introduce archUnit

backend/pom.xml

@@ -43,6 +43,12 @@
             <groupId>org.flywaydb</groupId>
             <artifactId>flyway-core</artifactId>
         </dependency>
+        <dependency>
+            <groupId>com.tngtech.archunit</groupId>
+            <artifactId>archunit</artifactId>
+            <version>1.2.1</version>
+            <scope>test</scope>
+        </dependency>
         <dependency>
             <groupId>org.apache.activemq</groupId>
             <artifactId>artemis-server</artifactId>

backend/src/test/java/com/github/binpastes/paste/api/ArchitectureTest.java

@@ -0,0 +1,50 @@
+package com.github.binpastes.paste.api;
+
+import com.github.binpastes.paste.domain.Paste;
+import com.tngtech.archunit.core.importer.ClassFileImporter;
+import com.tngtech.archunit.core.importer.ImportOption;
+import org.junit.jupiter.api.Test;
+import org.springframework.stereotype.Repository;
+
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noClasses;
+import static com.tngtech.archunit.lang.syntax.ArchRuleDefinition.noMethods;
+
+class ArchitectureTest {
+
+    private static final ImportOption DO_NOT_INCLUDE_MAVEN_TESTS = location -> !location.contains("/test-classes/");
+
+    @Test
+    void domainClassNeverRendered() {
+        var importedClasses = new ClassFileImporter()
+                .withImportOption(DO_NOT_INCLUDE_MAVEN_TESTS)
+                .withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_JARS)
+                .withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_TESTS)
+                .importPackages("com.github.binpastes.paste.api");
+
+        var rule = noMethods()
+                .that()
+                .areDeclaredInClassesThat()
+                .resideInAPackage("com.github.binpastes.paste.api")
+                .should()
+                .haveRawReturnType(Paste.class);
+
+        rule.check(importedClasses);
+    }
+
+    @Test
+    void injectionsMindArchitecturalBorders() {
+        var importedClasses = new ClassFileImporter()
+                .withImportOption(DO_NOT_INCLUDE_MAVEN_TESTS)
+                .withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_JARS)
+                .withImportOption(ImportOption.Predefined.DO_NOT_INCLUDE_TESTS)
+                .importPackages("com.github.binpastes.paste.api");
+
+        var rule = noClasses()
+                .that()
+                .resideInAPackage("com.github.binpastes.paste.api")
+                .should()
+                .dependOnClassesThat().areAnnotatedWith(Repository.class);
+
+        rule.check(importedClasses);
+    }
+}