Adding tests for covert.passphrase

[covert-encryption]

No description provided.

[codecov-commenter]

Codecov Report

Merging #48 (164b94e) into main (8468c26) will increase coverage by 3.21%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #48      +/-   ##
==========================================
+ Coverage   45.48%   48.69%   +3.21%     
==========================================
  Files          17       17              
  Lines        1992     1992              
  Branches      452      452              
==========================================
+ Hits          906      970      +64     
+ Misses        977      912      -65     
- Partials      109      110       +1     

Impacted Files	Coverage Δ
covert/elligator.py	82.92% <0.00%> (+1.62%)	⬆️
covert/util.py	74.57% <0.00%> (+1.69%)	⬆️
covert/passphrase.py	56.25% <0.00%> (+42.36%)	⬆️

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