diff --git a/test/config.cc b/test/config.cc
index da918400..e900d4a8 100644
--- a/test/config.cc
+++ b/test/config.cc
@@ -416,6 +416,9 @@ void dump(const char *title) {
     log_verbose("drop table: %s\n", i->params.drop_table ? "Yes" : "No");
     log_verbose("ignore MDBX_MAP_FULL error: %s\n",
                 i->params.ignore_dbfull ? "Yes" : "No");
+    log_verbose("verifying by speculum: %s\n",
+                i->params.speculum ? "Yes" : "No");
+
     indent.pop();
   }
 
diff --git a/test/config.h b/test/config.h
index 6582f1d8..50e00382 100644
--- a/test/config.h
+++ b/test/config.h
@@ -266,6 +266,7 @@ struct actor_params_pod {
 
   bool drop_table;
   bool ignore_dbfull;
+  bool speculum;
 };
 
 struct actor_config_pod {
diff --git a/test/hill.cc b/test/hill.cc
index f65ec060..89a802ec 100644
--- a/test/hill.cc
+++ b/test/hill.cc
@@ -14,131 +14,14 @@
 
 #include "test.h"
 
-int testcase_hill::insert(const keygen::buffer &akey,
-                          const keygen::buffer &adata, unsigned flags) {
-  int err = mdbx_put(txn_guard.get(), dbi, &akey->value, &adata->value, flags);
-  if (err == MDBX_SUCCESS) {
-    const auto S_key = S(akey);
-    const auto S_data = S(adata);
-    const bool inserted = mirror.emplace(S_key, S_data).second;
-    assert(inserted);
-    (void)inserted;
-  }
-  return err;
-}
-
-int testcase_hill::replace(const keygen::buffer &akey,
-                           const keygen::buffer &new_data,
-                           const keygen::buffer &old_data, unsigned flags) {
-  const auto S_key = S(akey);
-  const auto S_old = S(old_data);
-  const auto S_new = S(new_data);
-  const auto removed = mirror.erase(set::key_type(S_key, S_old));
-  assert(removed == 1);
-  (void)removed;
-  const bool inserted = mirror.emplace(S_key, S_new).second;
-  assert(inserted);
-  (void)inserted;
-  return mdbx_replace(txn_guard.get(), dbi, &akey->value, &new_data->value,
-                      &old_data->value, flags);
-}
-
-int testcase_hill::remove(const keygen::buffer &akey,
-                          const keygen::buffer &adata) {
-  const auto S_key = S(akey);
-  const auto S_data = S(adata);
-  const auto removed = mirror.erase(set::key_type(S_key, S_data));
-  assert(removed == 1);
-  (void)removed;
-  return mdbx_del(txn_guard.get(), dbi, &akey->value, &adata->value);
-}
-
-bool testcase_hill::verify() const {
-  char dump_key[128], dump_value[128];
-  char dump_mkey[128], dump_mvalue[128];
-
-  MDBX_cursor *cursor;
-  int err = mdbx_cursor_open(txn_guard.get(), dbi, &cursor);
-  if (err != MDBX_SUCCESS)
-    failure_perror("mdbx_cursor_open()", err);
-
-  bool rc = true;
-  MDBX_val akey, avalue;
-  MDBX_val mkey, mvalue;
-  err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_FIRST);
-
-  assert(std::is_sorted(mirror.cbegin(), mirror.cend(), ItemCompare(this)));
-  auto it = mirror.cbegin();
-  while (true) {
-    if (err != MDBX_SUCCESS) {
-      akey.iov_len = avalue.iov_len = 0;
-      akey.iov_base = avalue.iov_base = nullptr;
-    }
-    const auto S_key = S(akey);
-    const auto S_data = S(avalue);
-    if (it != mirror.cend()) {
-      mkey.iov_base = (void *)it->first.c_str();
-      mkey.iov_len = it->first.size();
-      mvalue.iov_base = (void *)it->second.c_str();
-      mvalue.iov_len = it->second.size();
-    }
-    if (err == MDBX_SUCCESS && it != mirror.cend() && S_key == it->first &&
-        S_data == it->second) {
-      ++it;
-      err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_NEXT);
-    } else if (err == MDBX_SUCCESS &&
-               (it == mirror.cend() || S_key < it->first ||
-                (S_key == it->first && S_data < it->second))) {
-      if (it != mirror.cend()) {
-        log_error("extra pair: db{%s, %s} < mi{%s, %s}",
-                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
-                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)),
-                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
-                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
-      } else {
-        log_error("extra pair: db{%s, %s} < mi.END",
-                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
-                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)));
-      }
-      err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_NEXT);
-      rc = false;
-    } else if (it != mirror.cend() &&
-               (err == MDBX_NOTFOUND || S_key > it->first ||
-                (S_key == it->first && S_data > it->second))) {
-      if (err == MDBX_NOTFOUND) {
-        log_error("lost pair: db.END > mi{%s, %s}",
-                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
-                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
-      } else {
-        log_error("lost pair: db{%s, %s} > mi{%s, %s}",
-                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
-                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)),
-                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
-                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
-      }
-      ++it;
-      rc = false;
-    } else if (err == MDBX_NOTFOUND && it == mirror.cend()) {
-      break;
-    } else if (err != MDBX_SUCCESS) {
-      failure_perror("mdbx_cursor_get()", err);
-    } else {
-      assert(!"WTF?");
-    }
-  }
-
-  mdbx_cursor_close(cursor);
-  return rc;
-}
-
 bool testcase_hill::run() {
   int err = db_open__begin__table_create_open_clean(dbi);
   if (unlikely(err != MDBX_SUCCESS)) {
     log_notice("hill: bailout-prepare due '%s'", mdbx_strerror(err));
     return true;
   }
-  mirror.clear();
-  mirror_commited.clear();
+  speculum.clear();
+  speculum_commited.clear();
 
   /* LY: тест "холмиком":
    *  - сначала наполняем таблицу циклическими CRUD-манипуляциями,
@@ -204,12 +87,12 @@ bool testcase_hill::run() {
         log_notice("uphill: bailout at insert-a due '%s'", mdbx_strerror(err));
         txn_restart(true, false);
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_put(insert-a.1)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("uphill: bailout after insert-a, before commit");
       goto bailout;
     }
@@ -219,13 +102,13 @@ bool testcase_hill::run() {
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("uphill: bailout at commit due '%s'", mdbx_strerror(err));
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       commited_serial = a_serial;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("uphill: bailout after insert-a, after commit");
         goto bailout;
       }
@@ -240,12 +123,12 @@ bool testcase_hill::run() {
         log_notice("uphill: bailout at insert-b due '%s'", mdbx_strerror(err));
         txn_restart(true, false);
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_put(insert-b)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("uphill: bailout after insert-b, before commit");
       goto bailout;
     }
@@ -255,13 +138,13 @@ bool testcase_hill::run() {
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("uphill: bailout at commit due '%s'", mdbx_strerror(err));
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       commited_serial = a_serial;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("uphill: bailout after insert-b, after commit");
         goto bailout;
       }
@@ -278,12 +161,12 @@ bool testcase_hill::run() {
         log_notice("uphill: bailout at update-a due '%s'", mdbx_strerror(err));
         txn_restart(true, false);
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_replace(update-a: 1->0)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("uphill: bailout after update-a, before commit");
       goto bailout;
     }
@@ -293,13 +176,13 @@ bool testcase_hill::run() {
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("uphill: bailout at commit due '%s'", mdbx_strerror(err));
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       commited_serial = a_serial;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("uphill: bailout after update-a, after commit");
         goto bailout;
       }
@@ -314,12 +197,12 @@ bool testcase_hill::run() {
         log_notice("uphill: bailout at delete-b due '%s'", mdbx_strerror(err));
         txn_restart(true, false);
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_del(b)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("uphill: bailout after delete-b, before commit");
       goto bailout;
     }
@@ -329,13 +212,13 @@ bool testcase_hill::run() {
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("uphill: bailout at commit due '%s'", mdbx_strerror(err));
         serial_count = commited_serial;
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       commited_serial = a_serial;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("uphill: bailout after delete-b, after commit");
         goto bailout;
       }
@@ -371,12 +254,12 @@ bool testcase_hill::run() {
         log_notice("downhill: bailout at update-a due '%s'",
                    mdbx_strerror(err));
         txn_end(true);
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_put(update-a: 0->1)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("downhill: bailout after update-a, before commit");
       break;
     }
@@ -385,12 +268,12 @@ bool testcase_hill::run() {
       err = breakable_restart();
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("downhill: bailout at commit due '%s'", mdbx_strerror(err));
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("downhill: bailout after update-a, after commit");
         break;
       }
@@ -405,12 +288,12 @@ bool testcase_hill::run() {
         log_notice("downhill: bailout at insert-a due '%s'",
                    mdbx_strerror(err));
         txn_end(true);
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_put(insert-b)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("downhill: bailout after insert-b, before commit");
       break;
     }
@@ -419,12 +302,12 @@ bool testcase_hill::run() {
       err = breakable_restart();
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("downhill: bailout at commit due '%s'", mdbx_strerror(err));
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("downhill: bailout after insert-b, after commit");
         break;
       }
@@ -440,12 +323,12 @@ bool testcase_hill::run() {
         log_notice("downhill: bailout at delete-a due '%s'",
                    mdbx_strerror(err));
         txn_end(true);
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_del(a)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("downhill: bailout after delete-a, before commit");
       break;
     }
@@ -454,12 +337,12 @@ bool testcase_hill::run() {
       err = breakable_restart();
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("downhill: bailout at commit due '%s'", mdbx_strerror(err));
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("downhill: bailout after delete-a, after commit");
         break;
       }
@@ -474,12 +357,12 @@ bool testcase_hill::run() {
         log_notice("downhill: bailout at delete-b due '%s'",
                    mdbx_strerror(err));
         txn_end(true);
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
       failure_perror("mdbx_del(b)", err);
     }
-    if (!verify()) {
+    if (!speculum_verify()) {
       log_notice("downhill: bailout after delete-b, before commit");
       break;
     }
@@ -488,12 +371,12 @@ bool testcase_hill::run() {
       err = breakable_restart();
       if (unlikely(err != MDBX_SUCCESS)) {
         log_notice("downhill: bailout at commit due '%s'", mdbx_strerror(err));
-        mirror = mirror_commited;
+        speculum = speculum_commited;
         break;
       }
-      mirror_commited = mirror;
+      speculum_commited = speculum;
       txn_nops = 0;
-      if (!verify()) {
+      if (!speculum_verify()) {
         log_notice("downhill: bailout after delete-b, after commit");
         goto bailout;
       }
@@ -502,7 +385,7 @@ bool testcase_hill::run() {
     report(1);
   }
 
-  rc = verify();
+  rc = speculum_verify();
 bailout:
   if (txn_guard) {
     err = breakable_commit();
diff --git a/test/main.cc b/test/main.cc
index 1d9f51d5..e34f914f 100644
--- a/test/main.cc
+++ b/test/main.cc
@@ -71,6 +71,7 @@ void actor_params::set_defaults(const std::string &tmpdir) {
 
   drop_table = false;
   ignore_dbfull = false;
+  speculum = false;
 
   max_readers = 42;
   max_tables = 42;
@@ -296,6 +297,8 @@ int main(int argc, char *const argv[]) {
     if (config::parse_option(argc, argv, narg, "ignore-dbfull",
                              params.ignore_dbfull))
       continue;
+    if (config::parse_option(argc, argv, narg, "speculum", params.speculum))
+      continue;
     if (config::parse_option(argc, argv, narg, "dump-config",
                              global::config::dump_config))
       continue;
diff --git a/test/test.cc b/test/test.cc
index 747f8328..479fdf60 100644
--- a/test/test.cc
+++ b/test/test.cc
@@ -588,3 +588,128 @@ bool test_execute(const actor_config &config_const) {
     return false;
   }
 }
+
+//-----------------------------------------------------------------------------
+
+int testcase::insert(const keygen::buffer &akey, const keygen::buffer &adata,
+                     unsigned flags) {
+  int err = mdbx_put(txn_guard.get(), dbi, &akey->value, &adata->value, flags);
+  if (err == MDBX_SUCCESS && config.params.speculum) {
+    const auto S_key = S(akey);
+    const auto S_data = S(adata);
+    const bool inserted = speculum.emplace(S_key, S_data).second;
+    assert(inserted);
+    (void)inserted;
+  }
+  return err;
+}
+
+int testcase::replace(const keygen::buffer &akey,
+                      const keygen::buffer &new_data,
+                      const keygen::buffer &old_data, unsigned flags) {
+  if (config.params.speculum) {
+    const auto S_key = S(akey);
+    const auto S_old = S(old_data);
+    const auto S_new = S(new_data);
+    const auto removed = speculum.erase(SET::key_type(S_key, S_old));
+    assert(removed == 1);
+    (void)removed;
+    const bool inserted = speculum.emplace(S_key, S_new).second;
+    assert(inserted);
+    (void)inserted;
+  }
+  return mdbx_replace(txn_guard.get(), dbi, &akey->value, &new_data->value,
+                      &old_data->value, flags);
+}
+
+int testcase::remove(const keygen::buffer &akey, const keygen::buffer &adata) {
+  if (config.params.speculum) {
+    const auto S_key = S(akey);
+    const auto S_data = S(adata);
+    const auto removed = speculum.erase(SET::key_type(S_key, S_data));
+    assert(removed == 1);
+    (void)removed;
+  }
+  return mdbx_del(txn_guard.get(), dbi, &akey->value, &adata->value);
+}
+
+bool testcase::speculum_verify() const {
+  if (!config.params.speculum)
+    return true;
+
+  char dump_key[128], dump_value[128];
+  char dump_mkey[128], dump_mvalue[128];
+
+  MDBX_cursor *cursor;
+  int err = mdbx_cursor_open(txn_guard.get(), dbi, &cursor);
+  if (err != MDBX_SUCCESS)
+    failure_perror("mdbx_cursor_open()", err);
+
+  bool rc = true;
+  MDBX_val akey, avalue;
+  MDBX_val mkey, mvalue;
+  err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_FIRST);
+
+  assert(std::is_sorted(speculum.cbegin(), speculum.cend(), ItemCompare(this)));
+  auto it = speculum.cbegin();
+  while (true) {
+    if (err != MDBX_SUCCESS) {
+      akey.iov_len = avalue.iov_len = 0;
+      akey.iov_base = avalue.iov_base = nullptr;
+    }
+    const auto S_key = S(akey);
+    const auto S_data = S(avalue);
+    if (it != speculum.cend()) {
+      mkey.iov_base = (void *)it->first.c_str();
+      mkey.iov_len = it->first.size();
+      mvalue.iov_base = (void *)it->second.c_str();
+      mvalue.iov_len = it->second.size();
+    }
+    if (err == MDBX_SUCCESS && it != speculum.cend() && S_key == it->first &&
+        S_data == it->second) {
+      ++it;
+      err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_NEXT);
+    } else if (err == MDBX_SUCCESS &&
+               (it == speculum.cend() || S_key < it->first ||
+                (S_key == it->first && S_data < it->second))) {
+      if (it != speculum.cend()) {
+        log_error("extra pair: db{%s, %s} < mi{%s, %s}",
+                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
+                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)),
+                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
+                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
+      } else {
+        log_error("extra pair: db{%s, %s} < mi.END",
+                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
+                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)));
+      }
+      err = mdbx_cursor_get(cursor, &akey, &avalue, MDBX_NEXT);
+      rc = false;
+    } else if (it != speculum.cend() &&
+               (err == MDBX_NOTFOUND || S_key > it->first ||
+                (S_key == it->first && S_data > it->second))) {
+      if (err == MDBX_NOTFOUND) {
+        log_error("lost pair: db.END > mi{%s, %s}",
+                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
+                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
+      } else {
+        log_error("lost pair: db{%s, %s} > mi{%s, %s}",
+                  mdbx_dump_val(&akey, dump_key, sizeof(dump_key)),
+                  mdbx_dump_val(&avalue, dump_value, sizeof(dump_value)),
+                  mdbx_dump_val(&mkey, dump_mkey, sizeof(dump_mkey)),
+                  mdbx_dump_val(&mvalue, dump_mvalue, sizeof(dump_mvalue)));
+      }
+      ++it;
+      rc = false;
+    } else if (err == MDBX_NOTFOUND && it == speculum.cend()) {
+      break;
+    } else if (err != MDBX_SUCCESS) {
+      failure_perror("mdbx_cursor_get()", err);
+    } else {
+      assert(!"WTF?");
+    }
+  }
+
+  mdbx_cursor_close(cursor);
+  return rc;
+}
diff --git a/test/test.h b/test/test.h
index 795a9992..b65d51aa 100644
--- a/test/test.h
+++ b/test/test.h
@@ -95,9 +95,45 @@ typedef std::unique_ptr<MDBX_cursor, cursor_deleter> scoped_cursor_guard;
 
 class testcase {
 protected:
+#if HAVE_cxx17_std_string_view
+  using data_view = std::string_view;
+#else
+  using data_view = std::string;
+#endif
+  static inline data_view S(const MDBX_val &v) {
+    return data_view(static_cast<const char *>(v.iov_base), v.iov_len);
+  }
+  static inline data_view S(const keygen::buffer &b) { return S(b->value); }
+
+  using Item = std::pair<std::string, std::string>;
+  struct ItemCompare {
+    const testcase *context;
+    ItemCompare(const testcase *owner) : context(owner) {}
+
+    bool operator()(const Item &a, const Item &b) const {
+      MDBX_val va, vb;
+      va.iov_base = (void *)a.first.data();
+      va.iov_len = a.first.size();
+      vb.iov_base = (void *)b.first.data();
+      vb.iov_len = b.first.size();
+      int cmp = mdbx_cmp(context->txn_guard.get(), context->dbi, &va, &vb);
+      if (cmp == 0 &&
+          (context->config.params.table_flags & MDBX_DUPSORT) != 0) {
+        va.iov_base = (void *)a.second.data();
+        va.iov_len = a.second.size();
+        vb.iov_base = (void *)b.second.data();
+        vb.iov_len = b.second.size();
+        cmp = mdbx_dcmp(context->txn_guard.get(), context->dbi, &va, &vb);
+      }
+      return cmp < 0;
+    }
+  };
+  using SET = std::set<Item, ItemCompare>;
+
   const actor_config &config;
   const mdbx_pid_t pid;
 
+  MDBX_dbi dbi;
   scoped_db_guard db_guard;
   scoped_txn_guard txn_guard;
   scoped_cursor_guard cursor_guard;
@@ -113,6 +149,14 @@ protected:
     mdbx_canary canary;
   } last;
 
+  SET speculum;
+  bool speculum_verify() const;
+  int insert(const keygen::buffer &akey, const keygen::buffer &adata,
+             unsigned flags);
+  int replace(const keygen::buffer &akey, const keygen::buffer &new_value,
+              const keygen::buffer &old_value, unsigned flags);
+  int remove(const keygen::buffer &akey, const keygen::buffer &adata);
+
   static int oom_callback(MDBX_env *env, mdbx_pid_t pid, mdbx_tid_t tid,
                           uint64_t txn, unsigned gap, size_t space, int retry);
 
@@ -160,7 +204,8 @@ protected:
 
 public:
   testcase(const actor_config &config, const mdbx_pid_t pid)
-      : config(config), pid(pid), signalled(false), nops_completed(0) {
+      : config(config), pid(pid), signalled(false), nops_completed(0),
+        speculum(ItemCompare(this)) {
     start_timestamp.reset();
     memset(&last, 0, sizeof(last));
   }
@@ -181,57 +226,11 @@ public:
 
 class testcase_hill : public testcase {
   using inherited = testcase;
-
-#if HAVE_cxx17_std_string_view
-  using data_view = std::string_view;
-#else
-  using data_view = std::string;
-#endif
-
-  MDBX_dbi dbi;
-  using Item = std::pair<std::string, std::string>;
-  struct ItemCompare {
-    const testcase_hill *context;
-    ItemCompare(const testcase_hill *owner) : context(owner) {}
-
-    bool operator()(const Item &a, const Item &b) const {
-      MDBX_val va, vb;
-      va.iov_base = (void *)a.first.data();
-      va.iov_len = a.first.size();
-      vb.iov_base = (void *)b.first.data();
-      vb.iov_len = b.first.size();
-      int cmp = mdbx_cmp(context->txn_guard.get(), context->dbi, &va, &vb);
-      if (cmp == 0 &&
-          (context->config.params.table_flags & MDBX_DUPSORT) != 0) {
-        va.iov_base = (void *)a.second.data();
-        va.iov_len = a.second.size();
-        vb.iov_base = (void *)b.second.data();
-        vb.iov_len = b.second.size();
-        cmp = mdbx_dcmp(context->txn_guard.get(), context->dbi, &va, &vb);
-      }
-      return cmp < 0;
-    }
-  };
-
-  using set = std::set<Item, ItemCompare>;
-  set mirror, mirror_commited;
-
-  bool verify() const;
-  int insert(const keygen::buffer &akey, const keygen::buffer &adata,
-             unsigned flags);
-  int replace(const keygen::buffer &akey, const keygen::buffer &new_value,
-              const keygen::buffer &old_value, unsigned flags);
-  int remove(const keygen::buffer &akey, const keygen::buffer &adata);
-
-  static inline data_view S(const MDBX_val &v) {
-    return data_view(static_cast<const char *>(v.iov_base), v.iov_len);
-  }
-  static inline data_view S(const keygen::buffer &b) { return S(b->value); }
+  SET speculum_commited;
 
 public:
   testcase_hill(const actor_config &config, const mdbx_pid_t pid)
-      : testcase(config, pid), mirror(ItemCompare(this)),
-        mirror_commited(ItemCompare(this)) {}
+      : testcase(config, pid), speculum_commited(ItemCompare(this)) {}
   bool run() override;
 };
 
diff --git a/test/ttl.cc b/test/ttl.cc
index e5631045..5782460d 100644
--- a/test/ttl.cc
+++ b/test/ttl.cc
@@ -29,7 +29,6 @@ static unsigned edge2count(uint64_t edge, unsigned count_max) {
 }
 
 bool testcase_ttl::run() {
-  MDBX_dbi dbi;
   int err = db_open__begin__table_create_open_clean(dbi);
   if (unlikely(err != MDBX_SUCCESS)) {
     log_notice("ttl: bailout-prepare due '%s'", mdbx_strerror(err));