added first ArchUnit test

build.gradle.kts

@@ -151,6 +151,7 @@ configure(javaProjects) {
 
     dependencies {
         testImplementation("org.junit.jupiter:junit-jupiter:5.5.1")
+        testImplementation("com.tngtech.archunit:archunit-junit5:0.13.1")
     }
 
     tasks.test {

src/test/java/com/beanit/openiec61850/integrationtests/ArchitectureTest.java

@@ -0,0 +1,20 @@
+package com.beanit.openiec61850.integrationtests;
+
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.classes;
+
+import com.tngtech.archunit.junit.AnalyzeClasses;
+import com.tngtech.archunit.junit.ArchTest;
+import com.tngtech.archunit.lang.ArchRule;
+
+@AnalyzeClasses(packages = "com.beanit")
+public class ArchitectureTest {
+
+  @ArchTest
+  public static final ArchRule only_josistack_accesses_its_internal_pkg =
+      classes()
+          .that()
+          .resideInAPackage("..josistack.internal..")
+          .should()
+          .onlyBeAccessed()
+          .byAnyPackage("..josistack..");
+}