Great article! I've found myself going through the same cycle of getting something working in the REPL and then regretting not having tests some time in the fut

Great article! I've found myself going through the same cycle of getting something working in the REPL and then regretting not having tests some time in the future several times! In my experience much of the value of unit tests comes from "proofs of correctness", which REPL-driven development also provides! But unit tests also provide a lot of value in making confidence in changes, and knowing that the behaviour your verified in your REPL stays correct weeks and months later.