fix testRegister_success

Change-Id: Ia125fff2481df66233819187a25de74f82ad34c3
diff --git a/src/main/java/com/g9/g9backend/service/InvitationService.java b/src/main/java/com/g9/g9backend/service/InvitationService.java
index 3708d53..bc17e9a 100644
--- a/src/main/java/com/g9/g9backend/service/InvitationService.java
+++ b/src/main/java/com/g9/g9backend/service/InvitationService.java
@@ -4,4 +4,7 @@
 import com.g9.g9backend.pojo.Invitation;
 
 public interface InvitationService extends IService<Invitation> {
+
+    // 定义生成邀请码的方法
+    String[] generateInvitationCode();
 }