add test for dihedral style

unittest/force-styles/test_improper_style.cpp

@@ -1,19 +1,3 @@
-/*
-- there are 7 basic functions
-  - delete_file
-  - cleanup_lammps
-  - init_lammps
-  - run_lammps
-  - restart_lammps
-  - data_lammps
-  - generate_yaml_file
-- move delete_file amd cleanup_lammps to a single file
-- I don't understand utility lambda, but they are being reused multiple times
-- add as many comments as possible, to show my understanding and document the code
-- code for matching forces, energy and stress are repeated 3 times
-- run_lammps looks to be same across all tests - it isn't, there's subtle difference
-*/
-
 /* ----------------------------------------------------------------------
    LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
    http://lammps.sandia.gov, Sandia National Laboratories
@@ -312,12 +296,6 @@ void generate_yaml_file(const char *outfile, const TestConfig &config)
     }
     writer.emit_block("improper_coeff", block);
 
-    // equilibrium improper
-    // block = fmt::format("{}", lmp->atom->nimpropertypes);
-    // for (int i = 0; i < lmp->atom->nimpropertypes; ++i)
-    //     block += fmt::format(" {}", lmp->force->improper->equilibrium_improper(i + 1));
-    // writer.emit("equilibrium", block);
-
     // extract
     block.clear();
     for (auto data : config.extract)