Testing a DSL / Grammar Written With Xtext

Question

I've been set a task of writing a grammar / DSL with XText. It seems reasonably simple. I've been asked to incrementally add rules to the grammar as per a specification. I want to be able to test each new rule that I create.

I have Spring Tool Suite Version: 3.9.2.RELEASE, Build Id: 201712210947, Platform: Eclipse Oxygen.2 (4.7.2).

I've seen textboxes in web browsers that show syntax highlighting based on the validity of the input as per the grammar rules. Also, I'm aware that unit testing is a possibility.

What's the simplest way, minimal fuss, of verifying that the grammar works as expected?

Your help is greatly appreciated.

Thanks in advance,

Ryan

Answer 1

Writing a bunch of unit tests using ParseHelper and ValidationTestHelper should be the most sustainable way to do this.

eg https://github.com/eclipse/xtext-eclipse/blob/master/org.eclipse.xtext.xtext.ui.examples/projects/domainmodel/org.eclipse.xtext.example.domainmodel.tests/src/org/eclipse/xtext/example/domainmodel/tests/ValidationTests.xtend

Answer 2

The answer depends on what you mean by 'verifying that the grammar works as expected'. As Christian noted, unit tests using ParseHelper and ValidationTestHelper will tell you if your grammar is being parsed into the correct model and generating the appropriate errors otherwise. If however you want to test things like content assist, syntax higlighting and such, you have to go a little further and write some tests using AbstactEditorTest, AbstractOutlineTest, etc. in the ui.tests package for your Xtext project. After looking at a lot of tutorials I finally went ahead and bought Lorenzo Bettini's book:

Implementing Domain-Specific Languages with Xtext and Xtend - Second Edition

It was a great help in understanding Xtext, and how to test a grammar as you create it.