refactor DubboAppenderTest

[cheese8]

What is the purpose of the change

#10212

[codecov-commenter]

Codecov Report

Merging #10250 (8df989d) into 3.0 (d6a1ff4) will decrease coverage by 0.10%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                3.0   #10250      +/-   ##
============================================
- Coverage     65.66%   65.55%   -0.11%     
- Complexity      296      318      +22     
============================================
  Files          1233     1233              
  Lines         53677    53677              
  Branches       8098     8099       +1     
============================================
- Hits          35247    35188      -59     
- Misses        14609    14654      +45     
- Partials       3821     3835      +14     

Impacted Files	Coverage Δ
...dubbo/common/status/support/LoadStatusChecker.java	41.66% <0.00%> (-25.00%)	⬇️
.../remoting/api/SingleProtocolConnectionManager.java	61.53% <0.00%> (-23.08%)	⬇️
...nt/metadata/ServiceInstanceHostPortCustomizer.java	65.78% <0.00%> (-21.06%)	⬇️
...che/dubbo/registry/client/NopServiceDiscovery.java	44.44% <0.00%> (-11.12%)	⬇️
...mmon/threadpool/support/AbortPolicyWithReport.java	73.68% <0.00%> (-10.53%)	⬇️
.../common/threadpool/serial/SerializingExecutor.java	70.37% <0.00%> (-7.41%)	⬇️
...he/dubbo/remoting/transport/netty/NettyHelper.java	29.03% <0.00%> (-6.46%)	⬇️
...ava/org/apache/dubbo/rpc/proxy/InvocationUtil.java	84.84% <0.00%> (-6.07%)	⬇️
...e/dubbo/rpc/protocol/tri/transport/WriteQueue.java	73.80% <0.00%> (-4.77%)	⬇️
...ubbo/common/system/OperatingSystemBeanManager.java	50.00% <0.00%> (-4.55%)	⬇️
... and 20 more

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