I would generally say the same thing, but most of the experimentation I do in the REPL is "is this crazy thing possible", not "is f(4) = 3.23432198"?

And sometimes it's just not worth testing, because it's something like ``hmm, I wonder if 'intercalate ", " ["foo", "bar", "baz"]' returns 'foo, bar, baz'; ahh yes, it does.'' The only reason to test that is because you want your test suite to run slower.