Rails: Avoiding duplication errors in Factory Girl…am I doing it wrong?

Question

Suppose I have a model user, which has a uniqueness constraint on the email field

If I call Factory(:user) once all is well, but i

Answer 1

If you only need to generate a few values for attributes, you can also add a method to String, which keeps track of the prior strings used for an attribute. You could then do something like this:

factory :user do
  fullname { Faker::Name.name.unique('user_fullname') }
end

I use this approach for seeding. I wanted to avoid sequence numbers, because they do not look realistic.

Here the String extension which makes this happen:

class String
  # Makes sure that the current string instance is unique for the given id.
  # If you call unique multiple times on equivalent strings, this method will suffix it with a upcounting number.
  # Example:
  #     puts "abc".unique("some_attribute") #=> "abc"
  #     puts "abc".unique("some_attribute") #=> "abc-1"
  #     puts "abc".unique("some_attribute") #=> "abc-2"
  #     puts "abc".unique("other") #=> "abc"
  #
  # Internal: 
  #  We keep a data structure of the following format:
  #     @@unique_values = {
  #       "some_for_id" => { "used_string_1" : 1, "used_string_2": 2 } # the numbers represent the counter to be used as suffix for the next item
  #     }
  def unique(for_id)
    @@unique_values ||= {} # initialize structure in case this method was never called before
    @@unique_values[for_id] ||= {} # initialize structure in case we have not seen this id yet
    counter = @@unique_values[for_id][self] || 0
    result = (counter == 0) ? self : "#{self}-#{counter}"
    counter += 1
    @@unique_values[for_id][self] = counter
    return result
  end

end

Caution: This should not be used for lots of attributes, since we track all prior strings (optimizations possible).