Feature Toggles are a nice way to hide and/or handle partially finished functionalities in production environments. This may sound weird for those deploying code to production on demand, but it is quite common to find this situation when practicing continuous integration, delivery, or deployment.

We have introduced the technique and discussed the pros and cons. We have also enumerated some of the typical cases where toggling features can be helpful. Finally, we have implemented two different use cases: a Feature Toggle with a very simple REST API, and a Feature Toggle in a web application.

Although the code presented in this chapter is fully functional, it isn't very common to use a file-based property system for this matter. There are many libraries more suitable for production environments that can help us to implement this technique, providing a lot of capabilities, such as using a web interface to handle features, storing preferences in a database, or allowing access to concrete user profiles.

In the next chapter we are going to put the TDD concepts described in the book all together. We are going to name some good practices and recommendations that are very useful when programming in the TDD way.