MiniTest::Mock 二，进一步示例分析

据说，如果对mock stub 和fakes概念不熟悉的话可以看看 这个 我自己看了一下，没懂。还是看例子容易些
例如，有这么个东西需要测试

class MailPurge
  def initialize(imap)
    @imap = imap
  end

  def purge(date)
    # IMAP wants dates in the format: 8-Aug-2002
    formatted_date = date.strftime('%d-%b-%Y')
  
    @imap.authenticate('LOGIN', 'user', 'password')
    @imap.select('INBOX')

    message_ids = @imap.search(["BEFORE #{formatted_date}"])
    @imap.store(message_ids, "+FLAGS", [:Deleted])
  end
end

我们的mock这样用

#相当于mock出一个imap对象有authenticate select等方法，重要是就一个ids是返回值有依赖
def test_purging_mail
  date = Date.new(2010,1,1)
  formatted_date = '01-Jan-2010'
  ids = [4,5,6]
  
  mock = MiniTest::Mock.new
  
  # mock expects:
  #            method      return  arguments
  #-------------------------------------------------------------
  mock.expect(:authenticate,  nil, ['LOGIN', 'user', 'password'])
  mock.expect(:select,        nil, ['INBOX'])
  mock.expect(:search,        ids, [["BEFORE #{formatted_date}"]])
  mock.expect(:store,         nil, [ids, "+FLAGS", [:Deleted]])
  
  mp = MailPurge.new(mock)
  mp.purge(date)
  
  assert mock.verify
end

如果，嫌不够的话，可以学一下mock的 源代码

def initialize
  @expected_calls = {}
  @actual_calls = Hash.new {|h,k| h[k] = [] }
end
#用来记录实际调用的，后面用到

def expect(name, retval, args=[])
  n, r, a = name, retval, args # for the closure below
  @expected_calls[name] = { :retval => retval, :args => args }
  self.class.__send__(:define_method, name) { |*x|
    raise ArgumentError unless @expected_calls[n][:args].size == x.size
    @actual_calls[n] << { :retval => r, :args => x }
    retval
  }
  self
end
#如何完成mock的呢，expect的三个参数存起来，然后，参数和预期的返回值，存起来，这里比较技巧

def verify
  @expected_calls.each_key do |name|
    expected = @expected_calls[name]
    msg = "expected #{name}, #{expected.inspect}"
    raise MockExpectationError, msg unless
      @actual_calls.has_key? name and @actual_calls[name].include?(expected)
  end
  true
end
#验证