You still write tests in any non-trivial Clojure codebase, and you still probably do REPL-based development for some parts of that project. And if you're doing

You still write tests in any non-trivial Clojure codebase, and you still probably do REPL-based development for some parts of that project. And if you're doing both of those things above, then you almost certainly run some or all of your tests WHILE doing REPL-based development from your always-on REPL. In fact, that's one of the best ways since you don't suffer the JVM startup cost.