[英]How do I mock part of a python constructor just for testing?
I am new to Python, so I apologize if this is a duplicate or overly simple question. 我是Python的新手,所以如果这是一个重复或过于简单的问题我会道歉。 I have written a coordinator class that calls two other classes that use the kafka-python library to send/read data from Kafka. 我编写了一个协调器类,调用另外两个使用kafka-python库来发送/读取Kafka数据的类。 I want to write a unit test for my coordinator class but I'm having trouble figuring out how to best to go about this. 我想为我的协调员课程编写一个单元测试,但是我很难弄清楚如何最好地解决这个问题。 I was hoping that I could make an alternate constructor that I could pass my mocked objects into, but this doesn't seem to be working as I get an error that test_mycoordinator cannot be resolved. 我希望我可以创建一个替代构造函数,我可以将我的模拟对象传递给,但这似乎不起作用,因为我得到一个错误,test_mycoordinator无法解决。 Am I going about testing this class the wrong way? 我是否会以错误的方式测试这门课程? Is there a pythonic way I should be testing it? 我应该测试一种pythonic方式吗?
Here is what my test class looks like so far: 这是我的测试类到目前为止的样子:
import unittest
from mock import Mock
from mypackage import mycoordinator
class MyTest(unittest.TestCase):
def setUpModule(self):
# Create a mock producer
producer_attributes = ['__init__', 'run', 'stop']
mock_producer = Mock(name='Producer', spec=producer_attributes)
# Create a mock consumer
consumer_attributes = ['__init__', 'run', 'stop']
data_out = [{u'dataObjectID': u'test1'},
{u'dataObjectID': u'test2'},
{u'dataObjectID': u'test3'}]
mock_consumer = Mock(
name='Consumer', spec=consumer_attributes, return_value=data_out)
self.coor = mycoordinator.test_mycoordinator(mock_producer, mock_consumer)
def test_send_data(self):
# Create some data and send it to the producer
count = 0
while count < 3:
count += 1
testName = 'test' + str(count)
self.coor.sendData(testName , None)
And here is the class I am trying to test: 以下是我要测试的课程:
class MyCoordinator():
def __init__(self):
# Process Command Line Arguments using argparse
...
# Initialize the producer and the consumer
self.myproducer = producer.Producer(self.servers,
self.producer_topic_name)
self.myconsumer = consumer.Consumer(self.servers,
self.consumer_topic_name)
# Constructor used for testing -- DOES NOT WORK
@classmethod
def test_mycoordinator(cls, mock_producer, mock_consumer):
cls.myproducer = mock_producer
cls.myconsumer = mock_consumer
# Send the data to the producer
def sendData(self, data, key):
self.myproducer.run(data, key)
# Receive data from the consumer
def getData(self):
data = self.myconsumer.run()
return data
There is no need to provide a separate constructor. 不需要提供单独的构造函数。 Mocking patches your code to replace objects with mocks. 模拟修补代码以用模拟替换对象。 Just use the mock.patch()
decorator on your test methods; 只需在测试方法上使用mock.patch()
装饰器 ; it'll pass in references to the generated mock objects. 它将传递对生成的模拟对象的引用。
Both producer.Producer()
and consumer.Consumer()
are then mocked out before you create the instance: 在创建实例之前 ,然后模拟出producer.Producer()
和consumer.Consumer()
:
import mock
class MyTest(unittest.TestCase):
@mock.patch('producer.Producer', autospec=True)
@mock.patch('consumer.Consumer', autospec=True)
def test_send_data(self, mock_consumer, mock_producer):
# configure the consumer instance run method
consumer_instance = mock_consumer.return_value
consumer_instance.run.return_value = [
{u'dataObjectID': u'test1'},
{u'dataObjectID': u'test2'},
{u'dataObjectID': u'test3'}]
coor = MyCoordinator()
# Create some data and send it to the producer
for count in range(3):
coor.sendData('test{}'.format(count) , None)
# Now verify that the mocks have been called correctly
mock_producer.assert_has_calls([
mock.Call('test1', None),
mock.Call('test2', None),
mock.Call('test3', None)])
So the moment test_send_data
is called, the mock.patch()
code replaces the producer.Producer
reference with a mock object. 所以当test_send_data
, mock.patch()
代码用mock对象替换producer.Producer
引用。 Your MyCoordinator
class then uses those mock objects rather than the real code. 然后,您的MyCoordinator
类使用这些模拟对象而不是真实代码。 calling producer.Producer()
returns a new mock object (the same object that mock_producer.return_value
references), etc. 调用producer.Producer()
返回一个新的模拟对象(与mock_producer.return_value
引用的对象相同)等。
I've made the assumption that producer
and consumer
are top-level module names. 我假设producer
和consumer
是顶级模块名称。 If they are not, provide the full import path. 如果不是,请提供完整的导入路径。 From the mock.patch()
documentation: 从mock.patch()
文档:
target should be a string in the form
'package.module.ClassName'
. target应该是'package.module.ClassName'
形式的字符串。 The target is imported and the specified object replaced with the new object, so the target must be importable from the environment you are callingpatch()
from. 导入目标并将指定的对象替换为新对象,因此目标必须可从您调用patch()
的环境中导入。 The target is imported when the decorated function is executed, not at decoration time. 执行修饰函数时导入目标,而不是在装饰时导入。
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