Add some tests

[bjoernricks]

No description provided.

[codecov]

Codecov Report

Merging #4 into master will increase coverage by 1.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master       #4      +/-   ##
==========================================
+ Coverage   12.66%   13.82%   +1.16%     
==========================================
  Files           9        9              
  Lines        1974     1974              
==========================================
+ Hits          250      273      +23     
+ Misses       1724     1701      -23

Impacted Files	Coverage Δ
gvm/utils.py	100% <ø> (+83.33%)	⬆️
gvm/transforms.py	60% <0%> (+60%)	⬆️
gvm/errors.py	100% <0%> (+100%)	⬆️

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