any showcase for node:test `concurrency` options?

Details

as https://nodejs.org/dist/latest-v18.x/docs/api/test.html#testname-options-fn docs says, subtests could run concurrency.

when try as:

test('multi level test', { concurrency: 2 }, async (t) => {
  await t.test('subtest 1', async () => {
    console.log('1');
    await setTimeout(2000);
    console.log('11');
  });

  await t.test('subtest 2', async () => {
    console.log('2');
    await setTimeout(1000);
    console.log('22');
  });
});

itdon't work, since each subtests is awaited.

but if write test like below:

test('multi level test', { concurrency: 2 }, async (t) => {
  t.test('subtest 1', async () => {
    console.log('1');
    await setTimeout(2000);
    console.log('11');
  });

  t.test('subtest 2', async () => {
    console.log('2');
    await setTimeout(1000);
    console.log('22');
  });
});

got error:

not ok 1 - subtest 1
      ---
      duration_ms: 0.001728458
      failureType: 'cancelledByParent'
      error: "'test did not finish before its parent and was cancelled'"
      code: ERR_TEST_FAILURE
      ...

Node.js version

18.0.0

Example code

No response

Operating system

macOS

Scope

test

Module and version

Not applicable.