I recall @pradyunsg made the observation under a PR, but I can’t locate it now. (Edit: Found it #9017 (comment))

The specific failure is

E       AssertionError: temp files not expected
-- created: -------------------
  tmp/com.apple.dyld
          sh-B4B247918EFC62F0DED3F9B92246A6C10C7FECE20649ECEA30D36D86DEF79029.closure  (39976 bytes)
          uname-8487F8338686B8B010BF7BAEFA1A50C27FCA318D2FED3E6B363D8D561583F290.closure  (36168 bytes)

(The list of files change depending on the test case.)

I did some research, it seems like com.apple.dyld is a storage called shared dyld cache and is a cache mechanism used by Apple’s dynamic linker (dyld3). All information I’ve found so far are about iOS, but it shouldn’t be surprising if Apple port that to macOS. This post from 2018 talks about the mechanism in more detail.

I’m not sure why the Azure images use this mechanism (my machine running Catelina doesn’t seem to have them), but it seems like we should be safe to just ignore the whole com.apple.dyld directory when we check for temporary files?