fix: Enhance error handling tests and add service status checks

### Summary of Changes
- Introduced new tests for `handleRequestError` to cover various error scenarios including connection timeouts and service errors.
- Added tests for `determineServiceStatus` to verify service availability states.
- Updated `formatServiceData` and `formatEventData` tests to ensure correct formatting and handling of invalid data.

### Expected Results
- Improved coverage and reliability of error handling utilities tests, ensuring accurate error responses and service status checks.
- Enhanced maintainability of test code by applying clean code principles and better organization.

frontend/src/setupTests.js

@@ -0,0 +1,5 @@
+// jest-dom adds custom jest matchers for asserting on DOM nodes.
+// allows you to do things like:
+// expect(element).toHaveTextContent(/react/i)
+// learn more: https://github.com/testing-library/jest-dom
+import '@testing-library/jest-dom';

frontend/src/utils/errorHandling.test.js

@@ -1,29 +1,51 @@
-import { formatError, formatServiceData, formatEventData } from './errorHandling'
+import { handleRequestError, determineServiceStatus, formatServiceData, formatEventData } from './errorHandling'
 
 describe('Error Handling Utils', () => {
-  describe('formatError', () => {
-    it('should format error objects correctly', () => {
-      const error = new Error('Test error message')
-      const formatted = formatError(error)
+  describe('handleRequestError', () => {
+    it('should handle connection timeout errors', () => {
+      const error = { code: 'ECONNABORTED' }
+      const result = handleRequestError(error)
       
-      expect(formatted).toHaveProperty('message', 'Test error message')
-      expect(formatted).toHaveProperty('type', 'Error')
+      expect(result).toHaveProperty('error')
+      expect(result.error).toContain('Request timeout')
     })
 
-    it('should handle string errors', () => {
-      const error = 'Simple string error'
-      const formatted = formatError(error)
+    it('should handle response errors', () => {
+      const error = { response: { status: 500 } }
+      const result = handleRequestError(error)
       
-      expect(formatted).toHaveProperty('message', 'Simple string error')
-      expect(formatted).toHaveProperty('type', 'string')
+      expect(result).toHaveProperty('error')
+      expect(result.error).toContain('Service error')
     })
 
-    it('should handle unknown error types', () => {
+    it('should handle request errors', () => {
+      const error = { request: {} }
+      const result = handleRequestError(error)
+      
+      expect(result).toHaveProperty('error')
+      expect(result.error).toContain('Service unavailable')
+    })
+
+    it('should handle unknown errors', () => {
       const error = { someProperty: 'value' }
-      const formatted = formatError(error)
+      const result = handleRequestError(error)
       
-      expect(formatted).toHaveProperty('message', 'Unknown error occurred')
-      expect(formatted).toHaveProperty('type', 'unknown')
+      expect(result).toHaveProperty('error')
+      expect(result.error).toContain('Unknown error')
+    })
+  })
+
+  describe('determineServiceStatus', () => {
+    it('should return offline when no services available', () => {
+      expect(determineServiceStatus(0, 3)).toBe('offline')
+    })
+
+    it('should return online when all services available', () => {
+      expect(determineServiceStatus(3, 3)).toBe('online')
+    })
+
+    it('should return partial when some services available', () => {
+      expect(determineServiceStatus(2, 3)).toBe('partial')
     })
   })
 
@@ -31,21 +53,31 @@ describe('Error Handling Utils', () => {
     it('should format service data correctly', () => {
       const rawData = {
         'api-gateway': {
+          name: 'API Gateway',
           status: 'healthy',
-          lastCheck: '2024-01-01T00:00:00.000Z'
+          responseTime: '1d 2h'
         }
       }
       
       const formatted = formatServiceData(rawData)
       
-      expect(formatted).toHaveProperty('api-gateway')
-      expect(formatted['api-gateway']).toHaveProperty('status', 'healthy')
-      expect(formatted['api-gateway']).toHaveProperty('lastCheck')
+      expect(Array.isArray(formatted)).toBe(true)
+      expect(formatted).toHaveLength(1)
+      expect(formatted[0]).toHaveProperty('name', 'API Gateway')
+      expect(formatted[0]).toHaveProperty('status', 'online')
+      expect(formatted[0]).toHaveProperty('uptime', '1d 2h')
     })
 
     it('should handle empty data', () => {
       const formatted = formatServiceData({})
-      expect(formatted).toEqual({})
+      expect(Array.isArray(formatted)).toBe(true)
+      expect(formatted).toHaveLength(0)
+    })
+
+    it('should handle invalid data', () => {
+      const formatted = formatServiceData(null)
+      expect(Array.isArray(formatted)).toBe(true)
+      expect(formatted).toHaveLength(0)
     })
   })
 
@@ -53,7 +85,6 @@ describe('Error Handling Utils', () => {
     it('should format event data correctly', () => {
       const rawEvents = [
         {
-          id: '1',
           timestamp: '2024-01-01T00:00:00.000Z',
           service: 'api-gateway',
           event_type: 'health_check'
@@ -63,7 +94,9 @@ describe('Error Handling Utils', () => {
       const formatted = formatEventData(rawEvents)
       
       expect(Array.isArray(formatted)).toBe(true)
-      expect(formatted[0]).toHaveProperty('id', '1')
+      expect(formatted).toHaveLength(1)
+      expect(formatted[0]).toHaveProperty('time')
+      expect(formatted[0]).toHaveProperty('event', 'health_check from api-gateway')
       expect(formatted[0]).toHaveProperty('service', 'api-gateway')
     })
 
@@ -72,5 +105,11 @@ describe('Error Handling Utils', () => {
       expect(Array.isArray(formatted)).toBe(true)
       expect(formatted).toHaveLength(0)
     })
+
+    it('should handle invalid data', () => {
+      const formatted = formatEventData(null)
+      expect(Array.isArray(formatted)).toBe(true)
+      expect(formatted).toHaveLength(0)
+    })
   })
 })