betamax Pub test

Record your test suite's HTTP interactions and replay them during future test runs for fast, deterministic, accurate tests.


  • Recording and playback of arbitrary HTTP interactions sequences
  • Naming of fixtures based on the names of your tests, and their groups
  • Automatic test failure (in playback mode) when expected requests do not arrive
  • Support for the entire set of http's request types — basic, streamed, and multipart
  • HTTP proxy support while in record mode, via findProxyFromEnvironment
  • Easy set up!

Inspired by Ruby's VCR gem.

Getting started

Latest Release

  betamax: ^1.0.0


import 'dart:io';

import 'package:betamax/betamax.dart';
import 'package:http/http.dart' as http;
import 'package:test/test.dart';

void main() async {
  setUpAll(() {
    // We use an environment variable to determine whether we should be
    // recording or playing back HTTP interactions.
    final recordFixtures =
        Platform.environment['RECORD_HTTP_FIXTURES'] == 'true';

      // The name of the test suite (I generally name this according to file)
      suiteName: 'echo',
      // Whether to record HTTP traffic passing through Betamax clients, or
      // to playback existing fixtures
      mode: recordFixtures ? Mode.recording : Mode.playback,
      // Path relative to `/test` where your fixtures should be stored
      relativeCassettePath: 'http_fixtures',

  late http.Client httpClient;
  setUp(() {
    // Sets up a new client according to the options provided to
    // `configureSuite`.
    httpClient = Betamax.clientForTest();

  // Writes/reads a cassette (http fixture) to
  // `/test/http_fixtures/echo/response_is_ok.json`
  test('response is OK', () async {
    final response =
        await httpClient.get(Uri.parse(''));
    expect(response.statusCode, 200);