Sphinx 8.2.0: Tests broken when using sphinx.testsing.path

[attakei]

Describe the bug

Hi, I develop Sphinx extension (e.g. sphinx-revealjs).

When I run tests using sphinx.testing.path for rootdir of fixtures with Sphinx 8.2.0,
all tests raise error unexpected timing.

Expected

Dsiplay RemovedInSphinx90Warning, but test passes.

Actually

All tests fail with AttributeError: 'path' object has no attribute 'is_dir'.

• https://github.com/attakei/sphinx-revealjs/actions/runs/13457324587/job/37604091737

Comment

All tests of Sphinx are written expected that uses pathlib.Path for path-type object and sphinx.testing.fixtures does not care possibility cases using sphinx.testing.path.

It should keep compatibily before release Sphinx 9.x because sphinx.testing.path is but marked deprecated and not removed.

How to Reproduce

I created GitHub repo for reproduction.

git clone http://github.com/attakei-sandbox/sphinx-issue-demo
cd sphinx-issue-demo
pip install .
pytest

Environment Information

Platform:              linux; (Linux-6.13.1-arch2-1-x86_64-with-glibc2.41)
Python version:        3.11.11 (main, Feb 12 2025, 14:51:05) [Clang 19.1.6 ])
Python implementation: CPython
Sphinx version:        8.2.0
Docutils version:      0.21.2
Jinja2 version:        3.1.5
Pygments version:      2.19.1

Sphinx extensions

No extensions (this report is for `sphinx.testing`)

Additional context

No response