fuzz: test versionbits delayed activation

src/test/fuzz/versionbits.cpp

@@ -29,14 +29,16 @@ public:
     const int64_t m_end;
     const int m_period;
     const int m_threshold;
+    const int m_min_activation_height;
     const int m_bit;
 
-    TestConditionChecker(int64_t begin, int64_t end, int period, int threshold, int bit)
-        : m_begin{begin}, m_end{end}, m_period{period}, m_threshold{threshold}, m_bit{bit}
+    TestConditionChecker(int64_t begin, int64_t end, int period, int threshold, int min_activation_height, int bit)
+        : m_begin{begin}, m_end{end}, m_period{period}, m_threshold{threshold}, m_min_activation_height{min_activation_height}, m_bit{bit}
     {
         assert(m_period > 0);
         assert(0 <= m_threshold && m_threshold <= m_period);
         assert(0 <= m_bit && m_bit < 32 && m_bit < VERSIONBITS_NUM_BITS);
+        assert(0 <= m_min_activation_height);
     }
 
     bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override { return Condition(pindex->nVersion); }
@@ -44,6 +46,7 @@ public:
     int64_t EndTime(const Consensus::Params& params) const override { return m_end; }
     int Period(const Consensus::Params& params) const override { return m_period; }
     int Threshold(const Consensus::Params& params) const override { return m_threshold; }
+    int MinActivationHeight(const Consensus::Params& params) const override { return m_min_activation_height; }
 
     ThresholdState GetStateFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateFor(pindexPrev, dummy_params, m_cache); }
     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev) const { return AbstractThresholdConditionChecker::GetStateSinceHeightFor(pindexPrev, dummy_params, m_cache); }
@@ -168,8 +171,9 @@ FUZZ_TARGET_INIT(versionbits, initialize)
             never_active_test = true;
         }
     }
+    int min_activation = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, period * max_periods);
 
-    TestConditionChecker checker(start_time, timeout, period, threshold, bit);
+    TestConditionChecker checker(start_time, timeout, period, threshold, min_activation, bit);
 
     // Early exit if the versions don't signal sensibly for the deployment
     if (!checker.Condition(ver_signal)) return;
@@ -306,11 +310,16 @@ FUZZ_TARGET_INIT(versionbits, initialize)
         }
         break;
     case ThresholdState::LOCKED_IN:
-        assert(exp_state == ThresholdState::STARTED);
-        assert(current_block->GetMedianTimePast() < checker.m_end);
-        assert(blocks_sig >= threshold);
+        if (exp_state == ThresholdState::LOCKED_IN) {
+            assert(current_block->nHeight + 1 < min_activation);
+        } else {
+            assert(exp_state == ThresholdState::STARTED);
+            assert(current_block->GetMedianTimePast() < checker.m_end);
+            assert(blocks_sig >= threshold);
+        }
         break;
     case ThresholdState::ACTIVE:
+        assert(always_active_test || min_activation <= current_block->nHeight + 1);
         assert(exp_state == ThresholdState::ACTIVE || exp_state == ThresholdState::LOCKED_IN);
         break;
     case ThresholdState::FAILED: