$ python -m pytest test_issue.py
======================== test session starts =========================
platform darwin -- Python 3.13.7, pytest-9.0.2, pluggy-1.6.0
rootdir: /Users/carlos/workspace/tmp/delme
collected 1 item

test_issue.py .                                                [100%]

========================== warnings summary ==========================
test_issue.py:3
  /Users/carlos/workspace/tmp/delme/test_issue.py:3: PytestCollectionWarning: cannot collect test class 'TestWindow' because it has a __init__ constructor (from: test_issue.py)
    class TestWindow(tk.Tk):

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
==================== 1 passed, 1 warning in 0.19s ====================

$ python -m pip freeze > requirements.txt

$ uvx --python=3.14.2 --with-requirements=requirements.txt python -m pytest test_issue.py
====================================== test session starts ======================================
platform darwin -- Python 3.14.2, pytest-9.0.2, pluggy-1.6.0
rootdir: /Users/carlos/workspace/tmp/delme
collected 1 item

test_issue.py F                                                                           [100%]

=========================================== FAILURES ============================================
__________________________________________ test_window __________________________________________

    def test_window():
>       app = TestWindow()
              ^^^^^^^^^^^^

test_issue.py:7:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <test_issue.TestWindow object .>, screenName = None, baseName = '__main__'
className = 'Tk', useTk = True, sync = False, use = None

    def __init__(self, screenName=None, baseName=None, className='Tk',
                 useTk=True, sync=False, use=None):
        """Return a new top level widget on screen SCREENNAME. A new Tcl interpreter will
        be created. BASENAME will be used for the identification of the profile file (see
        readprofile).
        It is constructed from sys.argv[0] without extensions if None is given. CLASSNAME
        is the name of the widget class."""
        self.master = None
        self.children = {}
        self._tkloaded = False
        # to avoid recursions in the getattr code in case of failure, we
        # ensure that self.tk is always _something_.
        self.tk = None
        if baseName is None:
            import os
            baseName = os.path.basename(sys.argv[0])
            baseName, ext = os.path.splitext(baseName)
            if ext not in ('.py', '.pyc'):
                baseName = baseName + ext
        interactive = False
>       self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
E       _tkinter.TclError: Can't find a usable init.tcl in the following directories:
E           /tools/deps/lib/tcl8.6 /Users/carlos/.cache/uv/archive-v0/KRJC-IU7K_S7tTfnyEv1J/lib/tcl8.6 /Users/carlos/.cache/uv/archive-v0/lib/tcl8.6 /Users/carlos/.cache/uv/archive-v0/KRJC-IU7K_S7tTfnyEv1J/library /Users/carlos/.cache/uv/archive-v0/library /Users/carlos/.cache/uv/archive-v0/tcl8.6.14/library /Users/carlos/.cache/uv/tcl8.6.14/library
E
E
E
E       This probably means that Tcl wasn't installed properly.

../../../.local/share/uv/python/cpython-3.14.2-macos-aarch64-none/lib/python3.14/tkinter/__init__.py:2479: TclError
======================================= warnings summary ========================================
test_issue.py:3
  /Users/carlos/workspace/tmp/delme/test_issue.py:3: PytestCollectionWarning: cannot collect test class 'TestWindow' because it has a __init__ constructor (from: test_issue.py)
    class TestWindow(tk.Tk):

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
==================================== short test summary info ====================================
FAILED test_issue.py::test_window - _tkinter.TclError: Can't find a usable init.tcl in the following directories:
================================= 1 failed, 1 warning in 0.14s ==================================