1. bundle open activemodel
2. Open the validator.rb file.
3. You can see the comments that shows you how to mixin the validators. Once you mixin, you can add any validator and define a dummy method for the attribute to play with it in the irb:
class Person
include ActiveModel::Validations
SSN_REGEX = /your ssn regex goes here/
validates_format_of :ssn, with: SSN_REGEX
def ssn
111-11-1111
end
end
4. Change the ssn method to invalid ssn to test your regex.
