I'm not new to programming and I've even worked with some low level C and ASM on AVR, but I really can't get my head around a larger-scale embedded C project.

Being degenerated by the Ruby's philosophy of TDD/BDD, I'm unable to understand how people write and test code like this. I'm not saying it's a bad code, I just don't understand how this can work.

I wanted to get more into some low level programming, but I really have no idea how to approach this, since it looks like a completely different mindset that I'm used to. I don't have trouble understanding pointer arithmetics, or how allocating memory works, but when I see how complex C/C++ code looks compared to Ruby, it just seems impossibly hard.

Since I already ordered myself an Arduino board, I'd love to get more into some low level C and really understand how to do things properly, but it seems like none of the rules of high level languages apply.

Is it even possible to do TDD on embedded devices or when developing drivers or things like custom bootloader, etc.?