Test for GetActiveValidators

[phamminh0811]

1. Summary

Fixes #617

2.Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

3. Implementation details

4. How to test/use

5. Checklist

• Does the Readme need to be updated?

6. Limitations (optional)

7. Future Work (optional)

[codecov]

Codecov Report

Merging #675 (d72c8f3) into main (1ed5da2) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #675      +/-   ##
==========================================
+ Coverage   13.67%   13.68%   +0.01%     
==========================================
  Files         243      243              
  Lines       63047    63047              
==========================================
+ Hits         8620     8628       +8     
+ Misses      53724    53716       -8     
  Partials      703      703              

Flag	Coverage Δ
unittests	13.68% <ø> (+0.01%)	⬆️

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see 1 file with indirect coverage changes

[joe-bowman]

lgtm

[phamminh0811]

@ThanhNhann could you check this pr for me so that we can merge it

[joe-bowman]

lgtm