Documentation Coverage Testing With dcov

by Pat Eyler

How often have you thrown up your hands in disgust at the poor quality of documentation for an open source project? Wouldn’t it be nice if someone put together a documentation coverage tool that worked like test coverage too ls? Well, you’re in luck—dcov is here (at least for Ruby code).

dcov is still pretty immature (the current release is called ‘Young and Feeble’), but it’ showing a lot of promise. It’s already capable of verifying that each module, class, and method of your code is documented. The upcoming release adds coverage checking for each parameter to a method (and other goodies, see below).

One of the biggest problems with writing generic documentation coverage tools is that there is a real lack of standards for documentation. Jeremy MacAnally, the author of dcov, is trying to build some consensus on this. Take a look at his blog post on the topic. (Feel free to toss in your own two cents while you’re there.)

In the upcoming release, dcov provides a mechanism for writing your own analyzer—it’s still rough, but it looks a lot like an RSpec specification. Here’s the way Jeremy’s implemented parameter checking using the new mechanism:

documentation_for_methods do |the_documentation|
  the_documentation.must "document all parameters." do
    param_names_for(the_documentation.token).each do |param|
      the_documentation.token.reporting_data[:parameters_without_coverage] <
;<
         param[0] unless
           the_documentation.token.comment.include?("#{param[0]}")
    end if the_documentation.token.params
  end
end

With this new feature, it should be easy to adapt dcov to whatever documentation standards exist within your own organization.

Jeremy has been working on dcov as part of the Google Summer of Code, he’s being mentored by Chad Fowler.