Add internal tests and fix some bugs

[shamaton]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 90.47619% with 6 lines in your changes missing coverage. Please review.

Project coverage is 98.09%. Comparing base (d1c8383) to head (aaf2f86).
Report is 42 commits behind head on master.

Files	Patch %	Lines
internal/encoding/encoding.go	20.00%	4 Missing ⚠️
internal/encoding/struct.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master      #39       +/-   ##
===========================================
+ Coverage   70.43%   98.09%   +27.65%     
===========================================
  Files          72       72               
  Lines        5547     5554        +7     
===========================================
+ Hits         3907     5448     +1541     
+ Misses        999       82      -917     
+ Partials      641       24      -617     

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