Test fixture และ setup/teardown คืออะไร?

SETUP → runs BEFORE tests to prepare the context (create objects, data, connections)
TEARDOWN → runs AFTER tests to CLEAN UP (close connections, delete data, reset state)
→ frameworks provide hooks:
  beforeEach / afterEach → before/after EACH test (fresh state per test — common)
  beforeAll / afterAll → once before/after ALL tests in a group (shared expensive setup)

(,  {
   service, db;
  ( {                 
    db = ();
    service =  (db);
  });
  ( db.());        

  (,  {  });
});