Miniskirt: factory_girl, relaxed

Miniskirt: `factory_girl`, relaxed

11 Jan 2010, Chicago

Living on the edge isn’t easy. You continuously risk that everything you rely on stops working.

NoMethodError: undefined method `configuration' for #<Rails::Application>
  from rails/railties/lib/rails.rb:53:in `configuration'
  from factory_girl-1.2.3/lib/factory_girl.rb:25:in `<top (required)>'
  from rails/activesupport/lib/active_support/dependencies.rb:167:in `require'
  from rails/activesupport/lib/active_support/dependencies.rb:167:in `block in require'
  from rails/activesupport/lib/active_support/dependencies.rb:537:in `new_constants_in'
  from rails/activesupport/lib/active_support/dependencies.rb:167:in `require'
  from test/test_helper.rb:16

Et tu, factory_girl?

The fix was easy enough¹, but I started realized that I only really used a small fraction of what was under the hood. I took a page out of Ryan Davis’ book, reordered the words, and wrote Miniskirt to complement minitest.

Miniskirt is factory_girl, relaxed. It’s the essential, with some flare:

Blocks are avoidable with Ruby 1.9 string interpolation. Avoid blocks if you can. Your models should handle their own logic.

f.email '%{first_name}.%{last_name}@example.com' # ...not...
f.email { |u| "#{u.first_name}.#{u.last_name}@example.com" }

Sequences are simpler (why bother with blocks?):

f.email 'person%d@example.com' # ...instead of...
f.sequence(:email) { |n| "person#{n}@example.com" }

What’s missing?

Factory.attributes_for :model.: Call Factory.build(:model).attributes, instead.
Factory.stub.: Stub your models like you stub everything else.
Factory#association.: Almost as short, and explicit: f.user { Factory :user }.
Factory#callback.: I can’t think of a callback that should be on a factory but not the model.

Here she is. All of her.

# Factory girl, relaxed.
#
#   Factory.define :user do |f|
#     f.login 'johndoe%d'                          # Sequence.
#     f.email '%{login}@example.com'               # Interpolate.
#     f.password f.password_confirmation('foobar') # Chain.
#   end
#
#   Factory.define :post do |f|
#     f.user { Factory :user }                     # Blocks, if you must.
#   end
class Miniskirt < Struct.new(:__klass__)
  undef_method *instance_methods.grep(/^(?!__|object_id)/) # BlankerSlate.
  @@factories = {} and private_class_method :new

  class << self
    def define(name)
      @@factories[name = name.to_s] = {} and yield new(name)
    end

    def build(name, attrs = {})
      (name, n = name.to_s) and (m = name.classify.constantize).new do |rec|
        attrs.stringify_keys!.reverse_update(@@factories[name]).each do |k, v|
          rec.send "#{k}=", case v when String # Sequence and interpolate.
            v.sub(/%\d*d/) {|d| d % n ||= m.maximum(:id).to_i + 1} % attrs % n
          when Proc then v.call(rec) else v
          end
        end
      end
    end

    def create(name, attrs = {})
      build(name, attrs).tap { |record| record.save }
    end
  end

  def method_missing(name, value = nil, &block)
    @@factories[__klass__][name] = block || value
  end
end

def Miniskirt(name, attrs = {})
  Miniskirt.create(name, attrs)
end

Factory = Miniskirt
alias Factory Miniskirt

Not bad for under 30 LOC.

Miniskirt isn't for everyone. The slightly more conservative, more backwards-compatible Minidress may suit you better. Or maybe factory_girl, with all her bells and whistles, fits you just fine.²

Whatever you choose, though, remember: write less, and write better.

stephencelis

Miniskirt: `factory_girl`, relaxed

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