mendicant-university/newman — comment on commit c17fd52e0706cf80e46ffbfec08e3ff80428aa92
File: lib/newman/commands.rb line 12
By ryanlecompte:

@ericgj Not to continue this discussion on GitHub, but I would suggest looking at the Commands module in the same light that you'd look at Enumerable, Comparable, etc. from the standard library. Both of those modules expect you to implement a particular method, and it's up to you if you wish to do something stateful in those methods or strictly behavioral.

As a side note, one violation of this general rule is the standard library's Observable module. Unfortunately this module maintains state in an @observer_peers instance variable which could clash if you happen to have one defined in your including class.