add unittest support for the fortran interface to LAMMPS

unittest/fortran/CMakeLists.txt

@@ -0,0 +1,30 @@
+include(CheckGeneratorSupport)
+if(NOT CMAKE_GENERATOR_SUPPORT_FORTRAN)
+  message(STATUS "Skipping Tests for the LAMMPS Fortran Module: no Fortran support in build tool")
+  return()
+endif()
+
+include(CheckLanguage)
+check_language(Fortran)
+if(CMAKE_Fortran_COMPILER)
+  enable_language(Fortran)
+  get_filename_component(LAMMPS_FORTRAN_MODULE ${LAMMPS_SOURCE_DIR}/../fortran/lammps.f90 ABSOLUTE)
+  if(BUILD_MPI)
+    find_package(MPI REQUIRED)
+  else()
+    add_library(fmpi_stubs STATIC mpi_stubs.f90)
+    add_library(MPI::MPI_Fortran ALIAS fmpi_stubs)
+  endif()
+
+  add_library(flammps STATIC ${LAMMPS_FORTRAN_MODULE})
+
+  add_executable(fortran-create wrap-create.cpp fortran-create.f90)
+  target_link_libraries(fortran-create PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTest GTest::GTestMain)
+  add_test(FortranOpen fortran-create)
+
+  add_executable(fortran-commands wrap-commands.cpp fortran-commands.f90)
+  target_link_libraries(fortran-commands PRIVATE flammps lammps MPI::MPI_Fortran GTest::GTest GTest::GTestMain)
+  add_test(FortranCommands fortran-commands)
+else()
+  message(STATUS "Skipping Tests for the LAMMPS Fortran Module: no Fortran compiler")
+endif()