• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.8
• Operating System version: deepin 15.11
• Java version: 1.8.0_261

Steps to reproduce this issue

no step

Pls. provide [GitHub address] to reproduce this issue.

Involved documents

1.dubbo-common/src/test/java/org/apache/dubbo/common/config/configcenter/ConfigChangedEventTest.java
2.dubbo-config-spring/src/test/java/org/apache/dubbo/config/spring/registry/MockRegistryFactory.java

Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

Just put your stack trace here!