feat: enhance testing framework with new test cases and configurations

backend/src/utils/asyncHandler.test.ts

@@ -0,0 +1,37 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { asyncHandler } from './asyncHandler'
+import type { Request, Response, NextFunction } from 'express'
+
+const mockReq = {} as Request
+const mockRes = {} as Response
+let mockNext: NextFunction
+
+beforeEach(() => {
+  mockNext = vi.fn() as unknown as NextFunction
+})
+
+describe('asyncHandler', () => {
+  it('calls next with error when async handler throws', async () => {
+    const error = new Error('boom')
+    const handler = asyncHandler(async () => {
+      throw error
+    })
+    await handler(mockReq, mockRes, mockNext)
+    expect(mockNext).toHaveBeenCalledWith(error)
+  })
+
+  it('does not call next when handler resolves', async () => {
+    const handler = asyncHandler(async () => {
+      // success
+    })
+    await handler(mockReq, mockRes, mockNext)
+    expect(mockNext).not.toHaveBeenCalled()
+  })
+
+  it('calls next with error when handler rejects', async () => {
+    const error = new Error('rejected')
+    const handler = asyncHandler(() => Promise.reject(error))
+    await handler(mockReq, mockRes, mockNext)
+    expect(mockNext).toHaveBeenCalledWith(error)
+  })
+})