Building and testing the domain_name_validator gem is pretty easy.
The gemspec file for the gem, domain_name_validator.gemspec, is an active file containing Ruby code. In other words, the gemspec file itself has code to figure out what files should be included in the gem, etc. Each time a release is done, the only thing that needs to be edited is the "gem.date" property.
The version number is defined in the version.rb file, located in the lib directory tree. The version number should be bumped up in some fashion with each release. Version numbers often have 3 digits, e.g. - 1.2.3. The left-most number is a release, followed by a sub-release and a patch. All versions within a release should generally be backwards compatible. A sub-release generally include significant new features, whilea patch is generally a minor update (often a bug fix).
The gemspec file automatically picks up the version number from the version.rb file, so make sure you keep it updated properly.
Testing the code is simple. Run the following command from the top level of the gem's directory tree:
$ rake test
The following lists were downloaded in order to perform tests with existing domains and top level domains:
This gem was setup with rubocop. Run the following command from the top level of the gem's directory tree:
$ rake rubocop
To create the gem file for this gem, run the following command from the top level of the gem's directory tree:
$ rake build
Obviously, you can only do this step if you've got the appropriate privileges at RubyGems.org and everything is properly configured.
$ rake release