diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 1f0195d..20193e8 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -3928,7 +3928,7 @@ checkMaxVersion(Node *root, Node *node, InternalVersionT oldestVersion,
                 bool &success, ConflictSet::Impl *impl) {
   checkVersionsGeqOldestExtant(node,
                                InternalVersionT(impl->oldestExtantVersion));
-  auto expected = InternalVersionT::zero;
+  auto expected = oldestVersion;
   if (node->entryPresent) {
     expected = std::max(expected, node->entry.pointVersion);
   }
@@ -4151,26 +4151,42 @@ int main(void) { printTree(); }
 
 #ifdef ENABLE_FUZZ
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
-  TestDriver<ConflictSet::Impl> driver{data, size};
+  Arbitrary arbitrary({data, size});
+  TestDriver<ConflictSet::Impl> driver1{arbitrary};
+  TestDriver<ConflictSet::Impl> driver2{arbitrary};
 
+  bool done1 = false;
+  bool done2 = false;
   for (;;) {
-    bool done = driver.next();
-    if (!driver.ok) {
-      debugPrintDot(stdout, driver.cs.root, &driver.cs);
-      fflush(stdout);
-      abort();
+    if (!done1) {
+      done1 = driver1.next();
+      if (!driver1.ok) {
+        debugPrintDot(stdout, driver1.cs.root, &driver1.cs);
+        fflush(stdout);
+        abort();
+      }
+      if (!checkCorrectness(driver1.cs.root, driver1.cs.oldestVersion,
+                            &driver1.cs)) {
+        debugPrintDot(stdout, driver1.cs.root, &driver1.cs);
+        fflush(stdout);
+        abort();
+      }
     }
-#if DEBUG_VERBOSE && !defined(NDEBUG)
-    fprintf(stderr, "Check correctness\n");
-#endif
-    bool success =
-        checkCorrectness(driver.cs.root, driver.cs.oldestVersion, &driver.cs);
-    if (!success) {
-      debugPrintDot(stdout, driver.cs.root, &driver.cs);
-      fflush(stdout);
-      abort();
+    if (!done2) {
+      done2 = driver2.next();
+      if (!driver2.ok) {
+        debugPrintDot(stdout, driver2.cs.root, &driver2.cs);
+        fflush(stdout);
+        abort();
+      }
+      if (!checkCorrectness(driver2.cs.root, driver2.cs.oldestVersion,
+                            &driver2.cs)) {
+        debugPrintDot(stdout, driver2.cs.root, &driver2.cs);
+        fflush(stdout);
+        abort();
+      }
     }
-    if (done) {
+    if (done1 && done2) {
       break;
     }
   }
diff --git a/Internal.h b/Internal.h
index ac54e62..e86f8bb 100644
--- a/Internal.h
+++ b/Internal.h
@@ -580,11 +580,10 @@ namespace {
 
 template <class ConflictSetImpl, bool kEnableAssertions = true>
 struct TestDriver {
-  Arbitrary arbitrary;
-  explicit TestDriver(const uint8_t *data, size_t size)
-      : arbitrary({data, size}) {}
+  Arbitrary *arbitrary;
+  explicit TestDriver(Arbitrary &a) : arbitrary(&a) {}
 
-  int64_t oldestVersion = arbitrary.next();
+  int64_t oldestVersion = arbitrary->next();
   int64_t writeVersion = oldestVersion;
   ConflictSetImpl cs{oldestVersion};
   ReferenceImpl refImpl{oldestVersion};
@@ -593,33 +592,34 @@ struct TestDriver {
 
   bool ok = true;
 
-  const int prefixLen = arbitrary.bounded(512);
-  const int prefixByte = arbitrary.randT<uint8_t>();
+  const int prefixLen = arbitrary->bounded(512);
+  const int prefixByte = arbitrary->randT<uint8_t>();
 
   // Call until it returns true, for "done". Check internal invariants etc
   // between calls to next.
   bool next() {
     assert(cs.getBytes() >= 0);
-    if (!arbitrary.hasEntropy()) {
+    if (!arbitrary->hasEntropy()) {
       return true;
     }
     Arena arena;
     {
-      int numPointWrites = arbitrary.bounded(100);
-      int numRangeWrites = arbitrary.bounded(100);
-      int64_t v = (writeVersion += arbitrary.bounded(10) ? arbitrary.bounded(10)
-                                                         : arbitrary.next());
+      int numPointWrites = arbitrary->bounded(100);
+      int numRangeWrites = arbitrary->bounded(100);
+      int64_t v =
+          (writeVersion +=
+           arbitrary->bounded(10) ? arbitrary->bounded(10) : arbitrary->next());
       auto *writes =
           new (arena) ConflictSet::WriteRange[numPointWrites + numRangeWrites];
       auto keys = set<std::string_view>(arena);
       while (int(keys.size()) < numPointWrites + numRangeWrites * 2) {
-        if (!arbitrary.hasEntropy()) {
+        if (!arbitrary->hasEntropy()) {
           return true;
         }
-        int keyLen = prefixLen + arbitrary.bounded(kMaxKeySuffixLen);
+        int keyLen = prefixLen + arbitrary->bounded(kMaxKeySuffixLen);
         auto *begin = new (arena) uint8_t[keyLen];
         memset(begin, prefixByte, prefixLen);
-        arbitrary.randomBytes(begin + prefixLen, keyLen - prefixLen);
+        arbitrary->randomBytes(begin + prefixLen, keyLen - prefixLen);
         keys.insert(std::string_view((const char *)begin, keyLen));
       }
 
@@ -629,7 +629,7 @@ struct TestDriver {
                rangesRemaining = numRangeWrites;
            pointsRemaining > 0 || rangesRemaining > 0; ++i) {
         bool pointRead = pointsRemaining > 0 && rangesRemaining > 0
-                             ? bool(arbitrary.bounded(2))
+                             ? bool(arbitrary->bounded(2))
                              : pointsRemaining > 0;
         if (pointRead) {
           assert(pointsRemaining > 0);
@@ -667,14 +667,14 @@ struct TestDriver {
 
       // Test non-canonical writes
       if (numPointWrites > 0) {
-        int overlaps = arbitrary.bounded(numPointWrites);
+        int overlaps = arbitrary->bounded(numPointWrites);
         for (int i = 0; i < numPointWrites + numRangeWrites && overlaps > 0;
              ++i) {
           if (writes[i].end.len == 0) {
-            int keyLen = prefixLen + arbitrary.bounded(kMaxKeySuffixLen);
+            int keyLen = prefixLen + arbitrary->bounded(kMaxKeySuffixLen);
             auto *begin = new (arena) uint8_t[keyLen];
             memset(begin, prefixByte, prefixLen);
-            arbitrary.randomBytes(begin + prefixLen, keyLen - prefixLen);
+            arbitrary->randomBytes(begin + prefixLen, keyLen - prefixLen);
             writes[i].end.len = keyLen;
             writes[i].end.p = begin;
             auto c =
@@ -692,10 +692,10 @@ struct TestDriver {
           }
         }
       }
-      if (arbitrary.bounded(2)) {
+      if (arbitrary->bounded(2)) {
         // Shuffle writes
         for (int i = numPointWrites + numRangeWrites - 1; i > 0; --i) {
-          int j = arbitrary.bounded(i + 1);
+          int j = arbitrary->bounded(i + 1);
           if (i != j) {
             using std::swap;
             swap(writes[i], writes[j]);
@@ -704,7 +704,7 @@ struct TestDriver {
       }
 
       oldestVersion +=
-          arbitrary.bounded(10) ? arbitrary.bounded(10) : arbitrary.next();
+          arbitrary->bounded(10) ? arbitrary->bounded(10) : arbitrary->next();
       oldestVersion = std::min(oldestVersion, writeVersion);
 
 #ifdef THREAD_TEST
@@ -739,24 +739,24 @@ struct TestDriver {
 #endif
     }
     {
-      int numPointReads = arbitrary.bounded(100);
-      int numRangeReads = arbitrary.bounded(100);
+      int numPointReads = arbitrary->bounded(100);
+      int numRangeReads = arbitrary->bounded(100);
 
-      int64_t v = std::max<int64_t>(writeVersion - (arbitrary.bounded(10)
-                                                        ? arbitrary.bounded(10)
-                                                        : arbitrary.next()),
+      int64_t v = std::max<int64_t>(writeVersion - (arbitrary->bounded(10)
+                                                        ? arbitrary->bounded(10)
+                                                        : arbitrary->next()),
                                     0);
       auto *reads =
           new (arena) ConflictSet::ReadRange[numPointReads + numRangeReads];
       auto keys = set<std::string_view>(arena);
       while (int(keys.size()) < numPointReads + numRangeReads * 2) {
-        if (!arbitrary.hasEntropy()) {
+        if (!arbitrary->hasEntropy()) {
           return true;
         }
-        int keyLen = prefixLen + arbitrary.bounded(kMaxKeySuffixLen);
+        int keyLen = prefixLen + arbitrary->bounded(kMaxKeySuffixLen);
         auto *begin = new (arena) uint8_t[keyLen];
         memset(begin, prefixByte, prefixLen);
-        arbitrary.randomBytes(begin + prefixLen, keyLen - prefixLen);
+        arbitrary->randomBytes(begin + prefixLen, keyLen - prefixLen);
         keys.insert(std::string_view((const char *)begin, keyLen));
       }
 
@@ -765,7 +765,7 @@ struct TestDriver {
       for (int pointsRemaining = numPointReads, rangesRemaining = numRangeReads;
            pointsRemaining > 0 || rangesRemaining > 0; ++i) {
         bool pointRead = pointsRemaining > 0 && rangesRemaining > 0
-                             ? bool(arbitrary.bounded(2))
+                             ? bool(arbitrary->bounded(2))
                              : pointsRemaining > 0;
         if (pointRead) {
           assert(pointsRemaining > 0);
diff --git a/TestDriver.cpp b/TestDriver.cpp
index e1d24b3..0c9db40 100644
--- a/TestDriver.cpp
+++ b/TestDriver.cpp
@@ -13,25 +13,58 @@ int main(int argc, char **argv) {
     std::stringstream buffer;
     buffer << t.rdbuf();
     auto str = buffer.str();
-    TestDriver<ConflictSet, !PERF_TEST> driver{(const uint8_t *)str.data(),
-                                               str.size()};
-    while (!driver.next())
-      ;
-    if (!driver.ok) {
-      abort();
+    Arbitrary arbitrary({(const uint8_t *)str.data(), str.size()});
+    TestDriver<ConflictSet, !PERF_TEST> driver1{arbitrary};
+    TestDriver<ConflictSet, !PERF_TEST> driver2{arbitrary};
+    bool done1 = false;
+    bool done2 = false;
+    for (;;) {
+      if (!done1) {
+        done1 = driver1.next();
+        if (!driver1.ok) {
+          abort();
+        }
+      }
+      if (!done2) {
+        done2 = driver2.next();
+        if (!driver2.ok) {
+          abort();
+        }
+      }
+      if (done1 && done2) {
+        break;
+      }
     }
 
-    ConflictSet::MetricsV1 *metrics;
-    int metricsCount;
-    driver.cs.getMetricsV1(&metrics, &metricsCount);
-    printf("#################### METRICS FOR %s ####################\n",
-           argv[i]);
-    for (int i = 0; i < metricsCount; ++i) {
-      printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
-      printf("# TYPE %s %s\n", metrics[i].name,
-             metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
-      printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+    {
+      ConflictSet::MetricsV1 *metrics;
+      int metricsCount;
+      driver1.cs.getMetricsV1(&metrics, &metricsCount);
+      printf("#################### METRICS for ConflictSet 1 for %s "
+             "####################\n",
+             argv[i]);
+      for (int i = 0; i < metricsCount; ++i) {
+        printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
+        printf("# TYPE %s %s\n", metrics[i].name,
+               metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
+        printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+      }
+      puts("");
+    }
+    {
+      ConflictSet::MetricsV1 *metrics;
+      int metricsCount;
+      driver2.cs.getMetricsV1(&metrics, &metricsCount);
+      printf("#################### METRICS for ConflictSet 2 for %s "
+             "####################\n",
+             argv[i]);
+      for (int i = 0; i < metricsCount; ++i) {
+        printf("# HELP %s %s\n", metrics[i].name, metrics[i].help);
+        printf("# TYPE %s %s\n", metrics[i].name,
+               metrics[i].type == metrics[i].Counter ? "counter" : "gauge");
+        printf("%s %g\n", metrics[i].name, metrics[i].getValue());
+      }
+      puts("");
     }
-    puts("");
   }
 }