Add binary operators tests

tests/CMakeLists.txt

@@ -101,12 +101,13 @@ add_executable (unit_tests
 
 add_executable (mpi_unit_tests
   mpi_test_main.cpp
-  test_Messenger.cpp
-  test_Partitioner.cpp
+  test_DiscreteFunctionP0.cpp
   test_ItemArray.cpp
   test_ItemArrayUtils.cpp
   test_ItemValue.cpp
   test_ItemValueUtils.cpp
+  test_Messenger.cpp
+  test_Partitioner.cpp
   test_SubItemValuePerItem.cpp
   test_SubItemArrayPerItem.cpp
   )