fix: enhance test coverage

[VineyAT]

Description

• enhance test coverage rate

[codecov]

Codecov Report

Merging #9 (aa7025e) into master (498e3c9) will increase coverage by 2.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master       #9      +/-   ##
==========================================
+ Coverage   88.33%   90.38%   +2.05%     
==========================================
  Files          11       11              
  Lines         540      541       +1     
==========================================
+ Hits          477      489      +12     
+ Misses         35       29       -6     
+ Partials       28       23       -5     

Impacted Files	Coverage Δ
event.go	86.53% <100.00%> (+10.06%)	⬆️
factory.go	100.00% <0.00%> (+2.22%)	⬆️
key.go	100.00% <0.00%> (+22.22%)	⬆️

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