如何对 subprocess.call() 进行单元测试以检查它是否在 python 中调用

Question

Hey I am trying to write unittest to check if subprocess.call() called in the function flash_it that does not return anything.

def flash_it('flash.bat'):
    file = open('file.txt', 'w')
    subprocess.call(['flash.bat', '-d'], stdout = file, stderr = subprocess.STDOUT)

@mock.patch('subprocess.call')
def test_subprocess_call_passed(self, mock_subproc_call):
    main.flash_it('flash.bat')
    self.assertTrue(mock_subproc_call.called)

Answer 1

You probably need something like this:

import subprocess
import mock


def flash_it(filename):
    with open(filename, 'w') as f:
        subprocess.call(['cmd to flash', '-d'], stdout=f, stderr=subprocess.STDOUT)

@mock.patch('subprocess.call')
def test_subprocess_call_passed(mock_subproc_call):
    flash_it('flash.bat')
    mock_subproc_call.assert_called_once()

Note that I didn't actually run that.

Of course there is also assert_called_once_with that lets you assert what parameters were passed to function. Check documentation: https://docs.python.org/3/library/unittest.mock.html

EDIT: Ok I've run it with pytest: