tests: Include tests in coverage metric

[l0b0]

Missing coverage in tests means unreached (and usually unreachable) test
code, often indicating a test bug.

Related Issue(s): #331

Description:

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• Documentation has been updated to reflect changes, if applicable
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #493 (3e5fed6) into main (f9573f8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #493   +/-   ##
=======================================
  Coverage   91.66%   91.66%           
=======================================
  Files          40       40           
  Lines        5245     5245           
=======================================
  Hits         4808     4808           
  Misses        437      437           

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