test: Wrap validation functions with TestChainstateManager

diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
index c381d1c9..bef99984 100644
--- a/src/node/blockstorage.h
+++ b/src/node/blockstorage.h
@@ -248,7 +248,6 @@ private:
         ChainstateManager& chainman);
 
     RecursiveMutex cs_LastBlockFile;
-    std::vector<CBlockFileInfo> m_blockfile_info;
 
     //! Since assumedvalid chainstates may be syncing a range of the chain that is very
     //! far away from the normal/background validation process, we should segment blockfiles
@@ -283,12 +282,6 @@ private:
 
     const Obfuscation m_obfuscation;
 
-    /** Dirty block index entries. */
-    std::set<CBlockIndex*> m_dirty_blockindex;
-
-    /** Dirty block file entries. */
-    std::set<int> m_dirty_fileinfo;
-
     /**
      * Map from external index name to oldest block that must not be pruned.
      *
@@ -304,6 +297,15 @@ private:
     const FlatFileSeq m_block_file_seq;
     const FlatFileSeq m_undo_file_seq;
 
+protected:
+    std::vector<CBlockFileInfo> m_blockfile_info;
+
+    /** Dirty block index entries. */
+    std::set<CBlockIndex*> m_dirty_blockindex;
+
+    /** Dirty block file entries. */
+    std::set<int> m_dirty_fileinfo;
+
 public:
     using Options = kernel::BlockManagerOpts;
     using ReadRawBlockResult = util::Expected<std::vector<std::byte>, ReadRawError>;
diff --git a/src/test/util/validation.cpp b/src/test/util/validation.cpp
index c199d912..b9f79f1d 100644
--- a/src/test/util/validation.cpp
+++ b/src/test/util/validation.cpp
@@ -4,6 +4,7 @@
 
 #include <test/util/validation.h>
 
+#include <node/blockstorage.h>
 #include <util/check.h>
 #include <util/time.h>
 #include <validation.h>
@@ -11,6 +12,13 @@
 
 using kernel::ChainstateRole;
 
+void TestBlockManager::CleanupForFuzzing()
+{
+    m_dirty_blockindex.clear();
+    m_dirty_fileinfo.clear();
+    m_blockfile_info.resize(1);
+}
+
 void TestChainstateManager::DisableNextWrite()
 {
     struct TestChainstate : public Chainstate {
@@ -43,3 +51,43 @@ void ValidationInterfaceTest::BlockConnected(
 {
     obj.BlockConnected(role, block, pindex);
 }
+void TestChainstateManager::InvalidBlockFound(CBlockIndex* pindex, const BlockValidationState& state)
+{
+    struct TestChainstate : public Chainstate {
+        void CallInvalidBlockFound(CBlockIndex* pindex, const BlockValidationState& state) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+        {
+            InvalidBlockFound(pindex, state);
+        }
+    };
+
+    static_cast<TestChainstate*>(&ActiveChainstate())->CallInvalidBlockFound(pindex, state);
+}
+
+void TestChainstateManager::InvalidChainFound(CBlockIndex* pindexNew)
+{
+    struct TestChainstate : public Chainstate {
+        void CallInvalidChainFound(CBlockIndex* pindexNew) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+        {
+            InvalidChainFound(pindexNew);
+        }
+    };
+
+    static_cast<TestChainstate*>(&ActiveChainstate())->CallInvalidChainFound(pindexNew);
+}
+
+CBlockIndex* TestChainstateManager::FindMostWorkChain()
+{
+    struct TestChainstate : public Chainstate {
+        CBlockIndex* CallFindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
+        {
+            return FindMostWorkChain();
+        }
+    };
+
+    return static_cast<TestChainstate*>(&ActiveChainstate())->CallFindMostWorkChain();
+}
+
+void TestChainstateManager::ResetBestInvalid()
+{
+    m_best_invalid = nullptr;
+}
diff --git a/src/test/util/validation.h b/src/test/util/validation.h
index 4a24c97e..debad32d 100644
--- a/src/test/util/validation.h
+++ b/src/test/util/validation.h
@@ -7,8 +7,16 @@
 
 #include <validation.h>
 
+namespace node {
+class BlockManager;
+}
 class CValidationInterface;
 
+struct TestBlockManager : public node::BlockManager {
+    /** Test-only method to clear internal state for fuzzing */
+    void CleanupForFuzzing();
+};
+
 struct TestChainstateManager : public ChainstateManager {
     /** Disable the next write of all chainstates */
     void DisableNextWrite();
@@ -16,6 +24,11 @@ struct TestChainstateManager : public ChainstateManager {
     void ResetIbd();
     /** Toggle IsInitialBlockDownload from true to false */
     void JumpOutOfIbd();
+    /** Wrappers that avoid making chainstatemanager internals public for tests */
+    void InvalidBlockFound(CBlockIndex* pindex, const BlockValidationState& state) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    void InvalidChainFound(CBlockIndex* pindexNew) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    CBlockIndex* FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
+    void ResetBestInvalid() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 };
 
 class ValidationInterfaceTest
diff --git a/src/validation.h b/src/validation.h
index 77958b53..e4b1e555 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -929,7 +929,6 @@ enum class SnapshotCompletionResult {
 class ChainstateManager
 {
 private:
-    CBlockIndex* m_best_invalid GUARDED_BY(::cs_main){nullptr};
 
     /** The last header for which a headerTip notification was issued. */
     CBlockIndex* m_last_notified_header GUARDED_BY(GetMutex()){nullptr};
@@ -983,6 +982,9 @@ private:
     SteadyClock::duration GUARDED_BY(::cs_main) time_chainstate{};
     SteadyClock::duration GUARDED_BY(::cs_main) time_post_connect{};
 
+protected:
+    CBlockIndex* m_best_invalid GUARDED_BY(::cs_main){nullptr};
+
 public:
     using Options = kernel::ChainstateManagerOpts;