add some junit test

[chenhao26-nineteen]

Please do not create a Pull Request without creating an issue first.

What is the purpose of the change

Add some JUnit tests

Brief changelog

XX

Verifying this change

XXXX

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a Github issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a Github issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [ISSUE #123] Fix UnknownException when host config not exist. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in test module.
• Run mvn -B clean package apache-rat:check findbugs:findbugs -Dmaven.test.skip=true to make sure basic checks pass. Run mvn clean install -DskipITs to make sure unit-test pass. Run mvn clean test-compile failsafe:integration-test to make sure integration-test pass.

[codecov-commenter]

Codecov Report

Merging #8966 (c7ee5bd) into develop (8f8a1f3) will increase coverage by 0.05%.
The diff coverage is 0.00%.

@@              Coverage Diff              @@
##             develop    #8966      +/-   ##
=============================================
+ Coverage      43.33%   43.39%   +0.05%     
- Complexity      4722     4740      +18     
=============================================
  Files            912      912              
  Lines          32584    32584              
  Branches        3761     3761              
=============================================
+ Hits           14121    14140      +19     
+ Misses         17104    17074      -30     
- Partials        1359     1370      +11     

Impacted Files	Coverage Δ
...ba/nacos/client/naming/core/ServerListManager.java	38.15% <0.00%> (ø)
.../naming/push/v1/NamingSubscriberServiceV1Impl.java	66.66% <0.00%> (-15.88%)	⬇️
...m/alibaba/nacos/naming/misc/HttpClientManager.java	69.04% <0.00%> (-14.29%)	⬇️
...alibaba/nacos/client/config/impl/ClientWorker.java	50.29% <0.00%> (-4.68%)	⬇️
...os/client/auth/ram/identify/CredentialService.java	78.84% <0.00%> (-3.85%)	⬇️
...baba/nacos/naming/healthcheck/HealthCheckTask.java	47.05% <0.00%> (-1.48%)	⬇️
...va/com/alibaba/nacos/naming/misc/SwitchDomain.java	52.22% <0.00%> (-0.56%)	⬇️
...a/com/alibaba/nacos/naming/push/v1/PushClient.java	46.93% <0.00%> (ø)
.../core/v2/event/publisher/NamingEventPublisher.java	76.25% <0.00%> (+1.25%)	⬆️
...m/alibaba/nacos/core/remote/ConnectionManager.java	37.86% <0.00%> (+1.47%)	⬆️
... and 6 more

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