anchor.diff:          _     -> os:putenv("ERL_COMPILER_OPTIONS", ExistingEnv)
       end.
   
  +%% this test sets the env var, compiles, records the file last modified
  +%% timestamp, recompiles and compares the file last modified timestamp to
  +%% ensure it has changed. this test should run on 18.x
   always_recompile_when_erl_compiler_options_set(Config) ->
       %% save existing env to restore after test
       ExistingEnv = os:getenv("ERL_COMPILER_OPTIONS"),
  
positive.code:         _     -> os:putenv("ERL_COMPILER_OPTIONS", ExistingEnv)
      end.
  
  recompile_when_erl_compiler_options_env_changes(Config) ->
      %% save existing env to restore after test
      ExistingEnv = os:getenv("ERL_COMPILER_OPTIONS"),
  
negative.code:                                    ["as", "test", "compile"],
                                     {ok, [{app, Name}]}).
  
  %% this test sets the env var, compiles, records the file last modified timestamp,
  %% recompiles and compares the file last modified timestamp to ensure it hasn't
  %% changed. this test should run on 19.x+
  dont_recompile_when_erl_compiler_options_env_does_not_change(Config) ->
      %% save existing env to restore after test
      ExistingEnv = os:getenv("ERL_COMPILER_OPTIONS"),
  