Pact Go

Golang version of Pact. 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.

Introduction

From the Pact website:

The Pact family of frameworks provide support for Consumer Driven Contracts testing.

A Contract is a collection of agreements between a client (Consumer) and an API (Provider) that describes the interactions that can take place between them.

Consumer Driven Contracts is a pattern that drives the development of the Provider from its Consumers point of view.

Pact is a testing tool that guarantees those Contracts are satisfied.

Read Getting started with Pact for more information on how to get going.

Pact Go implements Pact Specification v2, including flexible matching.

Installation

Download one of the zipped release distributions for your OS.
Unzip the package into a known location, and ensuring the pact-go binary is on the PATH, next to the pact folder.
Run pact-go to see what options are available.
Run go get -d github.com/pact-foundation/pact-go to install the source packages

Running

Pact Go runs a two-step process:

Run pact-go daemon in a separate process/shell. The Consumer and Provider DSLs communicate over a local (RPC) connection, and is transparent to clients.
Create your Pact Consumer/Provider Tests. It defaults to run on port 6666.

NOTE: The daemon is thread safe and it is normal to leave it running for long periods (e.g. on a CI server).

Consumer

We'll run through a simple example to get an understanding the concepts:

Start the daemon with ./pact-go daemon.
go get github.com/pact-foundation/pact-go
cd $GOPATH/src/github.com/pact-foundation/pact-go/examples/
go test -v -run TestConsumer.

The simple example looks like this:

package main

import (
	"fmt"
	"log"
	"net/http"
	"strings"
	"testing"

	"github.com/pact-foundation/pact-go/dsl"
)

// Example Pact: How to run me!
// 1. Start the daemon with `./pact-go daemon`
// 2. cd <pact-go>/examples
// 3. go test -v -run TestConsumer
func TestConsumer(t *testing.T) {

	// Create Pact connecting to local Daemon
	pact := &dsl.Pact{
		Port:     6666, // Ensure this port matches the daemon port!
		Consumer: "MyConsumer",
		Provider: "MyProvider",
		Host:     "localhost",
	}
	defer pact.Teardown()

	// Pass in test case
	var test = func() error {
		u := fmt.Sprintf("http://localhost:%d/foobar", pact.Server.Port)
		req, err := http.NewRequest("GET", u, strings.NewReader(`{"s":"foo"}`))

		// NOTE: by default, request bodies are expected to be sent with a Content-Type
		// of application/json. If you don't explicitly set the content-type, you
		// will get a mismatch during Verification.
		req.Header.Set("Content-Type", "application/json")
		if err != nil {
			return err
		}
		if _, err = http.DefaultClient.Do(req); err != nil {
			return err
		}

		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:    "/foobar",
			Headers: map[string]string{"Content-Type": "application/json"},
			Body:    `{"s":"foo"}`,
		}).
		WillRespondWith(dsl.Response{
			Status:  200,
			Headers: map[string]string{"Content-Type": "application/json"},
			Body:    `{"s":"bar"}`,
		})

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

Matching (Consumer Tests)

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.

dsl.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.
dsl.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.
dsl.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.

Example:

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

colour := Term("red", "red|green|blue")

match := EachLike(
              EachLike(
                         fmt.Sprintf(`{
                             "size": 10,
                             "colour": %s,
                             "tag": [["jumper", "shirt]]
                         }`, colour)
              1),
         1))

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

[
  [
    {
      "size": 10,
      "colour": "red",
      "tag": [
        [
          "jumper",
          "shirt"
        ],
        [
          "jumper",
          "shirt"
        ]
      ]
    }
  ]
]

See the matcher tests for more matching examples.

NOTE: One caveat to note, is that you will need to use valid Ruby regular expressions and double escape backslashes.

Provider

Start the daemon with ./pact-go daemon.
go get github.com/pact-foundation/pact-go
cd $GOPATH/src/github.com/pact-foundation/pact-go/examples/
go test -v -run TestProvider.

Here is the Provider test process broker down:

Start your Provider API:

You need to be able to first start your API in the background as part of your tests before you can run the verification process. Here we create startServer which can be started in its own goroutine:

func startServer() {
  mux := http.NewServeMux()
  lastName := "billy"

  mux.HandleFunc("/foobar", func(w http.ResponseWriter, req *http.Request) {
    w.Header().Add("Content-Type", "application/json")
    fmt.Fprintf(w, fmt.Sprintf(`{"lastName":"%s"}`, lastName))

    // Break the API by replacing the above and uncommenting one of these
    // w.WriteHeader(http.StatusUnauthorized)
    // fmt.Fprintf(w, `{"s":"baz"}`)
  })

  // This function handles state requests for a particular test
  // In this case, we ensure that the user being requested is available
  // before the Verification process invokes the API.
  mux.HandleFunc("/setup", func(w http.ResponseWriter, req *http.Request) {
    var s *types.ProviderState
    decoder := json.NewDecoder(req.Body)
    decoder.Decode(&s)
    if s.State == "User foo exists" {
      lastName = "bar"
    }

    w.Header().Add("Content-Type", "application/json")
  })
  go http.ListenAndServe(":8000", mux)
}

Note that the server has a /setup endpoint that is given a types.ProviderState and allows the verifier to setup any provider states before each test is run.

Verify provider API

You can now tell Pact to read in your Pact files and verify that your API will satisfy the requirements of each of your known consumers:

func TestProvider(t *testing.T) {

  // Create Pact connecting to local Daemon
  pact := &dsl.Pact{
    Port:     6666, // Ensure this port matches the daemon port!
    Consumer: "MyConsumer",
    Provider: "MyProvider",
  }

  // Start provider API in the background
  go startServer()

  // Verify the Provider with local Pact Files
  pact.VerifyProvider(t, types.VerifyRequest{
    ProviderBaseURL:        "http://localhost:8000",
    PactURLs:               []string{filepath.ToSlash(fmt.Sprintf("%s/myconsumer-myprovider.json", pactDir))},
    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 (e.g. from a Pact Broker).

See the Skip()'ed integration tests for a more complete E2E example.

Provider Verification

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

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

pact.VerifyProvider(t, 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"),
})

Use PactBroker to automatically find all of the latest consumers:

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

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

pact.VerifyProvider(t, types.VerifyRequest{
	ProviderBaseURL:        "http://myproviderhost",
	BrokerURL:              "http://brokerHost",
	Tags:                   []string{"latest", "sit4"},
	ProviderStatesSetupURL: "http://myproviderhost/setup",
	BrokerUsername:         os.Getenv("PACT_BROKER_USERNAME"),
	BrokerPassword:         os.Getenv("PACT_BROKER_PASSWORD"),
})

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 for more on this strategy.

For more on provider states, refer to http://docs.pact.io/documentation/provider_states.html.

API with Authorization

Sometimes you may need to add things to the requests that can't be persisted in a pact file. Examples of these would be authentication tokens, which have a small life span. e.g. an OAuth bearer token: Authorization: Bearer 0b79bab50daca910b000d4f1a2b675d604257e42.

For this case, we have a facility that should be carefully used during verification - the ability to specificy custom headers to be sent during provider verification. The property to achieve this is CustomProviderHeaders.

For example, to have an Authorization header sent as part of the verification request, modify the VerifyRequest parameter as per below:

  pact.VerifyProvider(t, types.VerifyRequest{
    ...
    CustomProviderHeaders:  []string{"Authorization: Bearer 0b79bab50daca910b000d4f1a2b675d604257e42"},
  })

As you can see, this is your opportunity to modify\add to headers being sent to the Provider API, for example to create a valid time-bound token.

Important Note: You should only use this feature for things that can not be persisted in the pact file. By modifying the request, you are potentially modifying the contract from the consumer tests!

Publishing pacts to a Pact Broker and Tagging Pacts

See the Pact Broker documentation for more details on the Broker and this article on how to make it work for you.

Publishing from Go code

p := Publisher{}
err := p.Publish(types.PublishRequest{
	PactURLs:	[]string{"./pacts/my_consumer-my_provider.json"},
	PactBroker:	"http://pactbroker:8000",
	ConsumerVersion: "1.0.0",
	Tags:		[]string{"latest", "dev"},
})

Publishing Provider Verification Results to a Pact Broker

If you're using a Pact Broker (e.g. a hosted one at pact.dius.com.au), you can publish your verification results so that consumers can query if they are safe to release.

It looks like this:

You need to specify the following:

PublishVerificationResults: true,
ProviderVersion:            "1.0.0",

NOTE: You need to be already pulling pacts from the broker for this feature to work.

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 \
  -X PUT \
  -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 - the username for Pact Broker basic authentication.
BrokerPassword - the password for Pact Broker basic authentication.

Troubleshooting

Splitting tests across multiple files

Pact tests tend to be quite long, due to the need to be specific about request/response payloads. Often times it is nicer to be able to split your tests across multiple files for manageability.

You have two options to achieve this feat:

Set PactFileWriteMode to "merge" when creating a Pact struct:

This will allow you to have multiple independent tests for a given Consumer-Provider pair, without it clobbering previous interactions.

See this PR for background.

NOTE: If using this approach, you must be careful to clear out existing pact files (e.g. rm ./pacts/*.json) before you run tests to ensure you don't have left over requests that are no longer relevent.
Create a Pact test helper to orchestrate the setup and teardown of the mock service for multiple tests.

In larger test bases, this can reduce test suite time and the amount of code you have to manage.

See the JS example and related issue for more.

Output Logging

Pact Go uses a simple log utility (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
}

Examples

There is a number of examples we use as end-to-end integration test prior to releasing a new binary, including publishing to a Pact Broker. You can run them all by running make pact in the project root, or manually (after starting the daemon) as follows:

cd $GOPATH/src/github.com/pact-foundation/pact-go/examples
export PACT_INTEGRATED_TESTS=1
export PACT_BROKER_USERNAME="dXfltyFMgNOFZAxr8io9wJ37iUpY42M"
export PACT_BROKER_PASSWORD="O5AIZWxelWbLvqMd8PkAVycBJh2Psyg1"
export PACT_BROKER_HOST="https://test.pact.dius.com.au"

Once these variables have been exported, cd into one of the directories containing a test and run go test -v .:

Contact

Twitter: @pact_up
Stack Overflow: stackoverflow.com/questions/tagged/pact
Gitter: https://gitter.im/realestate-com-au/pact
Gophers #pact Slack channel

Documentation

Additional documentation can be found at the main Pact website and in the Pact Wiki.

Troubleshooting

See TROUBLESHOOTING for some helpful tips/tricks.

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.

Name		Name	Last commit message	Last commit date
Latest commit History 266 Commits
.github		.github
command		command
daemon		daemon
dsl		dsl
examples		examples
scripts		scripts
types		types
utils		utils
vendor		vendor
.codeclimate.yml		.codeclimate.yml
.gitignore		.gitignore
CHANGELOG.md		CHANGELOG.md
CONTRIBUTING.md		CONTRIBUTING.md
Dockerfile		Dockerfile
LICENSE		LICENSE
Makefile		Makefile
README.md		README.md
RELEASING.md		RELEASING.md
appveyor.yml		appveyor.yml
doc.go		doc.go
docker-compose.yml		docker-compose.yml
main.go		main.go
vendor.yml		vendor.yml
wercker.yml		wercker.yml

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Pact Go

Introduction

Table of Contents

Installation

Running

Consumer

Matching (Consumer Tests)

Provider

Provider Verification

API with Authorization

Publishing pacts to a Pact Broker and Tagging Pacts

Publishing from Go code

Publishing Provider Verification Results to a Pact Broker

Publishing from the CLI

Using the Pact Broker with Basic authentication

Troubleshooting

Splitting tests across multiple files

Output Logging

Examples

Contact

Documentation

Troubleshooting

Roadmap

Contributing

About

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Pact Go

Introduction

Table of Contents

Installation

Running

Consumer

Matching (Consumer Tests)

Provider

Provider Verification

API with Authorization

Publishing pacts to a Pact Broker and Tagging Pacts

Publishing from Go code

Publishing Provider Verification Results to a Pact Broker

Publishing from the CLI

Using the Pact Broker with Basic authentication

Troubleshooting

Splitting tests across multiple files

Output Logging

Examples

Contact

Documentation

Troubleshooting

Roadmap

Contributing

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