It's closer to a repl with save state and replay. A repl will get the code working faster than tests but doesn't easily allow rechecking the same stuff later when things change (either your code or the users of it). I haven't seen a repl with save&replay but that might be a really efficient way to write the unit tests.
You just copy-and-paste the relevant input-output and there is your test. There isn't a need for any extra tools when using the REPL to come up with regression tests (obviously a REPL cannot be used to do TDD).
