Testing Nuxt Server Side Routes

Question

I am learning and coding a Nuxt application example and try to test all files. Once is left:

 % Coverage report from v8
----------------------------|---------|----------|---------|---------|-------------------
File                        | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------------------------|---------|----------|---------|---------|-------------------
...
nuxt-boil/server/api        |       0 |        0 |       0 |       0 |                    
  env.ts                    |       0 |        0 |       0 |       0 | 1-4

server/api/env.ts

export default defineEventHandler(async (event) => {
    const { NUXT_API_SECRET } = process.env
    return NUXT_API_SECRET
})

tests/server/api/env.test.ts

import { setup } from '@nuxt/test-utils'
import { $fetch } from '@nuxt/test-utils/e2e'

describe('route: /api/env', async () => {
    await setup({
        server: true
    })

    test('return env NUXT_API_SECRET', async () => {
        const { data } = await useAsyncData(() => $fetch('/api/env'))
        expect(data.value).toEqual(import.meta.env.NUXT_API_SECRET)
    })
})

Test result is

...
✓ tests/server/api/env.test.ts (1) 12868ms

I tried to find different solutions for testing routes.

Could you provide tests for 100% coverage (v8/istanbul)? I think I have (as usual) a basic understanding problem :-)