Add architecture test to ensure correct usage of TraceLink class

framework/common/pom.xml

@@ -62,5 +62,10 @@
       <artifactId>sqlite-jdbc</artifactId>
       <version>3.46.0.1</version>
     </dependency>
+    <dependency>
+      <groupId>com.tngtech.archunit</groupId>
+      <artifactId>archunit-junit5</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>

framework/common/src/test/java/edu/kit/kastel/mcse/ardoco/core/TraceLinkArchitectureTest.java

@@ -0,0 +1,30 @@
+package edu.kit.kastel.mcse.ardoco.core;
+
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.methods;
+
+import com.tngtech.archunit.base.DescribedPredicate;
+import com.tngtech.archunit.core.domain.JavaClass;
+import com.tngtech.archunit.junit.AnalyzeClasses;
+import com.tngtech.archunit.junit.ArchTest;
+import com.tngtech.archunit.lang.ArchRule;
+
+import edu.kit.kastel.mcse.ardoco.core.api.tracelink.TraceLink;
+
+@AnalyzeClasses(packages = "edu.kit.kastel.mcse.ardoco")
+class TraceLinkArchitectureTest {
+    private static final DescribedPredicate<JavaClass> isSubclassOfTraceLink = new DescribedPredicate<>("subclass of " + TraceLink.class) {
+        @Override
+        public boolean test(JavaClass clazz) {
+            return clazz.isAssignableTo(TraceLink.class);
+        }
+    };
+
+    @ArchTest
+    static final ArchRule onlyTraceLinkAsReturnType = methods().that()
+            .haveRawReturnType(isSubclassOfTraceLink)
+            .and()
+            .areNotPrivate()
+            .should()
+            .haveRawReturnType(TraceLink.class)
+            .because("the specific subclasses of TraceLink shall not be used as return type in non-private methods");
+}