@@ -723,6 +723,11 @@ inline void Executor::_sync_topology(Topology& tpg) {
 
   auto &f = tpg._taskflow;
 
+  // TODO: check whether we can use tpg instead of t._topologies.front()
+  //       below and elsewhere.
+
+  assert(&tpg == &(f._topologies.front()));
+
   // case 1: we still need to run the topology again
   if(!std::invoke(f._topologies.front()._pred)) {
     f._topologies.front()._recover_num_sinks();
 
@@ -443,8 +443,6 @@ TEST_CASE("ParallelForOnIndex" * doctest::timeout(300)) {
   using namespace std::chrono_literals;
 
   auto exception_test = [] (unsigned num_workers) {
-
-    tf::Executor executor(num_workers);
     tf::Taskflow tf;
 
     // invalid index