Increase tests coverage

[asimonok]

Increase tests coverage.
Resolves #45.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +32.53 🎉

Comparison is base (936c8d9) 66.78% compared to head (ee80857) 99.32%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #47       +/-   ##
===========================================
+ Coverage   66.78%   99.32%   +32.53%     
===========================================
  Files          30       30               
  Lines         286      295        +9     
  Branches       35       36        +1     
===========================================
+ Hits          191      293      +102     
+ Misses         89        0       -89     
+ Partials        6        2        -4     

Impacted Files	Coverage Δ
src/constants/tests.ts	100.00% <ø> (ø)
src/components/FieldsEditor/FieldsEditor.tsx	100.00% <100.00%> (+66.66%)	⬆️
src/components/ValueInput/ValueInput.tsx	97.22% <100.00%> (+64.78%)	⬆️
src/components/ValuesEditor/ValuesEditor.tsx	100.00% <100.00%> (+64.86%)	⬆️
src/module.ts	100.00% <100.00%> (ø)
src/utils/frame.ts	100.00% <100.00%> (+41.17%)	⬆️

... and 1 file with indirect coverage changes

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[mikhail-vl]

Looks great!