test: prepare test sources for strict mode

[Shinigami92]

extracted #2102

[codecov]

Codecov Report

Merging #2107 (d304773) into next (1cadfb9) will decrease coverage by 0.02%.
The diff coverage is n/a.

❗ Current head d304773 differs from pull request most recent head d1da1f6. Consider uploading reports for the commit d1da1f6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #2107      +/-   ##
==========================================
- Coverage   99.60%   99.58%   -0.02%     
==========================================
  Files        2605     2567      -38     
  Lines      244944   243371    -1573     
  Branches     1254     1243      -11     
==========================================
- Hits       243967   242352    -1615     
- Misses        950      992      +42     
  Partials       27       27              

see 71 files with indirect coverage changes

[ST-DDT]

Please amend the title or description to include at least the intention of this PR before merging this.
So we are inclusive to our community that wasn't present in our private conversation where we talked about this change.

E.g. This fixes some issues preventing the use of strict for our test sources
or prepare test sources for strict mode