I have a question to the functional gurus out there:

Do you use unit testing in a functional programming context?

The reason I ask is that programming with a REPL fundamentally changes how you typically write programs - the bottom-up mentality. You don't even write a test-first, you test first! The tested program is then assembled into a unit. I feel there's much less incentive to write a test, if you use a statically typed language and use a REPL as it is meant to. Am I wrong in my thinking?