Add missing test for Messenger

Also rename test file (getting rid of the 'mpi_' prefix)

CMakeLists.txt

@@ -447,7 +447,7 @@ if("${CMAKE_BUILD_TYPE}" STREQUAL "Coverage")
 
       COMMAND ${FASTCOV} -q --gcov "${GCOV_BIN}"
       --include "${PUGS_SOURCE_DIR}/src"
-      --exclude "${PUGS_SOURCE_DIR}/src/main.cpp" "${PUGS_SOURCE_DIR}/src/utils/BacktraceManager.*" "${PUGS_SOURCE_DIR}/src/utils/FPEManager.*"
+      --exclude "${PUGS_SOURCE_DIR}/src/main.cpp" "${PUGS_SOURCE_DIR}/src/utils/BacktraceManager.*" "${PUGS_SOURCE_DIR}/src/utils/FPEManager.*" "${PUGS_SOURCE_DIR}/src/utils/SignalManager.*"
       --lcov -o coverage.info -n
 
       COMMAND ${LCOV} --gcov "${GCOV_BIN}" --list coverage.info

tests/CMakeLists.txt

@@ -93,7 +93,7 @@ add_executable (unit_tests
 
 add_executable (mpi_unit_tests
   mpi_test_main.cpp
-  mpi_test_Messenger.cpp
+  test_Messenger.cpp
   )
 
 add_library(test_Pugs_MeshDataBase

tests/mpi_test_Messenger.cpp → tests/test_Messenger.cpp

@@ -471,4 +471,11 @@ TEST_CASE("Messenger", "[mpi]")
 
     std::remove("barrier_test");
   }
+
+  SECTION("errors")
+  {
+    int argc    = 0;
+    char** argv = nullptr;
+    REQUIRE_THROWS_WITH((parallel::Messenger::create(argc, argv)), "unexpected error: Messenger already created");
+  }
 }