test: enhance helmet middleware tests for Koa integration

- Updated test descriptions for clarity.
- Added tests to verify middleware creation and option handling.
- Included error handling test for express helmet middleware.

Author: csikb

src/middleware/helmet.test.ts

@@ -1,15 +1,87 @@
 import helmet from 'helmet'
+import type { Context } from 'koa'
 import { describe, expect, it, vi } from 'vitest'
 
 vi.mock('helmet')
 
 describe('helmet', () => {
-  it('should export helmet', async () => {
+  it('should export a function that wraps helmet for Koa', async () => {
     expect.assertions(2)
 
-    const { default: actual } = await import('./helmet.js')
+    const { default: helmetMiddleware } = await import('./helmet.js')
 
-    expect(helmet).toHaveBeenCalledOnce()
-    expect(actual).toStrictEqual(helmet)
+    expect(helmetMiddleware).toBeTypeOf('function')
+
+    // Call the function to create middleware
+    const middleware = helmetMiddleware()
+
+    expect(middleware).toBeTypeOf('function')
+  })
+
+  it('should call helmet with options when provided', async () => {
+    expect.assertions(1)
+
+    const mockHelmet = vi.mocked(helmet)
+    mockHelmet.mockReturnValue(vi.fn())
+
+    const { default: helmetMiddleware } = await import('./helmet.js')
+
+    const options = { contentSecurityPolicy: false }
+    helmetMiddleware(options)
+
+    expect(mockHelmet).toHaveBeenCalledWith(options)
+  })
+
+  it('should call the express helmet middleware and continue to next', async () => {
+    expect.assertions(2)
+
+    const mockExpressHelmet = vi.fn((_req, _res, next) => {
+      next()
+    })
+    const mockHelmet = vi.mocked(helmet)
+    mockHelmet.mockReturnValue(mockExpressHelmet)
+
+    const { default: helmetMiddleware } = await import('./helmet.js')
+
+    const middleware = helmetMiddleware()
+
+    const ctx = {
+      req: {},
+      res: {},
+    } as Context
+    const next = vi.fn().mockResolvedValue(undefined)
+
+    await middleware(ctx, next)
+
+    expect(mockExpressHelmet).toHaveBeenCalledWith(
+      ctx.req,
+      ctx.res,
+      expect.any(Function),
+    )
+    expect(next).toHaveBeenCalledOnce()
+  })
+
+  it('should reject promise when express helmet middleware returns error', async () => {
+    expect.assertions(2)
+
+    const error = new Error('Helmet error')
+    const mockExpressHelmet = vi.fn((_req, _res, callback) => {
+      callback(error)
+    })
+    const mockHelmet = vi.mocked(helmet)
+    mockHelmet.mockReturnValue(mockExpressHelmet)
+
+    const { default: helmetMiddleware } = await import('./helmet.js')
+
+    const middleware = helmetMiddleware()
+
+    const ctx = {
+      req: {},
+      res: {},
+    } as Context
+    const next = vi.fn()
+
+    await expect(middleware(ctx, next)).rejects.toThrow('Helmet error')
+    expect(next).not.toHaveBeenCalled()
   })
 })