I suppose that if you do keep things that small, it could work well to trash and rewrite. Plus it has the benefit of making you consider explicitly what is going/staying.

Personally, I like my tests to be pretty clearly about the behavior of the contract, and not the implementation, which is hard when you require every method have a test.

I'd also be concerned that other team members are reluctant to delete tests - as this is a dysfunction I see often, and try to counteract with varying degrees of success.