Function startDualLoopbackUpstream

packages/cli/src/commands/ui.test.ts:162–196

(
  handler: Parameters<typeof createHttpServer>[1],
)

type UpstreamSurrogate = { port: number; close: () => Promise<void> };

async function startDualLoopbackUpstream(
  handler: Parameters<typeof createHttpServer>[1],
): Promise<UpstreamSurrogate> {
  const v6 = createHttpServer(handler);
  await new Promise<void>((done, fail) => {
    v6.once('error', fail);
    v6.listen(0, '::1', () => {
      v6.off('error', fail);
      done();
    });
  });
  const port = (v6.address() as { port: number }).port;
  const v4 = createHttpServer(handler);
  try {
    await new Promise<void>((done, fail) => {
      v4.once('error', fail);
      v4.listen(port, '127.0.0.1', () => {
        v4.off('error', fail);
        done();
      });
    });
  } catch (err) {
    await new Promise<void>((r) => v6.close(() => r()));
    throw err;
  }
  return {
    port,
    close: async () => {
      await Promise.all([
        new Promise<void>((r) => v6.close(() => r())),
        new Promise<void>((r) => v4.close(() => r())),
      ]);
    },
  };
}

describe('resolveRequestedPort', () => {
  test('default is DEFAULT_UI_PORT with kernel-allocated fallback', () => {