# File lib/mocha/mock.rb, line 41
    def expects(method_name_or_hash, backtrace = nil)
      if method_name_or_hash.is_a?(Hash) then
        method_name_or_hash.each do |method_name, return_value|
          ensure_method_not_already_defined(method_name)
          @expectations.add(Expectation.new(self, method_name, backtrace).returns(return_value))
        end
      else
        ensure_method_not_already_defined(method_name_or_hash)
        @expectations.add(Expectation.new(self, method_name_or_hash, backtrace))
      end
    end