[ISSUE #8345] add some tests for nameserver

[TanXiang7o]

Fixes #8345

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.47%. Comparing base (6f77f05) to head (41f798f).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #8349      +/-   ##
=============================================
+ Coverage      44.36%   44.47%   +0.10%     
- Complexity     10782    10811      +29     
=============================================
  Files           1274     1274              
  Lines          88951    88951              
  Branches       11433    11433              
=============================================
+ Hits           39463    39559      +96     
+ Misses         44535    44424     -111     
- Partials        4953     4968      +15     

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[ShannonDing]

link #8262