Refactor: Update error messages in user routes tests for clarity and consistency

src/routes/user.routes.test.ts

@@ -186,7 +186,7 @@ describe('User Routes (/api/users)', () => {
           .send({ category: 'Produce' });
         expect(response.status).toBe(400);
         // Check the 'errors' array for the specific validation message.
-        expect(response.body.errors[0].message).toContain("expected string, received undefined");
+        expect(response.body.errors[0].message).toBe("Field 'itemName' is required.");
       });
 
       it('should return 400 if category is missing', async () => {
@@ -195,7 +195,7 @@ describe('User Routes (/api/users)', () => {
           .send({ itemName: 'Apples' });
         expect(response.status).toBe(400);
         // Check the 'errors' array for the specific validation message.
-        expect(response.body.errors[0].message).toContain("expected string, received undefined");
+        expect(response.body.errors[0].message).toBe("Field 'category' is required.");
       });
     });
 
@@ -240,7 +240,7 @@ describe('User Routes (/api/users)', () => {
         const response = await supertest(app).post('/api/users/shopping-lists').send({});
         expect(response.status).toBe(400);
         // Check the 'errors' array for the specific validation message.
-        expect(response.body.errors[0].message).toContain("expected string, received undefined");
+        expect(response.body.errors[0].message).toBe("Field 'name' is required.");
       });
 
       it('should return 400 on foreign key constraint error', async () => {