Add fuzz test

ConflictSet.cpp

@@ -6,6 +6,7 @@
 #include <cstring>
 #include <map>
 #include <random>
+#include <set>
 #include <span>
 #include <string>
 #include <string_view>
@@ -825,7 +826,7 @@ void rotate(Node **node, bool dir) {
   updateMaxVersion(l);
 }
 
-void checkParentPointers(Node *node, bool &success) {
+[[maybe_unused]] void checkParentPointers(Node *node, bool &success) {
   for (int i = 0; i < 2; ++i) {
     if (node->child[i] != nullptr) {
       if (node->child[i]->parent != node) {
@@ -839,7 +840,7 @@ void checkParentPointers(Node *node, bool &success) {
   }
 }
 
-int64_t checkMaxVersion(Node *node, bool &success) {
+[[maybe_unused]] int64_t checkMaxVersion(Node *node, bool &success) {
   int64_t expected = std::max(node->pointVersion, node->rangeVersion);
   for (int i = 0; i < 2; ++i) {
     if (node->child[i] != nullptr) {
@@ -1213,4 +1214,38 @@ int main(void) {
   bool success = checkCorrectness(cs.root, refImpl);
   return success ? 0 : 1;
 }
+#endif
+
+#ifdef ENABLE_FUZZ
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  initFuzz(data, size);
+
+  int64_t writeVersion = 0;
+  ConflictSet::Impl cs{writeVersion};
+  ReferenceImpl refImpl{writeVersion};
+
+  while (gArbitrary.hasEntropy()) {
+    Arena arena;
+    int numWrites = gArbitrary.bounded(10);
+    int64_t v = ++writeVersion;
+    auto *writes = new (arena) ConflictSet::WriteRange[numWrites];
+    std::set<int> keys;
+    while (int(keys.size()) < numWrites) {
+      keys.insert(gRandom.bounded(100));
+    }
+    auto iter = keys.begin();
+    for (int i = 0; i < numWrites; ++i) {
+      writes[i].begin = toKey(arena, *iter++);
+      writes[i].end.len = 0;
+      writes[i].writeVersion = v;
+    }
+    cs.addWrites(writes, numWrites);
+    refImpl.addWrites(writes, numWrites);
+    bool success = checkCorrectness(cs.root, refImpl);
+    if (!success) {
+      abort();
+    }
+  }
+  return 0;
+}
 #endif