Need to improve the test coverage on rueidiscompat

[rueian]

Currently, we have poor test coverage on rueidiscompat:

Details of which lines are not covered can be found here: https://app.codecov.io/gh/redis/rueidis/tree/main/rueidiscompat

We hope that we can improve the coverage to be close to 100%.

[mingdaoy]

Hi @rueian, I'd be happy to work on this!

[rueian]

Hi @mingdaoy, thank you! You can just send PRs whenever you make any small improvements to the coverage.