Do not write to CWD in tests

[lamontj]

The source tree may be read-only during the build. Use a temporary directory for tests that need to modify the file system.

[Colecf]

For context, we've started using pogreb in the android build system, where source code is read-only during the build.

[lamontj]

Test failures fixed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.49%. Comparing base (76e9512) to head (4bcfc97).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #74   +/-   ##
=======================================
  Coverage   77.49%   77.49%           
=======================================
  Files          25       25           
  Lines        1804     1804           
=======================================
  Hits         1398     1398           
  Misses        281      281           
  Partials      125      125           

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[akrylysov]

Thanks for the contribution! I pushed a commit with a slightly different approach that should automatically work for all future tests. It wraps the file systems used in tests with the Sub file system rooted in a temporary directory. Please let me know if it works for you 59b5287

[colincross]

Yes, 59b5287 works in our read-only tree. Thanks for the patch!

[akrylysov]

Thanks for confirming! I just merged my change to main, and I'm closing this PR.