Add unit tests

[soininen]

No functional changes intended.

These tests may help to prevent breaking backwards compatibility in PR #539

No associated issue.

Checklist before merging

• Documentation (also in Toolbox repo) is up-to-date
• Release notes have been updated
• Unit tests have been added/updated accordingly
• Code has been formatted by black & isort
• Unit tests pass (Toolbox execution tests are being fixed in PR Restore returning multiple parameter values for alternatives filter #562)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.56%. Comparing base (2f8654b) to head (1c9fa0f).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #563      +/-   ##
==========================================
+ Coverage   84.35%   84.56%   +0.20%     
==========================================
  Files          80       80              
  Lines       10887    10890       +3     
  Branches     1599     1599              
==========================================
+ Hits         9184     9209      +25     
+ Misses       1334     1317      -17     
+ Partials      369      364       -5     

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