python - pytest 在辅助函数中断言自省(introspection)

Question

pytest 做的很棒 assert introspection 所以很容易找到字符串中的差异，尤其是当差异在空白处时。现在我使用一个稍微复杂的测试助手，我在许多测试用例中重复使用它。助手也有自己的模块，我想为该模块添加断言内省(introspection)。

helpers.py:

...
def my_helper():
    assert 'abcy' == 'abcx'

test_mycase.py:

from .helpers import my_helper


def test_assert_in_tc():
    assert 'abcy' == 'abcx'


def test_assert_in_helper():
    my_helper()

测试报告显示了对测试中的断言有用的信息，但对助手中的断言没有帮助:

=============================================================== FAILURES ================================================================
___________________________________________________________ test_assert_in_tc ___________________________________________________________

    def test_assert_in_tc():
>       assert 'abcy' == 'abcx'
E       assert 'abcy' == 'abcx'
E         - abcy
E         ?    ^
E         + abcx
E         ?    ^

tests/test_pytest_assert.py:9: AssertionError
_________________________________________________________ test_assert_in_helper _________________________________________________________

    def test_assert_in_helper():
>       my_helper()

tests/test_pytest_assert.py:13: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    def my_helper():
>       assert 'abcy' == 'abcx'
E       AssertionError

tests/helpers.py:258: AssertionError
======================================================= 2 failed in 0.24 seconds ========================================================

作为解决方法，我使用断言输出了额外的信息，但输出看起来仍然很奇怪，并使代码崩溃。关于如何在帮助程序文件中激活 pytest 断言自省(introspection)的任何想法？

我找到了一个 different, but related question不幸的是，到目前为止我无法使解决方案起作用:

import pytest
from .helpers import my_helper
pytest.register_assert_rewrite('helpers.my_helper')

Answer 1

我必须像这样将 register_assert_rewrite 放入 tests/__init__.py 中:

import pytest

# we want to have pytest assert introspection in the helpers
pytest.register_assert_rewrite('tests.helpers')