enhance ConsistentHashLoadBalance ut

[lixiaojiee]

What is the purpose of the change

enhance ConsistentHashLoadBalance ut

Brief changelog

/dubbo-cluster/src/test/java/org/apache/dubbo/rpc/cluster/loadbalance/ConsistentHashLoadBalanceTest.java
/dubbo-cluster/src/test/java/org/apache/dubbo/rpc/cluster/loadbalance/LoadBalanceBaseTest.java

Verifying this change

ut pass

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[codecov-io]

Codecov Report

Merging #2947 into master will increase coverage by 0.25%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2947      +/-   ##
==========================================
+ Coverage   63.91%   64.17%   +0.25%     
==========================================
  Files         584      584              
  Lines       26056    26056              
  Branches     4563     4563              
==========================================
+ Hits        16654    16721      +67     
+ Misses       7224     7155      -69     
- Partials     2178     2180       +2

Impacted Files	Coverage Δ
...dubbo/rpc/protocol/dubbo/CallbackServiceCodec.java	77.2% <0%> (-2.21%)	⬇️
...apache/dubbo/rpc/protocol/dubbo/DubboProtocol.java	65.83% <0%> (-0.84%)	⬇️
...pache/dubbo/registry/support/AbstractRegistry.java	81.2% <0%> (-0.76%)	⬇️
...dubbo/remoting/exchange/support/DefaultFuture.java	67.78% <0%> (+0.67%)	⬆️
...bo/remoting/transport/netty/NettyCodecAdapter.java	54.68% <0%> (+1.56%)	⬆️
...a/org/apache/dubbo/monitor/dubbo/DubboMonitor.java	89.71% <0%> (+1.86%)	⬆️
...pache/dubbo/remoting/transport/AbstractServer.java	47.91% <0%> (+3.12%)	⬆️
...org/apache/dubbo/rpc/protocol/AbstractInvoker.java	66.12% <0%> (+3.22%)	⬆️
...ng/exchange/support/header/HeartbeatTimerTask.java	78.94% <0%> (+5.26%)	⬆️
...ubbo/rpc/protocol/dubbo/ChannelWrappedInvoker.java	50% <0%> (+8.33%)	⬆️
... and 5 more

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[khanimteyaz]

@lixiaojiee
Sorry for asking this. As I am new here so for the shake of my interest, would it be possible for you to provide some details about the UT, what scenarios it is covering and what was missing earlier? Appreciate your consideration,

[khanimteyaz]

@lixiaojiee
Sorry for asking this. As I am new here so for the shake of my interest, would it be possible for you to provide some details about the UT, what scenarios it is covering and what was missing earlier? Appreciate your consideration,

I think in this PR you are fixing the null pointer exception issue while calling getArgument of mocked invocation object in UT, because it was not mocked. Is this understanding of mine is correct?

[lixiaojiee]

@khanimteyaz There are two reasons why I changed this ut：
1、Fix the null pointer exception
2、I found that the previous test cases were judged on the basis of the average value, which was obviously not reasonable for consistent hash loadbalance