
+class DummyChainState final : public CChainState
+{
+public:
+    void SetMempool(CTxMemPool* mempool)
+    {
+        m_mempool = mempool;
+    }
+};
+
+#endif // BITCOIN_TEST_FUZZ_MEMPOOL_UTILS_H