fix: Failing tests on CI

[tuliomir]

This PR aims to fix minor bugs on the CI tests before upgrading to NodeJS 20 on #635 :

After upgrading to NodeJS 20, the mineTransaction.test.ts unit tests started failing. This was due to a stricter policy by Node of crashing whenever there is an unhandled promise in the application, instead of just emitting a warning as it was on NodeJS 14.

Acceptance Criteria

• Promises on MineTransaction tests should always be handled
• The CI must be passing for all PRs

Security Checklist

• Make sure you do not include new dependencies in the project unless strictly necessary and do not include dev-dependencies as production ones. More dependencies increase the possibility of one of them being hijacked and affecting us.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.48%. Comparing base (2169306) to head (32e43e3).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #641       +/-   ##
===========================================
+ Coverage   62.01%   79.48%   +17.47%     
===========================================
  Files          77       77               
  Lines        5826     5826               
  Branches     1223     1210       -13     
===========================================
+ Hits         3613     4631     +1018     
+ Misses       2116     1178      -938     
+ Partials       97       17       -80     

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