test(contractstaking): add unit tests

[saitofun]

Description

Fixes #4123

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• make test

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.39%. Comparing base (e1f0636) to head (715f0b2).
Report is 177 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4126      +/-   ##
==========================================
+ Coverage   75.38%   76.39%   +1.01%     
==========================================
  Files         303      339      +36     
  Lines       25923    28868    +2945     
==========================================
+ Hits        19541    22053    +2512     
- Misses       5360     5716     +356     
- Partials     1022     1099      +77     

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[sonarcloud]

Quality Gate passed

Issues
3 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud