I often use Nose, Tox or Unittest when testing my python code, specially when it has to be integrated with other modules or other pieces of code. However, now that I've found myself using R more than python for ML modelling and development. I realized that I don't really test my R code (And more importantly I really don't know how to do it well). So my question is, what are good packages that allow you to test R code in a similar manner as Nose, Tox or Unittest do in Python. Additional references such as tutorials will be greatly appreciated as well.
Bonus points for packages in R similar to