ci codecov

Pact is a contract testing tool to help you replace expensive and brittle end-to-end integration tests with fast, reliable and easy to debug unit tests. This framework provides a Dart DSL for generating Pact contracts. It implements Pact Specification v3 using the Pact FFI Library.


This readme offers an basic introduction to the library. View more documentation on Pact at

Need Help


# install pact_dart as a dev dependency
dart pub add --dev pact_dart

# download and install the required libraries
dart run pact_dart:install

# 🚀 now write some tests!
Flutter Instructions

Flutter Installation

# install pact_dart as a dev dependency
flutter pub add --dev pact_dart

# download and install the required libraries
flutter pub run pact_dart:install

# 🚀 now write some tests!
Manual Installation Instructions

Modify Library Location

By default, the Pact FFI Library is installed to /usr/local/lib on macOS and Linux. However, you can use the PACT_DART_LIB_DOWNLOAD_PATH environment variable to modify the installation path.

PACT_DART_LIB_DOWNLOAD_PATH=/app/my-other-location dart run pact_dart:install

Manual Installation

Download the latest Pact FFI Library libraries for your OS, and install onto a standard library search path (for example, we suggest: /usr/local/lib on OSX/Linux):

Ensure you have the correct extension for your OS:

  • For Mac OSX: .dylib
  • For Linux: .so
  • For Windows: .dll
gunzip libpact_ffi-osx-x86_64.dylib.gz
mv libpact_ffi-osx-x86_64.dylib /usr/local/lib/libpact_ffi.dylib


Writing a Consumer test

Pact is a consumer-driven contract testing tool, which is a fancy way of saying that the API Consumer writes a test to set out its assumptions and needs of its API Provider(s). By unit testing our API client with Pact, it will produce a contract that we can share to our Provider to confirm these assumptions and prevent breaking changes.

In this example, we are testing the users repository that communicates with the /users resource of a HTTP service. The repository has a single method fetchAll() that will return a list of users.

import 'package:pact_dart/pact_dart.dart';

final pact = PactMockService('FlutterConsumer','APIService');

    .given('a user exists', params: {'first_name': 'Betsy', 'last_name': 'Tester'})
    .uponReceiving('a request for all users')
    .withRequest('GET', '/users')
    .willRespondWith(200, body: {
        // Matchers are used here as we care about the types and structure of the response and not the exact values.
        'page': PactMatchers.SomethingLike(1),
        'per_page': PactMatchers.SomethingLike(20),
        'total': PactMatchers.IntegerLike(20),
        'total_pages': PactMatchers.SomethingLike(3),
        'data': PactMatchers.EachLike([
                'id': PactMatchers.uuid('f3a9cf4a-92d7-4aae-a945-63a6440b528b'),
                'first_name': PactMatchers.SomethingLike('Betsy'),
                'last_name': PactMatchers.SomethingLike('Tester'),
                'salary': PactMatchers.DecimalLike(125000.00)
    }); false);

final loginRepository = UsersRepository();
final users = await loginRepository.fetchAll();

expect(users.count, equals(20));
expect(users[0].first_name, equals('Betsy'));
expect(users[0].last_name, equals('Tester'));



Feature Compatibility
HTTP Pacts
Asychronous message pacts
Regular expression matching
Type based matching ("like")
Flexible array length ("each like")
Verify a pact that uses the Pact specification v3 format
Pact specification v3 matchers🔨
Pact specification v3 generators
Multiple provider states (pact creation)
Multiple provider states (pact verification)
Publish pacts to Pact Broker
Tag consumer version in Pact Broker when publishing pact
Dynamically fetch pacts for provider from Pact Broker for verification
Dynamically fetch pacts for provider with specified tags
Automatically tag consumer/provider with name of git branch
Use 'pacts for verification' Pact Broker API
Pending pacts
WIP pacts
JSON test results output
XML test results output
Markdown test results output
Run a single interaction when verifying a pact
Injecting values from provider state callbacks
Date/Time expressions with generators
  • ✅ -- Implemented
  • 🔨 -- Partially implemented
  • ❌ -- Not implemented