Python 和 pytest - 模拟 db 对象

Question

这是我第一次尝试使用模拟来模拟数据库，但无法理解它是如何工作的。

我的主文件:

 def _test( db ) :
       res = {}
       for x in db.getData() :
          res[ x['id'] ] = x['name'] 
       return res

这是我的测试:

def test_small() :
   mock_db = mock.Mock()
   mock_db.getData.return_value = [{ u'name':u'Nick',u'id':1234}]
   _test( mock_db )
   assert mock_db.getData.assert_called_once()

断言失败了。错误是:

assert None
E        +  where None = <bound method Mock.assert_called_once of <Mock name='mock.getData' id='140103447969552'>>()
E        +    where <bound method Mock.assert_called_once of <Mock name='mock.getData' id='140103447969552'>> = <Mock name='mock.getData' id='140103447969552'>.assert_called_once
E        +      where <Mock name='mock.getData' id='140103447969552'> = <Mock id='140103462485712'>.getData

有人可以解释一下我错过了什么吗？理想情况下，我想稍后添加一些断言 - _test 的结果是我的模拟的返回值。

Answer 1

assert_used_once 方法本身 already done the assertion为您服务:

def assert_called_once(_mock_self):
    """assert that the mock was called only once.
    """
    self = _mock_self
    if not self.call_count == 1:
        msg = ("Expected '%s' to have been called once. Called %s times." %
               (self._mock_name or 'mock', self.call_count))
        raise AssertionError(msg)

您可以删除多余的 assert 子句:

mock_db.getData.assert_called_once()

或

assert mock_db.getData.call_count == 1