feat(gnolang): increase test coverage from 33% to 70%

[harry-hov]

WIP

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.67%. Comparing base (0ba95bf) to head (3aba945).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1995      +/-   ##
==========================================
+ Coverage   46.25%   46.67%   +0.42%     
==========================================
  Files         483      492       +9     
  Lines       68837    70017    +1180     
==========================================
+ Hits        31838    32681     +843     
- Misses      34368    34620     +252     
- Partials     2631     2716      +85     

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