mocha_extensions.rb

# This chunk of monkey patching thanks to Simone Carletti,
# see https://github.com/floehopper/mocha/pull/19 for more information

module Mocha
  class Expectation
    def returns(*values, &block)
      @return_values += if block_given?
        ReturnValues.build(block)
      else
        ReturnValues.build(*values)
      end
      self
    end
  end

  class SingleReturnValue
    def evaluate
      if @value.is_a?(Proc)
        @value.call
      else
        @value
      end
    end
  end
end

# allows setting up mocks/stubs that will be automatically applied any time
# this AR instance is instantiated, through find or whatever
# the record must be saved before calling any_instantiation, so that it has an id
module MochaAnyInstantiation
  module ClassMethods
    def reset_any_instantiation!
      @@any_instantiation = {}
    end

    def add_any_instantiation(ar_obj)
      raise(ArgumentError, "need to save first") if ar_obj.new_record?
      @@any_instantiation[ [ar_obj.class.base_class, ar_obj.id] ] = ar_obj
      # calling any_instantiation is likely to be because you're stubbing it,
      # and to later be cached inadvertently from code that *thinks* it
      # has a non-stubbed object. So let it dump, but not load (i.e.
      # the MemoryStore and NilStore dumps that are just for testing,
      # but just discard the result of dump)
      def ar_obj.marshal_dump
        nil
      end
      # no marshal_load; will raise an exception on load
      ar_obj
    end

    def instantiate(*args)
      if obj = @@any_instantiation[[base_class, args.first['id'].to_i]]
        obj
      else
        super
      end
    end
  end

  def any_instantiation
    ActiveRecord::Base.add_any_instantiation(self)
  end
end
ActiveRecord::Base.singleton_class.prepend(MochaAnyInstantiation::ClassMethods)
ActiveRecord::Base.include(MochaAnyInstantiation)
ActiveRecord::Base.reset_any_instantiation!