In this chapter we introduced unit testing for languages implemented with Xtext. Being able to test most of the DSL aspects without having to start an Eclipse environment really speeds up development.
Test Driven Development is an important programming methodology that helps you make your implementations more modular, more reliable, and resilient to changes of the libraries used by your code.
In the next chapter we will implement a DSL based on expressions; besides the apparent simplicity, parsing and checking expressions is not that trivial, since arithmetic and boolean expressions are inherently recursive, and dealing with recursion always requires some additional attention and effort. We will also implement a type system to check that expressions are well-typed.
