add selfplay test

[huangshiyu13]

Description

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have ensured make test pass (required).
• I have checked the code using make format (required).

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (58c022f) 62.78% compared to head (714a9ec) 66.09%.
Report is 4 commits behind head on main.

Files	Patch %	Lines
openrl/selfplay/callbacks/selfplay_api.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #275      +/-   ##
==========================================
+ Coverage   62.78%   66.09%   +3.30%     
==========================================
  Files         255      252       -3     
  Lines       13466    13156     -310     
==========================================
+ Hits         8455     8695     +240     
+ Misses       5011     4461     -550     

Flag	Coverage Δ
unittests	66.09% <80.00%> (+3.30%)	⬆️

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