add additional methods asked for at code review

- add test to ensure no error is raised when a yaml db setting is defined
  for the process option method
- check that the correct information is pass to add_validtation_errors
  when an error is found
refactored extract tests based on code review

-used let
-used doubles
-added addtional tests
refactor add_error_if_mandatory tests based on code review

- used doubles
- used let
- made a long method call clearer in a before block
refactore #process_column tests based on code review

-use lets
-use doubles
-fix typos
-ensure correct errors are called