Potentially. But, as with all things, there's "the way you could do things" and "the way you should do things". Just because you can do manual testing doesn't m

Potentially. But, as with all things, there's "the way you could do things" and "the way you should do things". Just because you can do manual testing doesn't mean you should avoid automated testing. It MAY be useful to do some manual exploration to find suitable test cases, but once found, they should totally be conserved in source. It may also be faster to find an issue in the REPL, using various tracing tools ("hm, this function returns the wrong thing when I feed it X, let us enable tracing on a few things and see if anything stands out", followed by "aha, that other function over there is actually the problem, let me add some test cases, so we don't have a regression there"). None of these are impossible without a REPL, but may require extensive modification of the source and a recompilation to get the same effect (followed, probably, by either converting your tracing to debug logs, guarded by a verbosity flag, or by painstakingly track down each print and rip it out again).