pytest-mock 中的模拟线程调用

Question

我有一个简单的代码库，如下所示：

import threading
import time
class Demo:
def __init__(self):
self._run_thread = False
def start(self):
if not self._run_thread:
print("Thread has not run")
threading.Thread(target=self.counter, args=(20, )).start()
return 20
else:
print("Thread has run")
return None

def counter(self, value):
self._run_thread = True
for i in range(value):
print(f"Inside counter with value {i}")
time.sleep(3)

if __name__ == "__main__":
d = Demo()
d.start()
d.start()

第一次调用start函数时，线程将运行，下次调用它时，由于设置了标志(_run_thread(，因此不会运行。

代码本身运行得很好。

但是，当我尝试针对此代码运行测试时，它无法按预期工作。以下是我的测试代码：

import app
def dummy_counter(self, value):
self._run_thread = True
def test_app_start_function_runs_well(mocker):
d = app.Demo()
mocker.patch.object(
d,
"counter",
dummy_counter
)
d.start()
result = d.start()
assert result is None

因此，由于我实际上不希望循环，我只想模拟counter函数，然后在其中设置标志，以便实际线程不会运行。

我看到以下错误。

(roughwork) ➜  threads git:(master) ✗ pytest
============================================================ test session starts ============================================================
platform linux -- Python 3.7.6, pytest-5.4.3, py-1.8.1, pluggy-0.13.1
rootdir: /home/subhayan/Codes/Test/Python-remote/threads
plugins: mock-3.1.1
collected 1 item                                                                                                                            
test_app.py Exception in thread Thread-2:
Traceback (most recent call last):
File "/home/subhayan/anaconda3/envs/roughwork/lib/python3.7/threading.py", line 926, in _bootstrap_inner
self.run()
File "/home/subhayan/anaconda3/envs/roughwork/lib/python3.7/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
TypeError: dummy_counter() missing 1 required positional argument: 'value'
F                                                                                                                         [100%]
================================================================= FAILURES ==================================================================
____________________________________________________________ test_app_runs_well _____________________________________________________________
mocker = <pytest_mock.plugin.MockFixture object at 0x7f922c05ee90>
def test_app_runs_well(mocker):
d = app.Demo()
mocker.patch.object(
d,
"counter",
dummy_counter
)
d.start()
result = d.start()
>       assert result is None
E    assert 20 is None
test_app.py:15: AssertionError
----------------------------------------------------------- Captured stdout call ------------------------------------------------------------
Thread has not run
Thread has not run
----------------------------------------------------------- Captured stderr call ------------------------------------------------------------
Exception in thread Thread-1:
Traceback (most recent call last):
File "/home/subhayan/anaconda3/envs/roughwork/lib/python3.7/threading.py", line 926, in _bootstrap_inner
self.run()
File "/home/subhayan/anaconda3/envs/roughwork/lib/python3.7/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
TypeError: dummy_counter() missing 1 required positional argument: 'value'
========================================================== short test summary info ==========================================================
FAILED test_app.py::test_app_runs_well - assert 20 is None

我不知道我哪里出错了。任何线索，我将不胜感激。

Answer 1

你几乎做对了一切。唯一的问题是self.counter是实例的绑定方法，因此self填充了正确的d实例。但是，dummy_counter没有绑定 - 因此它不会自动获取第一个参数，因此您需要提供它。

一种方法是使用部分函数，如下所示：

from functools import partial
import app

def dummy_counter(self, value):
self._run_thread = True

def test_app_start_function_runs_well(mocker):
d = app.Demo()
dummy_for_d = partial(dummy_counter, d)  # fills the first parameter with 'd'
mocker.patch.object(
d,
"counter",
dummy_for_d
)
d.start()
result = d.start()
assert result is None