python - Pytest与argparse : how to test user is prompted for confirmation?

我有一个CLI工具，并想测试是否提示用户使用input()确认选择。这等效于在Python 2中使用raw_input()。

代码

测试的(释义)代码如下所示:

import sys
import argparse


def confirm():
    notification_str = "Please respond with 'y' or 'n'"
    while True:
        choice = input("Confirm [Y/n]?").lower()
        if choice in 'yes' or not choice:
            return True
        if choice in 'no':
            return False
        print(notification_str)


def parse_args(args):
    parser = argparse.ArgumentParser()
    parser.add_argument('-d', '--destructive', action='store_true')
    return parser.parse_args()


def main():
    args = parse_args(sys.argv[1:])
    if args.destructive:
        if not confirm():
            sys.exit()
    do_stuff(args)


if __name__ == '__main__':
    main()

问题

我正在使用pytest作为我的框架。我该如何做才能测试CLI中是否显示确认提示？如果我尝试比较stdout，则会收到错误消息:OSError: reading from stdin while output is captured。

我要确保:

设置破坏性标志时显示确认

不是

时不显示

我将在另一个文件中使用以下代码:

import pytest
from module_name import main


def test_user_is_prompted_when_destructive_flag_is_set():
    sys.argv['', '-d']
    main()
    assert _  # What the hell goes here?


def test_user_is_not_prompted_when_destructive_flag_not_set():
    sys.argv['',]
    main()
    assert _  # And here too?

最佳答案

我建议使用confirm()函数开始测试是一种更好的单元测试策略。这样可以更本地地模拟input和sys.stdio之类的东西。然后，一旦确定可以按预期工作，就可以编写测试以验证它是否以特定方式被调用。您可以为此编写测试，并在那些测试中模拟confirm()。

这是对confirm()的单元测试，它使用 pytest.parametrize 和 mock 处理用户输入和输出:

代码:

@pytest.mark.parametrize("from_user, response, output", [
    (['x', 'x', 'No'], False, "Please respond with 'y' or 'n'\n" * 2),
    ('y', True, ''),
    ('n', False, ''),
    (['x', 'y'], True, "Please respond with 'y' or 'n'\n"),
])
def test_get_from_user(from_user, response, output):
    from_user = list(from_user) if isinstance(from_user, list) else [from_user]

    with mock.patch.object(builtins, 'input', lambda x: from_user.pop(0)):
        with mock.patch('sys.stdout', new_callable=StringIO):
            assert response == confirm()
            assert output == sys.stdout.getvalue()

这是如何运作的？
pytest.mark.parametrize允许在有条件的情况下轻松调用一个测试函数多次。这是4个简单的步骤，它们将测试confirm中的大多数功能:

@pytest.mark.parametrize("from_user, response, output", [
    (['x', 'x', 'No'], False, "Please respond with 'y' or 'n'\n" * 2),
    ('y', True, ''),
    ('n', False, ''),
    (['x', 'y'], True, "Please respond with 'y' or 'n'\n"),
])

mock.patch 可用于临时替换模块中的功能(除其他用途外)。在这种情况下，它用于替换input和sys.stdout以允许注入(inject)用户输入并捕获打印的字符串

with mock.patch.object(builtins, 'input', lambda x: from_user.pop(0)):
    with mock.patch('sys.stdout', new_callable=StringIO):

最终运行被测函数，并验证函数的输出和打印的任何字符串:

assert response == confirm()
assert output == sys.stdout.getvalue()

测试代码(用于测试代码):

import sys
from io import StringIO
import pytest
from unittest import mock
import builtins

def confirm():
    notification_str = "Please respond with 'y' or 'n'"
    while True:
        choice = input("Confirm [Y/n]?").lower()
        if choice in 'yes' or not choice:
            return True
        if choice in 'no':
            return False
        print(notification_str)

@pytest.mark.parametrize("from_user, response, output", [
    (['x', 'x', 'No'], False, "Please respond with 'y' or 'n'\n" * 2),
    ('y', True, ''),
    ('n', False, ''),
    (['x', 'y'], True, "Please respond with 'y' or 'n'\n"),
])
def test_get_from_user(from_user, response, output):
    from_user = list(from_user) if isinstance(from_user, list) \
        else [from_user]
    with mock.patch.object(builtins, 'input', lambda x: from_user.pop(0)):
        with mock.patch('sys.stdout', new_callable=StringIO):
            assert response == confirm()
            assert output == sys.stdout.getvalue()

pytest.main('-x test.py'.split())

结果:

============================= test session starts =============================
platform win32 -- Python 3.6.3, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
rootdir: C:\Users\stephen\Documents\src\testcode, inifile:
collected 4 items

test.py ....                                                             [100%]

========================== 4 passed in 0.15 seconds ===========================

测试对confirm()的调用:

要测试确认是否在预期的时间被调用以及程序在预期的时间响应，可以使用unittest.mock模拟confirm()。

注意:在通常的单元测试方案中，confirm将在不同的文件中，并且mock.patch可以与在此示例中修补sys.argv的方式类似的方式使用。

用于检查对confirm()的调用的测试代码:

import sys
import argparse

def confirm():
    pass

def parse_args(args):
    parser = argparse.ArgumentParser()
    parser.add_argument('-d', '--destructive', action='store_true')
    return parser.parse_args()


def main():
    args = parse_args(sys.argv[1:])
    if args.destructive:
        if not confirm():
            sys.exit()


import pytest
from unittest import mock

@pytest.mark.parametrize("argv, called, response", [
    ([], False, None),
    (['-d'], True, False),
    (['-d'], True, True),
])
def test_get_from_user(argv, called, response):
    global confirm
    original_confirm = confirm
    confirm = mock.Mock(return_value=response)
    with mock.patch('sys.argv', [''] + argv):
        if called and not response:
            with pytest.raises(SystemExit):
                main()
        else:
            main()

        assert confirm.called == called
    confirm = original_confirm

pytest.main('-x test.py'.split())

结果:

============================= test session starts =============================
platform win32 -- Python 3.6.3, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
rootdir: C:\Users\stephen\Documents\src\testcode, inifile:
collected 3 items

test.py ...                                                              [100%]

========================== 3 passed in 3.26 seconds ===========================
enter code here

关于python - Pytest与argparse : how to test user is prompted for confirmation?，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/48359957/