Pytest从项目根目录执行测试找不到模块，如何正确配置测试收集规则

我需要测试一份与他人协作的项目，目前已将问题简化为如下最小可复现示例。

项目结构如下：

.
├── Problem1
│   ├── p1.py
│   └── tests
│       └── test_p1.py
└── Problem2
    ├── p2.py
    └── tests
        └── test_p2.py

p1.py 内容 #

def add_two_numbers(x1, x2):
    return x1+x2

test_p1.py 内容 #

import pytest
from p1 import add_two_numbers

def test_add_two_numbers():
    assert add_two_numbers(1,2)==3

p2.py 内容 #

def subtract_two_numbers(x1,x2):
    return x1-x2

test_p2.py 内容 #

import pytest
from p2 import subtract_two_numbers

def test_subtract_two_numbers():
    assert subtract_two_numbers(5,2)==3

在 Problem1 或 Problem2 目录内执行 pytest，可以正常收集并运行对应测试文件中的用例。
但从项目根目录直接执行 pytest 时会触发导入错误，pytest 运行失败，报错信息如下：

=============================================================================== test session starts ===============================================================================
platform linux -- Python 3.8.6, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: /home/awa5114/code/awa5114/example
plugins: dash-1.20.0, anyio-2.2.0
collected 0 items / 2 errors

===================================================================================== ERRORS ======================================================================================
___________________________________________________________________ ERROR collecting Problem1/tests/test_p1.py ____________________________________________________________________
ImportError while importing test module '/home/awa5114/code/awa5114/example/Problem1/tests/test_p1.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../../.pyenv/versions/3.8.6/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
Problem1/tests/test_p1.py:2: in <module>
    from p1 import add_two_numbers
E   ModuleNotFoundError: No module named 'p1'
___________________________________________________________________ ERROR collecting Problem2/tests/test_p2.py ____________________________________________________________________
ImportError while importing test module '/home/awa5114/code/awa5114/example/Problem2/tests/test_p2.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../../.pyenv/versions/3.8.6/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
Problem2/tests/test_p2.py:2: in <module>
    from p2 import subtract_two_numbers
E   ModuleNotFoundError: No module named 'p2'
============================================================================= short test summary info =============================================================================
ERROR Problem1/tests/test_p1.py
ERROR Problem2/tests/test_p2.py
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 2 errors during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
================================================================================ 2 errors in 0.07s ================================================================================

请问如何调整配置，才能在项目根目录执行 pytest 时正常识别对应的业务模块，完成测试用例的收集与运行？

这个报错本质是Python模块搜索路径匹配问题：在子目录执行pytest时，当前工作目录会被自动加入模块搜索路径，所以测试文件可以直接找到同层级的p1.py、p2.py；在根目录执行时，Problem1、Problem2目录不在默认搜索路径内，就会找不到对应模块。可以按场景选择以下方案：

方案1：添加pytest配置文件（推荐，无需修改业务代码） #

在项目根目录新建pytest.ini文件，写入以下内容：

[pytest]
pythonpath = Problem1 Problem2

配置完成后直接在根目录执行pytest即可正常运行，同时不会影响原来在子目录执行pytest的逻辑，适配多人协作场景。

方案2：调整为标准Python包结构（适合长期维护的项目） #

1. 在Problem1、Problem1/tests、Problem2、Problem2/tests目录下分别新增空的__init__.py文件，将目录标记为Python包
2. 修改测试文件的导入语句：
   • test_p1.py改为from Problem1.p1 import add_two_numbers
   • test_p2.py改为from Problem2.p2 import subtract_two_numbers
     调整后符合Python官方的包管理规范，后续新增模块也不需要频繁修改pytest配置。

方案3：临时指定搜索路径（适合临时调试） #

执行pytest前临时指定PYTHONPATH环境变量：

• Linux/macOS终端执行：

  PYTHONPATH=./Problem1:./Problem2 pytest
  

• Windows cmd执行：

  set PYTHONPATH=./Problem1;./Problem2 && pytest
  

该方案不需要修改任何项目文件，仅单次运行生效。

内容的提问来源于stack exchange，提问作者user32882