diff --git a/unittest/CMakeLists.txt b/unittest/CMakeLists.txt
index dd375112b7..33d6fce1e6 100644
--- a/unittest/CMakeLists.txt
+++ b/unittest/CMakeLists.txt
@@ -1,5 +1,11 @@
 include(GTest)
 
+if(BUILD_MPI)
+  function(add_mpi_test name binary nproc)
+    add_test(NAME ${name} COMMAND ${MPIEXEC_EXECUTABLE} -np ${nproc} ${binary})
+  endfunction()
+endif()
+
 add_subdirectory(utils)
 add_subdirectory(formats)
 add_subdirectory(commands)
diff --git a/unittest/c-library/CMakeLists.txt b/unittest/c-library/CMakeLists.txt
index 5172ed68f3..4f1ef2b93b 100644
--- a/unittest/c-library/CMakeLists.txt
+++ b/unittest/c-library/CMakeLists.txt
@@ -60,5 +60,5 @@ if (BUILD_MPI)
   add_executable(test_library_mpi test_library_mpi.cpp)
   target_link_libraries(test_library_mpi PRIVATE lammps GTest::GTest GTest::GMock)
   target_compile_definitions(test_library_mpi PRIVATE ${TEST_CONFIG_DEFS})
-  add_test(NAME LibraryMPI COMMAND ${MPIEXEC_EXECUTABLE} -np 4 $<TARGET_FILE:test_library_mpi>)
+  add_mpi_test(LibraryMPI $<TARGET_FILE:test_library_mpi> 4)
 endif()