Fork me on GitHub

Write ur own spec macros

26 Jul 2010

Ng Tze Yang (ngty77@gmail.com)

Let's start with a simple model:

class Implementation < ActiveRecord::Base

  belongs_to :user

  def belongs_to?(user)
    user && user_id == user.id
  end      

end

The original specs is:

describe Implementation do

  should_belong_to :user

  it 'should belong to someone if he is the owner of it' do
    someone = Factory(:user)
    Factory(:implementation, :user => someone).belongs_to?(someone).should be_true
  end

  it 'should not belong to someone if he is not the owner of it' do
    someone = Factory(:user)
    Factory(:implementation).belongs_to?(someone).should be_false
  end

end

What we want to achieve eventually, after implementing our home-baked macro is something like this:

describe Implementation do
  include RailsBestPractices::Macros
  should_be_user_ownable
end

Here's what we can do:

# spec/macros.rb
module RailsBestPractices
  module Macros

    def self.included(base)
      base.extend(ClassMethods)
    end  

    module ClassMethods

      def should_be_user_ownable(factory_id = nil)
        factory_id ||= default_factory_id

        # define an example group
        describe 'being user ownable' do

          should_belong_to :user

          it 'should belong to someone if he is the owner of it' do
            someone = Factory(:user)
            Factory(factory_id, :user => someone).belongs_to?(someone).should be_true
          end

          it 'should not belong to someone if he is not the owner of it' do
            someone = Factory(:user)
            Factory(factory_id).belongs_to?(someone).should be_false
          end

       end
     end

     private

       def default_factory_id
          context_klass.to_s.tableize.singularize.to_sym
       end

       def context_klass
         self.description.split('::').inject(Object) {|klass, const| klass.const_get(const) }
       end

     end
   end
end

And making sure the macro definitions file is required:

# spec/spec_helper.rb
# (bottom)
require File.join(File.dirname(__FILE__), 'macros')

That's all !!

NOTE: It is actually very easy to amend the macro definition to work for test/unit or minitest, but that can be left as an exercise for the reader i guess. Feel free to ping me if u need help :]

Tags