Write unit tests for v2

[Yang-33]

The implementation of v2 is based on an internal checklist, but there are no tests for almost all of them. While it's not impossible for someone other than the author to manually check it, changes added later can alter the behavior of existing code, making it less meaningful. Please write tests to facilitate easy maintenance and release.

[Yang-33]

It's almost done, but there's still a little more to go... 😄

[Yang-33]

The last one is to detect(not resolve at first) #379 .