Lately been thinking about tests primarly in two categories: scaffolding vs structural. Some of my TDD tests are just scaffolding--they are for my verification while building, intended to be thrown away later. Others are important structural tests, and they will remain. twitter.com/redrapids/status/1453724820177182720
Scaffolding tests can be used also to test assumptions about how current code is working, to fix bugs, work in legacy code, and then they can be thrown away as well.
Too many folks come to loathe TDD because they keep all their tests as eternal baggage.
Automate the tests you are running, as long as you would do the manual tests.
Important note: manual != UI tests. Like, if you had a REPL would you test this in there? If so, automate it.