diff --git a/src/routes/admin.content.routes.test.ts b/src/routes/admin.content.routes.test.ts
index ea5d764c..7b02224c 100644
--- a/src/routes/admin.content.routes.test.ts
+++ b/src/routes/admin.content.routes.test.ts
@@ -116,6 +116,12 @@ describe('Admin Content Management Routes (/api/admin)', () => {
   // Create a single app instance with an admin user for all tests in this suite.
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/admin.jobs.routes.test.ts b/src/routes/admin.jobs.routes.test.ts
index eb6b218c..bf7f56fe 100644
--- a/src/routes/admin.jobs.routes.test.ts
+++ b/src/routes/admin.jobs.routes.test.ts
@@ -92,6 +92,12 @@ describe('Admin Job Trigger Routes (/api/admin/trigger)', () => {
   // Create a single app instance with an admin user for all tests in this suite.
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/admin.monitoring.routes.test.ts b/src/routes/admin.monitoring.routes.test.ts
index 12d3735b..bb905146 100644
--- a/src/routes/admin.monitoring.routes.test.ts
+++ b/src/routes/admin.monitoring.routes.test.ts
@@ -102,6 +102,12 @@ describe('Admin Monitoring Routes (/api/admin)', () => {
   // Create a single app instance with an admin user for all tests in this suite.
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/admin.stats.routes.test.ts b/src/routes/admin.stats.routes.test.ts
index aa955466..43507dbf 100644
--- a/src/routes/admin.stats.routes.test.ts
+++ b/src/routes/admin.stats.routes.test.ts
@@ -74,6 +74,12 @@ describe('Admin Stats Routes (/api/admin/stats)', () => {
   // Create a single app instance with an admin user for all tests in this suite.
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/admin.system.routes.test.ts b/src/routes/admin.system.routes.test.ts
index 22483678..56c06917 100644
--- a/src/routes/admin.system.routes.test.ts
+++ b/src/routes/admin.system.routes.test.ts
@@ -64,6 +64,12 @@ describe('Admin System Routes (/api/admin/system)', () => {
   const adminUser = createMockUserProfile({ role: 'admin' });
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/admin.users.routes.test.ts b/src/routes/admin.users.routes.test.ts
index b3406b72..1b0754cf 100644
--- a/src/routes/admin.users.routes.test.ts
+++ b/src/routes/admin.users.routes.test.ts
@@ -81,6 +81,12 @@ describe('Admin User Management Routes (/api/admin/users)', () => {
   // Create a single app instance with an admin user for all tests in this suite.
   const app = createTestApp({ router: adminRouter, basePath: '/api/admin', authenticatedUser: adminUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/ai.routes.test.ts b/src/routes/ai.routes.test.ts
index 53f8fc8c..6f4fb782 100644
--- a/src/routes/ai.routes.test.ts
+++ b/src/routes/ai.routes.test.ts
@@ -76,6 +76,12 @@ describe('AI Routes (/api/ai)', () => {
   });
   const app = createTestApp({ router: aiRouter, basePath: '/api/ai' });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   describe('POST /upload-and-process', () => {
     const imagePath = path.resolve(__dirname, '../tests/assets/test-flyer-image.jpg');
 
diff --git a/src/routes/budget.routes.test.ts b/src/routes/budget.routes.test.ts
index d9997862..80bf4f93 100644
--- a/src/routes/budget.routes.test.ts
+++ b/src/routes/budget.routes.test.ts
@@ -63,6 +63,12 @@ describe('Budget Routes (/api/budgets)', () => {
   
   const app = createTestApp({ router: budgetRouter, basePath: '/api/budgets', authenticatedUser: mockUser });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
     describe('GET /', () => {
       it('should return a list of budgets for the user', async () => {
         const mockBudgets = [createMockBudget({ budget_id: 1, user_id: 'user-123' })];
diff --git a/src/routes/deals.routes.test.ts b/src/routes/deals.routes.test.ts
index b8bf4f8c..8708a36f 100644
--- a/src/routes/deals.routes.test.ts
+++ b/src/routes/deals.routes.test.ts
@@ -46,6 +46,13 @@ describe('Deals Routes (/api/users/deals)', () => {
   const basePath = '/api/users/deals';
   const authenticatedApp = createTestApp({ router: dealsRouter, basePath, authenticatedUser: mockUser });
   const unauthenticatedApp = createTestApp({ router: dealsRouter, basePath });
+  const errorHandler = (err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  };
+
+  // Apply the handler to both app instances
+  authenticatedApp.use(errorHandler);
+  unauthenticatedApp.use(errorHandler);
 
   beforeEach(() => {
     vi.clearAllMocks();
@@ -67,5 +74,13 @@ describe('Deals Routes (/api/users/deals)', () => {
       expect(response.body).toEqual(mockDeals);
       expect(dealsRepo.findBestPricesForWatchedItems).toHaveBeenCalledWith(mockUser.user_id, expectLogger);
     });
+
+    it('should return 500 if the database call fails', async () => {
+      vi.mocked(dealsRepo.findBestPricesForWatchedItems).mockRejectedValue(new Error('DB Error'));
+
+      const response = await supertest(authenticatedApp).get('/api/users/deals/best-watched-prices');
+      expect(response.status).toBe(500);
+      expect(response.body.message).toBe('DB Error');
+    });
   });
 });
\ No newline at end of file
diff --git a/src/routes/flyer.routes.test.ts b/src/routes/flyer.routes.test.ts
index 567015ed..3f49b75b 100644
--- a/src/routes/flyer.routes.test.ts
+++ b/src/routes/flyer.routes.test.ts
@@ -41,6 +41,12 @@ describe('Flyer Routes (/api/flyers)', () => {
   
   const app = createTestApp({ router: flyerRouter, basePath: '/api/flyers' });
 
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   describe('GET /', () => {
     it('should return a list of flyers on success', async () => {
       const mockFlyers = [createMockFlyer({ flyer_id: 1 }), createMockFlyer({ flyer_id: 2 })];
diff --git a/src/routes/gamification.routes.test.ts b/src/routes/gamification.routes.test.ts
index 5cb9db03..eebc9999 100644
--- a/src/routes/gamification.routes.test.ts
+++ b/src/routes/gamification.routes.test.ts
@@ -66,6 +66,12 @@ describe('Gamification Routes (/api/achievements)', () => {
   const unauthenticatedApp = createTestApp({ router: gamificationRouter, basePath });
   const authenticatedApp = createTestApp({ router: gamificationRouter, basePath, authenticatedUser: mockUserProfile });
   const adminApp = createTestApp({ router: gamificationRouter, basePath, authenticatedUser: mockAdminProfile });
+  const errorHandler = (err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  };
+  unauthenticatedApp.use(errorHandler);
+  authenticatedApp.use(errorHandler);
+  adminApp.use(errorHandler);
 
   describe('GET /', () => {
     it('should return a list of all achievements (public endpoint)', async () => {
diff --git a/src/routes/personalization.routes.test.ts b/src/routes/personalization.routes.test.ts
index 268886f0..efacb955 100644
--- a/src/routes/personalization.routes.test.ts
+++ b/src/routes/personalization.routes.test.ts
@@ -25,6 +25,13 @@ import * as db from '../services/db/index.db';
 
 describe('Personalization Routes (/api/personalization)', () => {
   const app = createTestApp({ router: personalizationRouter, basePath: '/api/personalization' });
+
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/recipe.routes.test.ts b/src/routes/recipe.routes.test.ts
index c52524b7..0ef38261 100644
--- a/src/routes/recipe.routes.test.ts
+++ b/src/routes/recipe.routes.test.ts
@@ -33,6 +33,13 @@ const expectLogger = expect.objectContaining({
 
 describe('Recipe Routes (/api/recipes)', () => {
   const app = createTestApp({ router: recipeRouter, basePath: '/api/recipes' });
+
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/stats.routes.test.ts b/src/routes/stats.routes.test.ts
index b278e656..9d9ad9c6 100644
--- a/src/routes/stats.routes.test.ts
+++ b/src/routes/stats.routes.test.ts
@@ -27,6 +27,13 @@ const expectLogger = expect.objectContaining({
 
 describe('Stats Routes (/api/stats)', () => {
   const app = createTestApp({ router: statsRouter, basePath: '/api/stats' });
+
+  // Add a basic error handler to capture errors passed to next(err) and return JSON.
+  // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+  app.use((err: any, req: any, res: any, next: any) => {
+    res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+  });
+
   beforeEach(() => {
     vi.clearAllMocks();
   });
diff --git a/src/routes/user.routes.test.ts b/src/routes/user.routes.test.ts
index 28834ecb..eaed8731 100644
--- a/src/routes/user.routes.test.ts
+++ b/src/routes/user.routes.test.ts
@@ -130,6 +130,12 @@ describe('User Routes (/api/users)', () => {
     const mockUserProfile = createMockUserProfile({ user_id: 'user-123' });
     const app = createTestApp({ router: userRouter, basePath, authenticatedUser: mockUserProfile });
 
+    // Add a basic error handler to capture errors passed to next(err) and return JSON.
+    // This prevents unhandled error crashes in tests and ensures we get the 500 response we expect.
+    app.use((err: any, req: any, res: any, next: any) => {
+      res.status(err.status || 500).json({ message: err.message, errors: err.errors });
+    });
+
     beforeEach(() => {
       // All tests in this block will use the authenticated app
     });