[nailer]

Similar here. I pick the one thing the system depends on, I call it ‘hello world’, and implement it with no UI at all and one command line test. The test exists to prove to myself and my team that it works, and know when it breaks, not to demonstrate an API. You can call it TDD or not.

So I when someone suggests “we can build X” I say yes but first we need to build “hello world”. The discussion about what constitutes Hello World is often valuable, but often ends up with examples like the article, eg "can we write a message and the recipient gets it?" "can we do one trade?" etc. These sometimes seems like trivial goals but implementing them can be surprising.