Rails - are validations only for data from user input via forms?

Question

My models produce a lot of values for attributes which the user can not specify in any forms.

Should I be specifying validations for those attributes to prevent any of my model logic creating dodgy values or is that something I should just check for in my tests?

Answer 1

As well as being essential for confirming user input, Active Record validations also provide a useful DSL for specifying the intent behind your domain design.