diff --git a/backend/src/__tests__/app.test.js b/backend/src/__tests__/app.test.js
index 7e5df1e..42a5847 100644
--- a/backend/src/__tests__/app.test.js
+++ b/backend/src/__tests__/app.test.js
@@ -61,7 +61,7 @@ describe('Backend API Tests', () => {
     it('should have CORS headers', async () => {
       const response = await request(app)
         .get('/api/health')
-        .set('Origin', 'http://localhost:3000')
+        .set('Origin', 'http://localhost:8080')
         .expect(200);
 
       expect(response.headers).toHaveProperty('access-control-allow-origin');
diff --git a/backend/src/__tests__/auth-phase1.5.test.js b/backend/src/__tests__/auth-phase1.5.test.js
index d895adb..146e5d5 100644
--- a/backend/src/__tests__/auth-phase1.5.test.js
+++ b/backend/src/__tests__/auth-phase1.5.test.js
@@ -127,7 +127,8 @@ describe('Authentication API Tests - Phase 1.5', () => {
         })
         .expect(400);
 
-      expect(response.body.error).toContain('WSDC ID');
+      // Generic error message to prevent user enumeration
+      expect(response.body.error).toContain('already exists');
     });
 
     it('should continue registration even if email send fails', async () => {
@@ -484,7 +485,9 @@ describe('Authentication API Tests - Phase 1.5', () => {
         })
         .expect(400);
 
-      expect(response.body.error).toContain('8 characters');
+      expect(response.body.error).toBe('Validation Error');
+      expect(response.body.details).toBeDefined();
+      expect(response.body.details[0].msg).toContain('8 characters');
     });
 
     it('should reject invalid token', async () => {
diff --git a/backend/src/__tests__/socket.test.js b/backend/src/__tests__/socket.test.js
index b4f55a5..fe5aa90 100644
--- a/backend/src/__tests__/socket.test.js
+++ b/backend/src/__tests__/socket.test.js
@@ -129,10 +129,24 @@ describe('Socket.IO Server', () => {
           type: 'event',
         },
       });
+
+      // Create event participant (check-in) for test user
+      await prisma.eventParticipant.create({
+        data: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
     });
 
     afterAll(async () => {
       // Cleanup test data
+      await prisma.eventParticipant.deleteMany({
+        where: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
       await prisma.chatRoom.delete({
         where: { id: testChatRoom.id },
       });
@@ -147,7 +161,7 @@ describe('Socket.IO Server', () => {
       });
 
       clientSocket.on('connect', () => {
-        clientSocket.emit('join_event_room', { eventId: testEvent.id });
+        clientSocket.emit('join_event_room', { slug: testEvent.slug });
       });
 
       clientSocket.on('active_users', (users) => {
@@ -170,7 +184,7 @@ describe('Socket.IO Server', () => {
       });
 
       client1.on('connect', () => {
-        client1.emit('join_event_room', { eventId: testEvent.id });
+        client1.emit('join_event_room', { slug: testEvent.slug });
 
         // Create second user and join the same room
         const client2Token = generateToken({ userId: testUser.id });
@@ -187,7 +201,7 @@ describe('Socket.IO Server', () => {
         });
 
         client2.on('connect', () => {
-          client2.emit('join_event_room', { eventId: testEvent.id });
+          client2.emit('join_event_room', { slug: testEvent.slug });
         });
       });
     });
@@ -200,12 +214,11 @@ describe('Socket.IO Server', () => {
       const messageContent = 'Test message content';
 
       clientSocket.on('connect', () => {
-        clientSocket.emit('join_event_room', { eventId: testEvent.id });
+        clientSocket.emit('join_event_room', { slug: testEvent.slug });
 
         clientSocket.on('active_users', () => {
           // Wait for active_users, then send message
           clientSocket.emit('send_event_message', {
-            eventId: testEvent.id,
             content: messageContent,
           });
         });
@@ -242,12 +255,12 @@ describe('Socket.IO Server', () => {
       });
 
       clientSocket.on('connect', () => {
-        clientSocket.emit('join_event_room', { eventId: testEvent.id });
+        clientSocket.emit('join_event_room', { slug: testEvent.slug });
 
         clientSocket.on('active_users', (users) => {
           if (users.length > 0) {
             // User joined, now leave
-            clientSocket.emit('leave_event_room', { eventId: testEvent.id });
+            clientSocket.emit('leave_event_room');
             setTimeout(() => {
               done();
             }, 100);
@@ -429,9 +442,23 @@ describe('Socket.IO Server', () => {
           type: 'event',
         },
       });
+
+      // Create event participant (check-in) for test user
+      await prisma.eventParticipant.create({
+        data: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
     });
 
     afterAll(async () => {
+      await prisma.eventParticipant.deleteMany({
+        where: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
       await prisma.chatRoom.delete({
         where: { id: testChatRoom.id },
       });
@@ -455,12 +482,12 @@ describe('Socket.IO Server', () => {
 
       client1.on('connect', () => {
         client1Connected = true;
-        client1.emit('join_event_room', { eventId: testEvent.id });
+        client1.emit('join_event_room', { slug: testEvent.slug });
       });
 
       client2.on('connect', () => {
         client2Connected = true;
-        client2.emit('join_event_room', { eventId: testEvent.id });
+        client2.emit('join_event_room', { slug: testEvent.slug });
       });
 
       client2.on('user_left', (userData) => {
@@ -491,9 +518,23 @@ describe('Socket.IO Server', () => {
           endDate: new Date('2025-12-03'),
         },
       });
+
+      // Create event participant (check-in) for test user
+      await prisma.eventParticipant.create({
+        data: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
     });
 
     afterAll(async () => {
+      await prisma.eventParticipant.deleteMany({
+        where: {
+          userId: testUser.id,
+          eventId: testEvent.id,
+        },
+      });
       await prisma.event.delete({
         where: { id: testEvent.id },
       });
@@ -505,11 +546,10 @@ describe('Socket.IO Server', () => {
       });
 
       clientSocket.on('connect', () => {
-        clientSocket.emit('join_event_room', { eventId: testEvent.id });
+        clientSocket.emit('join_event_room', { slug: testEvent.slug });
 
         setTimeout(() => {
           clientSocket.emit('send_event_message', {
-            eventId: testEvent.id,
             content: 'Test message',
           });
         }, 100);