Fix synology_dsm test side effects

[edenhaus]

Breaking change

Proposed change

Fix the side effects introduced by synology_dsm by using patch instead of setting tempdir globally

Before this fix the shell_commands tests would fail as they expect tempdir to be None
Can be reproduced with pytest tests/components/synology_dsm/test_media_source.py tests/components/shell_command/test_init.py
Noticed in https://github.com/home-assistant/core/actions/runs/8535313705/job/23382222724

=================================== FAILURES ===================================
____________________________ test_executing_service ____________________________
[gw0] linux -- Python 3.12.2 /home/runner/work/core/core/venv/bin/python3

hass = <HomeAssistant RUNNING>

    async def test_executing_service(hass: HomeAssistant) -> None:
        """Test if able to call a configured service."""
        with tempfile.TemporaryDirectory() as tempdirname:
>           path = os.path.join(tempdirname, "called.txt")

tests/components/shell_command/test_init.py:37: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
<frozen posixpath>:90: in join
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

funcname = 'join'
args = (b'/tmp/pytest-of-runner/pytest-0/popen-gw0/test_media_view0/tmpgbg9deoo', 'called.txt')
hasstr = True, hasbytes = True, s = 'called.txt'

>   ???
E   TypeError: Can't mix strings and bytes in path components

<frozen genericpath>:167: TypeError

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[home-assistant]

Hey there @hacf-fr, @Quentame, @mib1185, mind taking a look at this pull request as it has been labeled with an integration (synology_dsm) you are listed as a code owner for? Thanks!

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[MartinHjelmare]

This is weird. Does this test actually save a file in a temporary directory? The library should just be patched instead and it's enough to assert that the library is called correctly. And of course we shouldn't create the view directly in the test but use our client to make a request to the server endpoint.

[edenhaus]

The issue was that the test set the tempdir globally with tempfile.tempdir = tmp_path.
As I'm not familiar with the integration I fixed it in the least invasive way, and that was to patch it instead.

[MartinHjelmare]

Sure. This was just a side note.