unit test

[sunbufu]

Hi, this PR commit 2 files for unit test.

• CoderUtilTest
• RegistryServerSyncTest

[codecov-io]

Codecov Report

Merging #268 into develop will increase coverage by 0.4%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             develop     #268     +/-   ##
============================================
+ Coverage      21.58%   21.99%   +0.4%     
- Complexity       295      305     +10     
============================================
  Files             85       85             
  Lines           3456     3456             
  Branches         547      547             
============================================
+ Hits             746      760     +14     
+ Misses          2628     2613     -15     
- Partials          82       83      +1

Impacted Files	Coverage Δ	Complexity Δ
...apache/dubbo/admin/service/RegistryServerSync.java	94.02% <0%> (+4.47%)	24% <0%> (+4%)	⬆️
.../java/org/apache/dubbo/admin/common/util/Tool.java	26.31% <0%> (+10.52%)	2% <0%> (+1%)	⬆️
.../org/apache/dubbo/admin/common/util/CoderUtil.java	83.33% <0%> (+30%)	10% <0%> (+5%)	⬆️

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