ObjectCreationMethods a la Jeff Dean

object_creation_methods.rb

#lives in spec/support/object_creation_methods.rb

# Source: https://pivotallabs.com/users/jdean/blog/articles/1900-rolling-your-own-object-creation-methods-for-specs

module ObjectCreationMethods
  def new_post(overrides = {})
    defaults = {:title => "Some title #{counter}"}
    Post.new { |post| apply(post, defaults, overrides) }
  end

  def create_post(overrides = {})
    new_post(overrides).tap(&:save!)
  end

  def new_comment(overrides = {})
    defaults = {:post => proc { new_post }, :text => "some text"}
    Comment.new { |comment| apply(comment, defaults, overrides) }
  end

  def create_comment(overrides = {})
    new_comment(overrides).tap(&:save!)
  end

  private
  
  # with this code you can remove all your create methods
  def method_missing(method, *args, &block)
    new_method = method.to_s.gsub(/^create_/,'new_')
    if method.to_s != new_method && self.respond_to?(new_method)
      send(new_method, *args).tap(&:save!)
    else
      super
    end
  end
  
  def respond_to_missing?(method_name, include_private = false)
    method_name.to_s.start_with?('create_') || super
  end
  
  def counter
    @counter ||= 0
    @counter += 1
  end

  def apply(object, defaults, overrides)
    options = defaults.merge(overrides)
    options.each do |method, value_or_proc|
      object.send("#{method}=", value_or_proc.is_a?(Proc) ? value_or_proc.call : value_or_proc)
    end
  end
end

spec_helper.rb

#lives in spec/spec_helper.rb
RSpec.configure do |config|
  config.include ObjectCreationMethods
end