feat: JPA @table 설정 추가 및 멱등성 통합 테스트 구현

- `OutboxEvent`, `ProductMetrics`, `EventHandled` 엔티티에 @table 애너테이션 추가.
- `IdempotencyIntegrationTest` 구현으로 중복 이벤트 처리 검증.

Author: yeonjiyeon

apps/commerce-api/src/main/java/com/loopers/domain/event/OutboxEvent.java

@@ -5,12 +5,14 @@
 import jakarta.persistence.GeneratedValue;
 import jakarta.persistence.GenerationType;
 import jakarta.persistence.Id;
+import jakarta.persistence.Table;
 import java.time.LocalDateTime;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
 @Entity
 @Getter
+@Table(name = "outbox_event")
 @NoArgsConstructor
 public class OutboxEvent {
 

apps/commerce-streamer/src/main/java/com/loopers/domain/event/EventHandled.java

@@ -2,13 +2,15 @@
 
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
+import jakarta.persistence.Table;
 import java.time.LocalDateTime;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
 @Entity
 @Getter
+@Table(name = "event_handled")
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class EventHandled {
 

apps/commerce-streamer/src/main/java/com/loopers/domain/metrics/ProductMetrics.java

@@ -2,13 +2,15 @@
 
 import jakarta.persistence.Entity;
 import jakarta.persistence.Id;
+import jakarta.persistence.Table;
 import java.time.LocalDateTime;
 import lombok.AccessLevel;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 
 @Entity
 @Getter
+@Table(name = "product_metrics")
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class ProductMetrics {
 

apps/commerce-streamer/src/test/java/com/loopers/domain/metrics/IdempotencyIntegrationTest.java

@@ -0,0 +1,55 @@
+package com.loopers.domain.metrics;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.loopers.event.SalesCountEvent;
+import com.loopers.infrastructure.ProductMetricsRepository;
+import com.loopers.utils.DatabaseCleanUp;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class IdempotencyIntegrationTest {
+
+  @Autowired
+  private ProductMetricsService metricsService;
+
+  @Autowired
+  private ProductMetricsRepository metricsRepository;
+
+  @Autowired
+  private DatabaseCleanUp databaseCleanUp;
+
+  @AfterEach
+  void tearDown() {
+    databaseCleanUp.truncateAllTables();
+  }
+
+
+  @Test
+  @DisplayName("중복 이벤트 수신 시에도 메트릭 수치는 단 한 번만 반영되어야 한다")
+  void shouldHandleDuplicateEventIdempotently() {
+    // Given: 동일한 ID를 가진 이벤트 준비
+    Long productId = 99L;
+    int salesQuantity = 2;
+
+    SalesCountEvent firstEvent = SalesCountEvent.of(productId, salesQuantity);
+
+    // When: 첫 번째 전송
+    metricsService.processSalesCountEvent(firstEvent);
+
+    // Then: 수치 반영 확인
+    int firstResult = metricsRepository.findById(productId).get().getSalesCount();
+    assertThat(firstResult).isEqualTo(2);
+
+    // When: 동일 ID로 두 번째 전송 (Kafka 재전송 시나리오)
+    metricsService.processSalesCountEvent(firstEvent);
+
+    // Then: 수치가 4가 아니라 여전히 2여야 함 (멱등성 성공)
+    int secondResult = metricsRepository.findById(productId).get().getSalesCount();
+    assertThat(secondResult).isEqualTo(2);
+  }
+}