如何使用 pytest 解决 ImportError

Question

Therewerealready 有关此主题的问题。有时程序员会在某些地方放一些__init__.py，通常说应该使用绝对路径。但是，我不让它在这里工作：

如何从包中导入类，以便在 pytest 中运行测试并使用代码？

目前我得到 pytest 或通过各自运行的代码。

我的示例项目结构是

.
├── testingonly
│   ├── cli.py
│   ├── __init__.py
│   └── testingonly.py
└── tests
    ├── __init__.py
    └── test_testingonly.py

__init__.py 在这两种情况下都是一个空文件。

$ cat testingonly/cli.py
"""Console script for testingonly."""
from testingonly import Tester

def main(args=None):
    """Console script for testingonly."""
    te = Tester()
    return 0

main()

$ cat testingonly/testingonly.py
"""Main module."""
class Tester():
    def __init__(self):
        print("Hello")

这给出了 - 正如预期的那样：

$ python3 testingonly/cli.py
Hello

但是，尝试对此进行测试失败：

$ pytest
========================================================= test session starts =========================================================
platform linux -- Python 3.7.3, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /home/stefan/Development/testingonly
collected 0 items / 1 error                                                                                                           

=============================================================== ERRORS ================================================================
_____________________________________________ ERROR collecting tests/test_testingonly.py ______________________________________________
ImportError while importing test module '/home/stefan/Development/testingonly/tests/test_testingonly.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_testingonly.py:10: in <module>
    from testingonly import cli
testingonly/cli.py:2: in <module>
    from testingonly import Tester
E   ImportError: cannot import name 'Tester' from 'testingonly' (/home/stefan/Development/testingonly/testingonly/__init__.py)

---

将testingonly/testingonly.py 重命名为testingonly/mytest.py 并更改test_testingonly.py（来自testingonly import mytest）和cli.py（来自mytest import Tester）中的导入

$ pytest
========================================================= test session starts =========================================================
platform linux -- Python 3.7.3, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /home/stefan/Development/testingonly
collected 0 items / 1 error                                                                                                           

=============================================================== ERRORS ================================================================
_____________________________________________ ERROR collecting tests/test_testingonly.py ______________________________________________
ImportError while importing test module '/home/stefan/Development/testingonly/tests/test_testingonly.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib/python3.7/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_testingonly.py:10: in <module>
    from testingonly import cli
testingonly/cli.py:2: in <module>
    from mytest import Tester
E   ModuleNotFoundError: No module named 'mytest'
======================================================= short test summary info =======================================================
ERROR tests/test_testingonly.py
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
========================================================== 1 error in 0.37s ===========================================================
$ python3 testingonly/cli.py
Hello

---

另一个建议的解决方案是重命名为 mytest.py 让测试通过，但在 cli.py 中使用 from testingonly.mytest import Tester 会产生 NameNotFound 错误。

$ python3 testingonly/cli.py 
Traceback (most recent call last):
  File "testingonly/cli.py", line 2, in <module>
    from testingonly.mytest import Tester
ModuleNotFoundError: No module named 'testingonly'

$ pytest
========================================================= test session starts =========================================================
platform linux -- Python 3.7.3, pytest-6.2.5, py-1.11.0, pluggy-1.0.0
rootdir: /home/stefan/Development/testingonly
collected 1 item                                                                                                                      

tests/test_testingonly.py .                                                                                                     [100%]

========================================================== 1 passed in 0.12s ==========================================================

Answer 1

自命名模块testingonly 和文件名testingonly.py 可能会导致模块导入方式出现一些问题。

从tests 目录中删除__init__.py。 Ref this answer .

尝试将testingonly.py 重命名为mytest.py，然后再次将其导入您的项目。

在cli.py中，应该是：

from testingonly.mytest import Tester

然后为你的测试文件test_testingonly.py:

from testingonly.mytest import Tester

你的test_testingonly.py 文件应该是这样的：

import pytest
from testingonly.mytest import Tester  # Import the Tester Class


def test_tester(capsys):
    # Create the Tester Class
    te = Tester()
    # Get the captured output
    captured = capsys.readouterr()
    # Assert that the capture output is tested
    assert captured.out == "Hello\n"

最后，运行你的测试：

python -m pytest tests/

这是一个基于您的代码的完整工作示例：https://github.com/cdesch/testingonly