Unit tests for operator crate

[killme2008]

What type of enhancement is this?

Tech debt reduction

What does the enhancement do?

The operator crate serves as the primary interface for all protocols, including SQL and gRPC. It plays a crucial role in connecting different database components and processing SQL statements and gRPC requests from higher layers.

However, it appears to have a relatively low number of unit test cases, which could be improved by adding more tests.

Implementation challenges

No response