Add a cpp driver test for comparing mesh tallies with internal and external moab ptrs: currently fails because feature not implemented

tests/regression_tests/external_moab/main.cpp

@@ -0,0 +1,50 @@
+#include "openmc/capi.h"
+#include "openmc/error.h"
+#include "openmc/mesh.h"
+#include <iostream>
+#include "moab/Core.hpp"
+
+int main(int argc, char * argv[]){
+
+  using namespace openmc;
+  int openmc_err;
+
+  // Create MOAB interface
+  std::shared_ptr<moab::Interface> moabPtrLocal =
+    std::make_shared<moab::Core>();
+
+  // Load unstructured mesh file
+  std::string filename = "test_mesh_tets.h5m";
+  moab::ErrorCode rval = moabPtrLocal->load_file(filename.c_str());
+  if (rval != moab::MB_SUCCESS) {
+    fatal_error("Failed to load the unstructured mesh file: " + filename);
+  }
+  else{
+    std::cout<<"Loaded external mesh from file "<<filename<<std::endl;
+  }
+
+  // Initialise OpenMC
+  openmc_err = openmc_init(argc, argv, nullptr);
+
+  if (openmc_err == -1) {
+    // This happens for the -h and -v flags
+    return EXIT_SUCCESS;
+  } else if (openmc_err) {
+    fatal_error(openmc_err_msg);
+  }
+
+  // Create a new unstructured mesh tally using new constructor
+
+  // Add unstructured mesh tally to openmc
+  
+  // Run OpenMC
+  openmc_err = openmc_run();
+  if (openmc_err) fatal_error(openmc_err_msg);
+
+  // Deallocate memory
+  openmc_err = openmc_finalize();
+    if (openmc_err) fatal_error(openmc_err_msg);
+
+  return EXIT_SUCCESS;
+
+}