RSpec Association Matchers

boof (Florian Aßmann) — Wed, 31 Oct 2007 09:42:07 GMT

Ok, what I essentially wanted to accomplish was something like:



describe Product, 'with Group' do



  it 'should belong to group' do

    Product.should belong_to(:product_group)

  end



end



describe ProductGroup, 'with Product' do



  it 'should have many products depending (on group)' do

    ProductGroup.should have_many(:products).depending

  end



end

Here is the code:



module AssociationMatchers



  class AssociationReflection



    def initialize(type, name)

      @messages = {

        :missing_association =>

          '%s is not associated with %s.',

        :wrong_type =>

          "%s %s %s./nExpected: %s",

        :wrong_options =>

          "Options are incorrect.\nExpected: %s Got: %s",

        :missing_column =>

          "Missing foreign key.\nExpected: %s"

      }

      @name = name

      @expected_type = type

      @expected_options = {}

    end

    

    def matches?(target)

      Class === target or

      raise ArgumentError, 'class expected'



      @target = target



      unless @assoc = target.reflect_on_association(@name)

        @failure = :missing_association

        return false

      end 



      unless @assoc.macro.eql?(@expected_type)

        @failure = :wrong_type

        return false

      end



      if @expected_options.any? { |o| @assoc.options[o.first] != o.last }

        @failure = :wrong_options

        return false

      end



      @column ||= @assoc.primary_key_name || @assoc.klass.name.foreign_key



      @failure = case @assoc.macro.to_s

      when 'belongs_to'

        if @target.column_names.include?(@column.to_s) then nil

        else

          :missing_column

        end

      when /(?:has_many|has_one)/

        if    @assoc.options[:through] then nil

        elsif @assoc.klass.column_names.include?(@column.to_s) then nil

        else

          :missing_column

        end

      end



      return @failure.nil?

    end



    def failure_message

      case @failure

      when :missing_association

        @messages[@failure] % [@target.name, @name]

      when :wrong_type

        @messages[@failure] % [

          @target.name,

          @assoc.macro,

          @name,

          @expected_type

        ]

      when :wrong_options

        @messages[@failure] % [

          @expected_options.inspect,

          @assoc.options.inspect

        ]

      when :missing_column

        @messages[@failure] % @column

      end

    end

    def negative_failure_message

    end



    ### Generic Options



    def of(class_name)

      class_name = class_name.name if Class === class_name

      @expected_options[:class_name] = class_name

      self

    end

    def for(foreign_key)

      @column = foreign_key

      self

    end

    def due_to(conditions)

      @expected_options[:conditions] = conditions

      self

    end

    def ordered_by(statement)

      @expected_options[:order] = statement

      self

    end

    def including(*models)

      @expected_options[:include] = (models.length == 1)? models.first: models

      self

    end



  end

  class BelongsToReflection < AssociationReflection



    def initialize(name)

      super :belongs_to, name

    end



    def counted(column)

      @expected_options[:counter_cache] = column

      self

    end

    def polymorphic(true_or_false = true)

      @expected_options[:polymorphic] = true_or_false

      self

    end



  end



  class HasOneReflection < AssociationReflection



    def initialize(name)

      super :has_one, name

    end



    def as(interface_name)

      @expected_options[:as] = interface_name

      self

    end

    def depending(dependency = true)

      @expected_options[:dependent] = dependency

      self

    end

    def extended_by(mod)

      @expected_options[:extend] = mod

      self

    end



  end

  class HasManyReflection < AssociationReflection



    def initialize(name)

      super :has_many, name

    end



    def as(interface_name)

      @expected_options[:as] = interface_name

      self

    end

    def depending(dependency = :destroy)

      @expected_options[:dependent] = dependency

      self

    end



  end

  class HasAndBelongsToManyReflection < AssociationReflection



    def initialize(name)

      super :has_and_belongs_to_many, name

    end



  end



  def belong_to(model)

    BelongsToReflection.new model

  end

  def have_one(model)

    HasOneReflection.new model

  end

  def have_many(models)

    HasManyReflection.new models

  end

  def have_and_belong_to_many(models)

    HasAndBelongsToManyReflection.new models

  end

  alias_method :habtm, :have_and_belong_to_many



end

It checks:
* association exists
* association macro
* foreign key exists (except for habtm)
* options match (only a subset is supported)

Setup:
* put the code in RAILS_ROOT + "/lib/association_matchers.rb"
* put "config.include AssociationMatchers # lib/association_matchers.rb" in your spec_helper.rb configure block
* refactor your model specs...

DZone Snippets: RSpec Matchers code

RSpec Association Matchers