Python 3.x Pytest模拟for循环使用的内容管理器

我有一个脚本，它检查给定文件中的一行是否以关键字开头，如果是，则返回该行的其余部分：

class Check():
    def check_file(file, varible):
        file.seek(0)
        for line in file:
            if varible.strip() in line.strip():
                return line.strip()[len(varible):].strip()

现在我想写一个测试它。我发现这篇文章建议使用mock_open和patch：

在其他地方，我发现了建议将多个模拟放在一个列表中并使用它的建议。 我尝试了两种方法：

import pytest
from unittest.mock import patch, mock_open, Mock

from check_file import Check

def test_check_file():
        with patch("builtins.open", mock_open(read_data="flying flying")) as mock_file:

            with open("some_file", "r") as file:
                print(Check.check_file(file, "flying"))
                assert Check.check_file(file, "flying") == "flying"

def test_check_file2():
    my_mock1 = Mock()
    my_mock1.return_value =  "monthy monthy"
    my_mock2 = Mock()
    my_mock2.return_value = "python's python's"
    my_mock3 = Mock()
    my_mock3.return_value = "flying flying"
    my_mock4 = Mock()
    my_mock4.return_value = "circus circus"

    my_mock = [ my_mock1, my_mock2, my_mock3, my_mock4 ]
    print(Check.check_file(my_mock, "flying"))

并收到以下错误消息：

test_check_file.py::test_check_file None
FAILED
test_check_file.py::test_check_file2 FAILED

====================== FAILURES ========================
______________________ test_check_file _______________________

    def test_check_file():
            with patch("builtins.open", mock_open(read_data="flying flying")) as mock_file:

                with open("some_file", "r") as file:
                    print(Check.check_file(file, "flying"))
>                   assert Check.check_file(file, "flying") == "flying"
E                   AssertionError: assert None == 'flying'
E                     -None
E                     +'flying'

test_check_file.py:11: AssertionError
________________________ test_check_file2 _________________________

    def test_check_file2():
        my_mock1 = Mock()
        my_mock1.return_value =  "monthy monthy"
        my_mock2 = Mock()
        my_mock2.return_value = "python's python's"
        my_mock3 = Mock()
        my_mock3.return_value = "flying flying"
        my_mock4 = Mock()
        my_mock4.return_value = "circus circus"

        my_mock = [ my_mock1, my_mock2, my_mock3, my_mock4 ]
>       print(Check.check_file(my_mock, "flying"))

test_check_file.py:24:
_ _ _ _ _ _ _ _ _  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

file = [<Mock id='140386010077000'>, <Mock id='140386010077056'>, <Mock id='140386010077224'>, <Mock id='140386010077112'>], varible = 'flying'

    def check_file(file, varible):
>       file.seek(0)
E       AttributeError: 'list' object has no attribute 'seek'

check_file.py:4: AttributeError
====================== 2 failed in 0.54 seconds =========================

test\u check\u file.py:：test\u check\u file无
失败
test\u check\u file.py:：test\u check\u file2失败
==================================故障========================
______________________测试检查文件_______________________
def test_check_文件（）：
使用补丁（“builtins.open”，mock_open（read_data=“flying flying”））作为mock_文件：
打开（“某些文件”、“r”）作为文件：
打印（Check.Check_文件（文件“flying”））
>断言检查。检查文件（文件“flying”）=“flying”
E AssertionError:assertnone=='flying'
无
E+‘飞行’
test_check_file.py:11:AssertionError
________________________测试检查文件2_________________________
def测试检查文件2（）：
my_mock1=Mock（）
my_mock1.return_value=“monthy-monthy”
my_mock2=Mock（）
my_mock2.return_value=“python's python's”
my_mock3=Mock（）
my_mock3.return_value=“flying flying”
my_mock4=Mock（）
my_mock 4.return_value=“circus circus”
my_mock=[my_mock1，my_mock2，my_mock3，my_mock4]
>打印（Check.Check文件（我的mock，“flying”））
测试检查文件。py:24：
_ _ _ _ _ _ _ _ _  _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
文件=[，]，变量='flying'
def check_文件（文件，可变）：
>file.seek（0）
E AttributeError:“list”对象没有属性“seek”
检查\u file.py:4:AttributeError
===============================2在0.54秒内失败=========================

有没有一种方法可以使mock_open在循环中调用时不产生None值

如果我不需要seek（0），那么使用满是Mock对象的列表的方法可能会起作用