Python 中的模拟嵌套方法

Question

为此绞尽脑汁。我想模拟下面的生成器方法 self.api.redditor(username).comments.new(limit=num) 和 self.api.redditor(username).submissions.new(limit=num)，其中 self.api 被分配给 class 实例，如 self.api = PrawReddit()

我正在尝试测试结果的大小：self.assertEqual(len(result), 5)

到目前为止，我尝试了 MockPraw.return_value.redditor.return_value.comments.return_value.new.return_value.__iter__.return_value = iter(['c' * 10]) 但测试失败 AssertionError: 0 != 5

非常感谢任何提示。

def get_comments_submissions(self, username, num=5):
    """Return max `num` of comments and submissions by `username`."""
    coms = [
        dict(
            title=comment.link_title,
            text=comment.body_html,
            subreddit=comment.subreddit_name_prefixed,
            url=comment.link_url,
            created=datetime.fromtimestamp(comment.created_utc, pytz.utc),
        )
        for comment in self.api.redditor(username).comments.new(limit=num)
    ]
    subs = [
        dict(
            title=submission.title,
            text=submission.selftext_html,
            subreddit=submission.subreddit_name_prefixed,
            url=submission.url,
            created=datetime.fromtimestamp(submission.created_utc, pytz.utc),
        )
        for submission in self.api.redditor(username).submissions.new(limit=num)
    ]
    return coms + subs if len(coms + subs) < num else (coms + subs)[:num]

Answer 1

要模拟生成器（除非您使用特定的生成器功能），您可以使用迭代器作为替代，例如

import unittest.mock as mock

generator_mock = Mock(return_value=iter(("foo", "bar")))

当你有像你的例子中那样的嵌套结构时，这会变得有点复杂，属性访问会自动处理，但必须定义来自函数的 return_value。从你的例子：

# API mock
mock_api = Mock()
mock_api.redditor.return_value = mock_subs = Mock()

# Submissions mock
mock_subs.new.return_value = iter(("foo", "bar"))

然后可以调用和断言

for item in mock_api.api.redditor("user").submissions.new(limit=5):
    print(item)

mock_api.redditor.assert_called_with("user")
mock_subs.new.assert_called_with(limit=5)

由于 API 是同一个 class 的成员，因此必须对其进行猴子修补，例如：

target = Praw()
target.api = mock_api()
target.get_comments_submissions("user")

mock_api.redditor.assert_called_with("user")
mock_subs.new.assert_called_with(limit=5)

请注意 return 值中的 iterator 是单个实例，第二次调用获取迭代器将 return 相同的实例。

Answer 2

像使用 pytest-mock 一样编写，一切都发生在 mymodule 中（您在模块顶部导入了 class，如 from xy import PrawReddit）：

mocker.patch("datetime.fromtimestamp")
mocked_comment = mocker.MagicMock()
mocked_submission = mocker.MagicMock()
mocked = mocker.patch("mymodule.PrawReddit")
mocked.return_value.redditor.return_value.comments.new.return_value = [mocker.MagicMock(), mocked_comment]
mocked.return_value.redditor.return_value.submisions.new.return_value = [mocker.MagicMock(), mocked_submission]

returned = instance.get_comments_submissions("foo", num=2)
assert mocked.return_value.redditor.call_count = 2
mocked.return_value.assert_called_with("foo")
assert returned[-1]["link_title"] == mocked_comment.link_title

具有相同介绍的另一个测试电话：

# ...
returned = instance.get_comments_submissions("foo")
assert mocked.return_value.redditor.call_count = 2
mocked.return_value.assert_called_with("foo")
assert returned[1]["link_title"] == mocked_comment.link_title
assert returned[-1]["title"] == mocked_submission.title

Python 中的模拟嵌套方法

Mock nested method in Python

python

unit-testing

generator

mocking

python-unittest