pact-go

README

Pact Go

Fast, easy and reliable testing for your APIs and microservices.

Pact is the de-facto API contract testing tool. Replace expensive and brittle end-to-end integration tests with fast, reliable and easy to debug unit tests. ⚡ Lightning fast 🎈 Effortless full-stack integration testing - from the front-end to the back-end 🔌 Supports HTTP/REST and event-driven systems 🛠️ Configurable mock server 😌 Powerful matching rules prevents brittle tests 🤝 Integrates with Pact Broker / Pactflow for powerful CI/CD workflows 🔡 Supports 12+ languages Why use Pact? Contract testing with Pact lets you: ⚡ Test locally 🚀 Deploy faster ⬇️ Reduce the lead time for change 💰 Reduce the cost of API integration testing 💥 Prevent breaking changes 🔎 Understand your system usage 📃 Document your APIs for free 🗄 Remove the need for complex data fixtures 🤷‍♂️ Reduce the reliance on complex test environments Watch our series on the problems with end-to-end integrated tests, and how contract testing can help.

Documentation

This readme offers an basic introduction to the library. The full documentation for Pact Go and the rest of the framework is available at https://docs.pact.io/.

• Installation
• Consumer Testing
• Provider Testing
• Event Driven Systems
• Migration guide
• Troubleshooting

Tutorial (60 minutes)

Learn everything in Pact Go in 60 minutes: https://github.com/pact-foundation/pact-workshop-go

Need Help

• Join our community slack workspace.
• Stack Overflow: https://stackoverflow.com/questions/tagged/pact
• Say 👋 on Twitter: @pact_up

Installation

# install pact-go as a dev dependency
go get github.com/pact-foundation/pact-go/v2@2.x.x

# NOTE: If using Go 1.19 or later, you need to run go install instead 
# go install github.com/pact-foundation/pact-go/v2@2.x.x

# download and install the required libraries. The pact-go will be installed into $GOPATH/bin, which is $HOME/go/bin by default. 
pact-go -l DEBUG install 

# 🚀 now write some tests!

If the pact-go command above is not found, make sure that $GOPATH/bin is in your path. I.e.,

export GOPATH=$HOME/go
export PATH=$PATH:$GOPATH/bin

You can also keep the library versions up to date by running the version.CheckVersion() function.

Manual Installation Instructions

Manual

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

Ensure you have the correct extension for your OS:

• For Mac OSX: .dylib (For M1 users, you need the aarch64-apple-darwin version)
• For Linux: .so
• For Windows: .dll

wget https://github.com/pact-foundation/pact-reference/releases/download/libpact_ffi-v0.1.2/libpact_ffi-osx-x86_64.dylib.gz
gunzip libpact_ffi-osx-x86_64.dylib.gz
mv libpact_ffi-osx-x86_64.dylib /usr/local/lib/libpact_ffi.dylib

Test the installation:

pact-go help

Usage

Consumer package

The consumer interface is in the package: github.com/pact-foundation/pact-go/v2/consumer.

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 going to be testing our User API client, responsible for communicating with the UserAPI over HTTP. It currently has a single method GetUser(id) that will return a *User.

Pact tests have a few key properties. We'll demonstrate a common example using the 3A Arrange/Act/Assert pattern.

func TestUserAPIClient(t *testing.T) {
	// Specify the two applications in the integration we are testing
	// NOTE: this can usually be extracted out of the individual test for re-use)
	mockProvider, err := NewV2Pact(MockHTTPProviderConfig{
		Consumer: "UserAPIConsumer",
		Provider: "UserAPI",
	})
	assert.NoError(t, err)

	// Arrange: Setup our expected interactions
	mockProvider.
		AddInteraction().
		Given("A user with ID 10 exists").
		UponReceiving("A request for User 10").
		WithRequest("GET", S("/user/10")).
		WillRespondWith(200).
		WithBodyMatch(&User{})

	// Act: test our API client behaves correctly
	err = mockProvider.ExecuteTest(func(config MockServerConfig) error {
		// Initialise the API client and point it at the Pact mock server
		// Pact spins up a dedicated mock server for each test
		client := newClient(config.Host, config.Port)

		// Execute the API client
		user, err := client.GetUser("10")

		// Assert: check the result
		assert.NoError(t, err)
		assert.Equal(t, 10, user.ID)

		return err
	})
	assert.NoError(t, err)
}

You can see (and run) the full version of this in ./examples/basic_test.go.

For a full example, see the Pactflow terraform provider pact tests.

Provider package

The provider interface is in the package: github.com/pact-foundation/pact-go/v2/provider

Verifying a Provider

A provider test takes one or more pact files (contracts) as input, and Pact verifies that your provider adheres to the contract. In the simplest case, you can verify a provider as per below.

func TestV3HTTPProvider(t *testing.T) {
	// 1. Start your Provider API in the background
	go startServer()

	verifier := HTTPVerifier{}

	// Verify the Provider with local Pact Files
	// The console will display if the verification was successful or not, the
	// assertions being made and any discrepancies with the contract
	err := verifier.VerifyProvider(t, VerifyRequest{
		ProviderBaseURL: "http://localhost:1234",
		PactFiles: []string{
			filepath.ToSlash("/path/to/SomeConsumer-SomeProvider.json"),
		},
	})

	// Ensure the verification succeeded
	assert.NoError(t, err)
}

Compatibility

Specification Compatibility

Version	Stable	Spec Compatibility	Install
2.0.x	Yes	2, 3, 4	See installation
1.0.x	Yes	2, 3*	1.x.x 1xx
0.x.x	Yes	Up to v2	0.x.x stable

* v3 support is limited to the subset of functionality required to enable language inter-operable Message support.

Roadmap

The roadmap for Pact and Pact Go is outlined on our main website. Detail on the native Go implementation can be found here.

Contributing

See CONTRIBUTING.

Documentation

Overview

Pact Go enables consumer driven contract testing, providing a mock service and DSL for the consumer project, and interaction playback and verification for the service provider project.

Consumer Tests

Consumer side Pact testing is an isolated test that ensures a given component is able to collaborate with another (remote) component. Pact will automatically start a Mock server in the background that will act as the collaborators' test double.

This implies that any interactions expected on the Mock server will be validated, meaning a test will fail if all interactions were not completed, or if unexpected interactions were found:

A typical consumer-side test would look something like this:

	func TestLogin(t *testing.T) {

		// Create Pact client
		pact := Pact{
			Consumer: "My Consumer",
			Provider: "My Provider",
		}
		// Shuts down Mock Service when done
		defer pact.Teardown()

		// Pass in your test case as a function to Verify()
		var test = func() error {
			_, err := http.Get("http://localhost:8000/")
			return err
		}

    // Set up our expected interactions.
    pact.
      AddInteraction().
      Given("User foo exists").
      UponReceiving("A request to get foo").
      WithRequest(dsl.Request{
        Method:  "GET",
        Path:    dsl.String("/foobar"),
        Headers: dsl.MapMatcher{"Content-Type": "application/json"},
      }).
      WillRespondWith(dsl.Response{
        Status:  200,
        Headers: dsl.MapMatcher{"Content-Type": "application/json"},
        Body:    dsl.Match(&Foo{})
      })

    // Verify
    if err := pact.Verify(test); err != nil {
      log.Fatalf("Error on Verify: %v", err)
    }
  }

If this test completed successfully, a Pact file should have been written to ./pacts/my_consumer-my_provider.json containing all of the interactions expected to occur between the Consumer and Provider.

Matching

In addition to verbatim value matching, you have 3 useful matching functions in the `dsl` package that can increase expressiveness and reduce brittle test cases.

Term(example, matcher)	tells Pact that the value should match using a given regular expression, using `example` in mock responses. `example` must be a string.
Like(content)		tells Pact that the value itself is not important, as long as the element _type_ (valid JSON number, string, object etc.) itself matches.
EachLike(content, min)	tells Pact that the value should be an array type, consisting of elements like those passed in. `min` must be >= 1. `content` may be a valid JSON value: e.g. strings, numbers and objects.

Here is a complex example that shows how all 3 terms can be used together:

  	body :=
		Like(map[string]interface{}{
			"response": map[string]interface{}{
				"name": Like("Billy"),
        "type": Term("admin", "admin|user|guest"),
        "items": EachLike("cat", 2)
			},
		})

This example will result in a response body from the mock server that looks like:

{
  "response": {
    "name": "Billy",
    "type": "admin",
    "items": [
      "cat",
      "cat"
    ]
  }
}

See the examples in the dsl package and the matcher tests (https://github.com/pact-foundation/pact-go/v2/blob/master/dsl/matcher_test.go) for more matching examples.

NOTE: You will need to use valid Ruby regular expressions (http://ruby-doc.org/core-2.1.5/Regexp.html) and double escape backslashes.

Read more about flexible matching (https://github.com/pact-foundation/pact-ruby/wiki/Regular-expressions-and-type-matching-with-Pact.

Provider Tests

Provider side Pact testing, involves verifying that the contract - the Pact file - can be satisfied by the Provider.

A typical Provider side test would like something like:

func TestProvider_PactContract(t *testing.T) {
  // Create Pact
	pact := Pact{}
	go startMyAPI("http://localhost:8000")

	pact.VerifyProvider(types.VerifyRequest{
		ProviderBaseURL:        "http://localhost:8000",
		PactURLs:               []string{"./pacts/my_consumer-my_provider.json"},
		ProviderStatesSetupURL: "http://localhost:8000/setup",
	})
}

The `VerifyProvider` will handle all verifications, treating them as subtests and giving you granular test reporting. If you don't like this behaviour, you may call `VerifyProviderRaw` directly and handle the errors manually.

Note that `PactURLs` may be a list of local pact files or remote based urls (possibly from a Pact Broker - http://docs.pact.io/documentation/sharings_pacts.html).

Pact reads the specified pact files (from remote or local sources) and replays the interactions against a running Provider. If all of the interactions are met we can say that both sides of the contract are satisfied and the test passes.

Provider Verification

When validating a Provider, you have 3 options to provide the Pact files:

1. Use "PactURLs" to specify the exact set of pacts to be replayed:

response, err = pact.VerifyProvider(types.VerifyRequest{
	ProviderBaseURL:        "http://myproviderhost",
	PactURLs:               []string{"http://broker/pacts/provider/them/consumer/me/latest/dev"},
	ProviderStatesSetupURL: "http://myproviderhost/setup",
	BrokerUsername:         os.Getenv("PACT_BROKER_USERNAME"),
	BrokerPassword:         os.Getenv("PACT_BROKER_PASSWORD"),
	BrokerToken:            os.Getenv("PACT_BROKER_TOKEN"),
})

2. Use "PactBroker" to automatically find all of the latest consumers:

response, err = pact.VerifyProvider(types.VerifyRequest{
	ProviderBaseURL:        "http://myproviderhost",
	BrokerURL:              brokerHost,
	ProviderStatesSetupURL: "http://myproviderhost/setup",
	BrokerUsername:         os.Getenv("PACT_BROKER_USERNAME"),
	BrokerPassword:         os.Getenv("PACT_BROKER_PASSWORD"),
	BrokerToken:            os.Getenv("PACT_BROKER_TOKEN"),
})

3. Use "PactBroker" and "Tags" to automatically find all of the latest consumers:

response, err = pact.VerifyProvider(types.VerifyRequest{
	ProviderBaseURL:        "http://myproviderhost",
	BrokerURL:              brokerHost,
	Tags:                   []string{"master", "sit4"},
	ProviderStatesSetupURL: "http://myproviderhost/setup",
	BrokerUsername:         os.Getenv("PACT_BROKER_USERNAME"),
	BrokerPassword:         os.Getenv("PACT_BROKER_PASSWORD"),
	BrokerToken:            os.Getenv("PACT_BROKER_TOKEN"),
})

Options 2 and 3 are particularly useful when you want to validate that your Provider is able to meet the contracts of what's in Production and also the latest in development.

See this [article](http://rea.tech/enter-the-pact-matrix-or-how-to-decouple-the-release-cycles-of-your-microservices/) for more on this strategy.

Provider States

Each interaction in a pact should be verified in isolation, with no context maintained from the previous interactions. So how do you test a request that requires data to exist on the provider? Provider states are how you achieve this using Pact.

Provider states also allow the consumer to make the same request with different expected responses (e.g. different response codes, or the same resource with a different subset of data).

States are configured on the consumer side when you issue a dsl.Given() clause with a corresponding request/response pair.

Configuring the provider is a little more involved, and (currently) requires running an API endpoint to configure any [provider states](http://docs.pact.io/documentation/provider_states.html) during the verification process. The option you must provide to the dsl.VerifyRequest is:

ProviderStatesSetupURL: 	POST URL to set the provider state (see types.ProviderState)

An example route using the standard Go http package might look like this:

// Handle a request from the verifier to configure a provider state (ProviderStatesSetupURL)
mux.HandleFunc("/setup", func(w http.ResponseWriter, req *http.Request) {
  w.Header().Add("Content-Type", "application/json")

  // Retrieve the Provider State
  var state types.ProviderState

  body, _ := io.ReadAll(req.Body)
  req.Body.Close()
  json.Unmarshal(body, &state)

  // Configure database for different states
  if state.State == "User A exists" {
    svc.userDatabase = aExists
  } else if state.State == "User A is unauthorized" {
    svc.userDatabase = aUnauthorized
  } else {
    svc.userDatabase = aDoesNotExist
  }
})

See the examples or read more at http://docs.pact.io/documentation/provider_states.html.

Publishing Pacts to a Broker and Tagging Pacts

See the Pact Broker (http://docs.pact.io/documentation/sharings_pacts.html) documentation for more details on the Broker and this article (http://rea.tech/enter-the-pact-matrix-or-how-to-decouple-the-release-cycles-of-your-microservices/) on how to make it work for you.

Publishing using Go code:

pact.PublishPacts(types.PublishRequest{
	PactBroker:             "http://pactbroker:8000",
	PactURLs:               []string{"./pacts/my_consumer-my_provider.json"},
	ConsumerVersion:        "1.0.0",
	Tags:                   []string{"master", "dev"},
})

Publishing from the CLI:

Use a cURL request like the following to PUT the pact to the right location, specifying your consumer name, provider name and consumer version.

curl -v -XPUT \-H "Content-Type: application/json" \
-d@spec/pacts/a_consumer-a_provider.json \
http://your-pact-broker/pacts/provider/A%20Provider/consumer/A%20Consumer/version/1.0.0

Using the Pact Broker with Basic authentication

The following flags are required to use basic authentication when publishing or retrieving Pact files to/from a Pact Broker:

BrokerUsername	uername for Pact Broker basic authentication
BrokerPassword	password for Pact Broker basic authentication

Output Logging

Pact Go uses a simple log utility (logutils - https://github.com/hashicorp/logutils) to filter log messages. The CLI already contains flags to manage this, should you want to control log level in your tests, you can set it like so:

pact := Pact{
  ...
	LogLevel: "DEBUG", // One of DEBUG, INFO, ERROR, NONE
}