Fix slow tests

[akhoubani]

Fixes #46

[codecov[bot]]

Codecov Report

Base: 61.42% // Head: 61.42% // No change to project coverage :thumbsup:

Coverage data is based on head (884416d) compared to base (33c389d). Patch coverage: 0.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #47 +/- ## ======================================= Coverage 61.42% 61.42% ======================================= Files 9 9 Lines 534 534 ======================================= Hits 328 328 Misses 206 206 ``` | [Impacted Files](https://codecov.io/gh/snek5000/snek5000-cbox/pull/47?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=snek5000) | Coverage Δ | | |---|---|---| | [tests/test\_slow\_sidewall.py](https://codecov.io/gh/snek5000/snek5000-cbox/pull/47/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=snek5000#diff-dGVzdHMvdGVzdF9zbG93X3NpZGV3YWxsLnB5) | `12.80% <0.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=snek5000). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=snek5000)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[paugier]

Thank you!