chore(backend): add integration test for PingRepository with Testcontainers setup

- Implemented a minimal integration test to validate persistence layer functionality.
- Configured PostgreSQL Testcontainer and Flyway migrations for testing.
- Added `TestPersistenceConfig` to isolate testing setup and avoid loading unnecessary components.
- Updated build script to include Testcontainers dependencies.

backend/services/ping/ping-service/build.gradle.kts

@@ -42,6 +42,7 @@ dependencies {
 
     // === Testing ===
     testImplementation(libs.bundles.testing.jvm)
+    testImplementation(libs.bundles.testcontainers) // WICHTIG: Testcontainer Bundle hinzugefügt
     testImplementation(libs.spring.boot.starter.test)
     testImplementation(libs.spring.security.test)
 }

backend/services/ping/ping-service/src/test/kotlin/at/mocode/ping/infrastructure/persistence/PingRepositoryTest.kt

@@ -0,0 +1,88 @@
+package at.mocode.ping.infrastructure.persistence
+
+import at.mocode.ping.domain.Ping
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest
+import org.springframework.context.annotation.Import
+import org.springframework.test.context.ActiveProfiles
+import org.springframework.test.context.ContextConfiguration
+import org.springframework.test.context.DynamicPropertyRegistry
+import org.springframework.test.context.DynamicPropertySource
+import org.testcontainers.containers.PostgreSQLContainer
+import org.testcontainers.junit.jupiter.Container
+import org.testcontainers.junit.jupiter.Testcontainers
+import java.time.Instant
+import kotlin.uuid.ExperimentalUuidApi
+import kotlin.uuid.Uuid
+import kotlin.uuid.toJavaUuid
+
+/**
+ * Minimaler Integrationstest für die Persistenz-Schicht.
+ * Prüft:
+ * 1. Startet echte Postgres DB (via Testcontainers).
+ * 2. Führt Flyway-Migrationen aus (Schema-Erstellung).
+ * 3. Speichert und lädt eine Entity (Mapping-Check).
+ */
+@DataJpaTest
+@Testcontainers
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+@ContextConfiguration(classes = [TestPersistenceConfig::class]) // Nutzt isolierte Config statt Main-App
+@Import(PingRepositoryAdapter::class) // Importiert den Adapter, den wir testen wollen
+@ActiveProfiles("test") // WICHTIG: Lädt application-test.yaml
+@OptIn(ExperimentalUuidApi::class)
+class PingRepositoryTest {
+
+    @Autowired
+    private lateinit var repositoryAdapter: PingRepositoryAdapter
+
+    // Wir nutzen das Repository direkt, um zu prüfen, ob JPA funktioniert
+    @Autowired
+    private lateinit var springDataRepository: SpringDataPingRepository
+
+    companion object {
+        @Container
+        val postgres = PostgreSQLContainer("postgres:16-alpine")
+            .withDatabaseName("testdb")
+            .withUsername("test")
+            .withPassword("test")
+
+        @JvmStatic
+        @DynamicPropertySource
+        fun registerPgProperties(registry: DynamicPropertyRegistry) {
+            registry.add("spring.datasource.url", postgres::getJdbcUrl)
+            registry.add("spring.datasource.username", postgres::getUsername)
+            registry.add("spring.datasource.password", postgres::getPassword)
+            // Wichtig: Flyway muss laufen, um Tabellen zu erstellen
+            registry.add("spring.flyway.enabled") { "true" }
+        }
+    }
+
+    @Test
+    fun `should save and load ping entity`() {
+        // Given
+        val pingId = Uuid.generateV7()
+        val ping = Ping(
+            id = pingId,
+            message = "Integration Test Ping",
+            timestamp = Instant.now()
+        )
+
+        // When
+        repositoryAdapter.save(ping)
+
+        // Then (via Adapter)
+        val loadedPing = repositoryAdapter.findById(pingId)
+        assertThat(loadedPing).isNotNull
+        assertThat(loadedPing?.message).isEqualTo("Integration Test Ping")
+        assertThat(loadedPing?.id).isEqualTo(pingId)
+
+        // Then (Direct DB Check via Spring Data)
+        // Fix: Use toJavaUuid() instead of UUID.fromString(pingId.toString())
+        val entity = springDataRepository.findById(pingId.toJavaUuid())
+        assertThat(entity).isPresent
+        assertThat(entity.get().message).isEqualTo("Integration Test Ping")
+    }
+}

backend/services/ping/ping-service/src/test/kotlin/at/mocode/ping/infrastructure/persistence/TestPersistenceConfig.kt

@@ -0,0 +1,16 @@
+package at.mocode.ping.infrastructure.persistence
+
+import org.springframework.boot.SpringBootConfiguration
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration
+import org.springframework.context.annotation.ComponentScan
+
+/**
+ * Minimale Konfiguration für DataJpaTests.
+ * Verhindert, dass die echte PingServiceApplication geladen wird,
+ * welche einen weiten ComponentScan auslöst und damit Controller/Services lädt,
+ * die wir im Repository-Test nicht brauchen (und die Fehler verursachen).
+ */
+@SpringBootConfiguration
+@EnableAutoConfiguration
+@ComponentScan(basePackages = ["at.mocode.ping.infrastructure.persistence"])
+class TestPersistenceConfig