Small example to show how to test multiple DSLs with Xtext

MultiLangInjectorProvider.xtend

class MultiLangInjectorProvider extends MyDslInjectorProvider {
	override protected internalCreateInjector() {
		// trigger injector creation of other language
		new SecondDslInjectorProvider().getInjector
		return super.internalCreateInjector()
	}
}

MultiLangTest.xtend

@Test def void successfulLanguageTest() {
	val resourceSet = resourceSetProvider.get
	
	// create a resource for language 'MyDsl'
	val firstLang = resourceSet.createResource(URI.createURI("sample.mydsl"))
	// parse some contents
	firstLang.load(new StringInputStream(".."), emptyMap)
	// and read the root instance
	val root = firstLang.contents.head as MyDslRoot
	// ensure it's not null
	assertNotNull(root)
	// and valid
	validationTester.assertNoIssues(root)
	
	// use the parse helper to read the model under test
	// into the same resource set
	val testMe = parseHelper.parse("..", resourceSet)
	// it's not null, too
	assertNotNull(testMe)
	// and also valid		
	validationTester.assertNoIssues(testMe)
	// more assertions below
	..
}

UnitTest.xtend

@RunWith(XtextRunner)
@InjectWith(MyDSLInjectorProvider)
class MyTest {
	// Helper to read models
	@Inject ParseHelper<MyModel> parseHelper
	// Helper to test all validation rules and ensure resolved links
	@Inject ValidationTestHelper validationTester
	
	@Test def void myTest() {
		val model = parseHelper.parse('Hello World!')
		validationTester.assertNoIssues(model)
	}
}