tests: fix CI flaky tests

[pedroferreira1]

Acceptance Criteria

• Include here all things that this PR should solve

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 ✅

Comparison is base (217797f) 64.86% compared to head (4e52796) 78.29%.

Additional details and impacted files

@@             Coverage Diff             @@
##              dev     #585       +/-   ##
===========================================
+ Coverage   64.86%   78.29%   +13.43%     
===========================================
  Files          67       67               
  Lines        5254     5257        +3     
  Branches     1108     1108               
===========================================
+ Hits         3408     4116      +708     
+ Misses       1766     1126      -640     
+ Partials       80       15       -65     

Files	Coverage Δ
src/new/wallet.js	95.63% <100.00%> (+54.82%)	⬆️
src/storage/leveldb/store.ts	92.17% <100.00%> (+4.34%)	⬆️
src/storage/memory_store.ts	96.75% <100.00%> (+6.48%)	⬆️
src/types.ts	33.33% <ø> (ø)

... and 21 files with indirect coverage changes

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[pedroferreira1]

This PR was split into others: #589 and #590