fix: Potential race for file access in DotTest

[joweich]

It appears like CI runs for DotTest fail non-deterministically. See recent runs of the coverage CI:

• PR-245
• PR-246
• PR-247

While I can't reproduce this locally, my suspicion is that multiple tests use "./test.dot" simultaneously, which then causes race conditions or file access conflicts due to concurrent write/read attempts to the same file path.
This PR provides a fix by making the filenames unique (683ed98).
f826ab6 increases cross-platform compatibility and should be unrelated to this issue.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (4dbde3d) to head (f826ab6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #249   +/-   ##
=======================================
  Coverage   99.59%   99.59%           
=======================================
  Files          56       56           
  Lines        2738     2744    +6     
  Branches      135      135           
=======================================
+ Hits         2727     2733    +6     
  Misses         11       11           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[bobluppes]

Thank you for noticing this and addressing it!!

I am fairly confident that this was indeed a race condition. LGTM 🚀