> Build the whole thing badly. It doesn't have necessarily to be poorly written code though - you can start with lots of constant functions and later replace w

> Build the whole thing badly. It doesn't have necessarily to be poorly written code though - you can start with lots of constant functions and later replace with actual logic, and still, at each iteration you'll have a complete testable flow. Some test frameworks like Clojure's midje [1] and Python's mock [2] help a lot with this by making mocking functions inside the test painless, so you can start with what you wish you had and then fill the blanks. I believe someone on the internet named this "Wishful Thinking Driven Development", quite ingenious. [1] https://github.com/marick/Midje https://github.com/marick/Midje [2] https://docs.python.org/dev/library/unittest.mock.html#the-patchers https://docs.python.org/dev/library/unittest.mock.html#the-p...