Improved code coverage

[cjs1992-github]

When we tested lettuce's code coverage, we found that some modules had low coverage, and we looked athttps://app.codecov.io/gh/lettuce-io/lettuce-core/At this site, we found that lettuse's code coverage was gradually decreasing,
Can we submit some test cases to increase code coverage? Are there specific rules or requirements, if possible?

[mp911de]

Sure, feel free to do so. If you craft tests, then please for useful things (e.g. testing getters/setters isn't useful on its own).

Thanks a lot!

[tishun]

@cjs1992-github I am closing this issue due to lack of traction.

In the mean time you are more than welcome to submit PRs with tests to help bump up the coverage!