# File lib/mocha/mock.rb, line 42
    def expects(method_name_or_hash, backtrace = nil)
      iterator = ArgumentIterator.new(method_name_or_hash)
      iterator.each { |*args|
        method_name = args.shift
        ensure_method_not_already_defined(method_name)
        expectation = Expectation.new(self, method_name, backtrace)
        expectation.returns(args.shift) if args.length > 0
        @expectations.add(expectation)
      }
    end