Mittwoch, 24. April 2013

Simple Table DSL in Groovy

Sometimes the best way to model data is as a table. A good example where you could use tables is the spock framework. Spock is a great testing framework for Java and Groovy. In spock the test parameters can be defined as a table. The spock framework use Groovy AST transformations to implement the DSL for the tables. I think about if there is a simpler way to parse an embedded table DSL in groovy. Not with the same features then the spock table DSL. My requirements for the DSL are to define a table and to have support for variables in the table.

Here a short example of such a table:

To implement the DSL parser in groovy I use two groovy languages feature:
  1. The category feature to define the OR operators, for the different types of the table values 
  2. The dynamic of groovy for the variable support, the getProperty is overwritten and creates a object of type Var for a undefined groovy variable
The code below contains a simple groovy implementation of a table DSL parser. The simple parser now can be used to parse the table DSL from the example above. How the DSL can be use in JUnit is show in the parameterized test in the listing below. Not a perfect example, because for testing you should use Spock instead.