[#1731] Updating the Unit Testing section of the Xtext website.

Signed-off-by: Tamas Miklossy <miklossy@itemis.de>

xtext-website/documentation/303_runtime_concepts.md

@@ -740,7 +740,7 @@ import org.example.domainmodel.DomainmodelInjectorProvider
 @InjectWith(DomainmodelInjectorProvider)
 @RunWith(XtextRunner)
 class ParserTest {
-    @Test void simple() {
+    @Test def void simple() {
         assertTrue(true)
     }
 }
@@ -753,15 +753,15 @@ A test class for JUnit 5 looks quite similar. Instead of runners JUnit 5 has a n
 ```xtend
 import org.eclipse.xtext.testing.InjectWith
 import org.eclipse.xtext.testing.extensions.InjectionExtension
-import org.junit.jupiter.api.extension.ExtendWith
+import org.junit.jupiter.api.^extension.ExtendWith
 import org.junit.jupiter.api.Test
 import static org.junit.jupiter.api.Assertions.*
 import org.example.domainmodel.DomainmodelInjectorProvider
 
 @InjectWith(DomainmodelInjectorProvider)
 @ExtendWith(InjectionExtension)
 class ParserTest {
-    @Test void simple() {
+    @Test def void simple() {
         assertTrue(true)
     }
 }
@@ -789,7 +789,7 @@ def void parseDomainmodel() {
 }
 ```
 
-### Testing Validators {#test-validators}
+### Testing the Validator {#test-validators}
 
 Testing your validation is very simple with the [ValidationTestHelper]({{site.src.xtext_core}}/org.eclipse.xtext.testing/src/org/eclipse/xtext/testing/validation/ValidationTestHelper.java):
 
@@ -850,6 +850,8 @@ public class MyLanguageStandaloneSetup extends MyLanguageStandaloneSetupGenerate
 
 This only applies to referencing dependencies to imported Ecore models and languages based on them which may be used in the test. The inherited dependencies from mixed-in grammars are automatically listed in the generated super class already, and nothing needs to be done for those.
 
+The Xtext example projects (*File &rarr; New &rarr; Example &rarr; Xtext Examples*) contain further unit test cases, e.g. testing the formatter, serializer, compiler, ...etc . Feel free to study the corresponding `org.eclipse.xtext.example.<language>.tests` projects to get some inspirations on how to implement automated unit test cases for your Xtext-based language.
+
 ---
 
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