message: Modification to which unit tests are run
diff: int main(int argc, char *argv[])
  {
  -#ifdef MFEM_USE_MPI
  - mfem::MPI_Session mpi;
  -#endif
  -
  // There must be exactly one instance.
  Catch::Session session;
  @@ -30,18 +26,19 @@ int main(int argc, char *argv[])
  }
  #ifdef MFEM_USE_MPI
  - // Force to only run parallel tests if the tests
  - // are executed on multiple processors.
  - if (mpi.WorldSize() > 1)
  + mfem::MPI_Session mpi;
  + // Force tests not tagged as [Parallel] to run only on MPI rank 0
  + if (mpi.WorldRank() > 0)
  {
  auto cfg = session.configData();
  cfg.testsOrTags.push_back("[Parallel]");
  session.useConfigData(cfg);
  - if (mpi.Root())
  + }
  + if (mpi.WorldSize() > 1 && mpi.Root())
  {
  mfem::out
  - << "WARNING: Only running the [Parallel] label on MPI ranks > 1." << std::endl;
  - }
  + << "WARNING: Only running the [Parallel] label on MPI ranks > 1."
  + << std::endl;
  }
  #endif
  