Clone this repository:

  $ git clone https://github.com/danbadge/dr-cron-parser

Install all the relevant gems:

  $ bundle install

From the command line in the directory for this repository:

  $ ruby app.rb --help
  $ ruby app.rb "0 0 * * *" something_to_run.sh

Run all the tests by doing:

  $ bundle exec rspec

Overall I'm fairly happy with the outcome but there's always room for improvement.

• Firstly, Field holds all the complexity. This seems like necessary complexity but I'm not happy that it's buried under a few layers and that it's called "field". The name and the layers doesn't make it obvious enough for me that there's more going here.
• CronParser and CronSummary don't do too much and add some misdirection. They just delegate and provides a slightly nicer interface.
• This isn't very thought through but I think I've got two similar patterns for the array of rules and the classes in fields.rb. I'm sure these could conform somehow so there's at least some consistency.
• On a similar note, I'd like to get rid of fields.rb all together there's no need to use a class object and singleton method. Again, nice interface but not very idiomatic.