Add unit tests to cmd/test-cli

[MCarlomagno]

📝 Summary

Adding very simple unit tests (that didn't require any refactor) for cmd/test-cli/beacon.go.

⛱ Motivation and Context

Lack of unit tests under cmd/test-cli/.
Ideally, I would like to work towards some kind of refactor in order to add more tests to the rest of scripts under this folder, by creating injected dependencies and mocking them.

📚 References

#577

✅ I have run these commands

• make lint
• make test
• make test-race
• go mod tidy

[codecov-commenter]

Codecov Report

Merging #578 (f174c47) into develop (190d459) will decrease coverage by 17.03%.
The diff coverage is n/a.

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@@             Coverage Diff              @@
##           develop     #578       +/-   ##
============================================
- Coverage    69.69%   52.66%   -17.03%     
============================================
  Files            7       12        +5     
  Lines         1102     1462      +360     
============================================
+ Hits           768      770        +2     
- Misses         288      644      +356     
- Partials        46       48        +2     

Flag	Coverage Δ
unittests	52.66% <ø> (-17.03%)	⬇️

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see 6 files with indirect coverage changes

[metachris]

What's the goal of the test you've added here?