Runs before the request is sent. Set or override variables, build dynamic headers, generate timestamps etc.
env.get('key') — read variable  |  env.set('key', val) — write variable  |  request.url request.method request.headers — read current request

Runs after the response arrives. Write tests, extract tokens, chain requests.
response.status response.body response.json() — read response  |  env.set('key', val) — save values to env  |  test('name', () => { ... }) — write a test assertion