Godog

The API is likely to change a few times before we reach 1.0.0

Please read the full README, you may find it very useful. And do not forget to peek into the Release Notes and the CHANGELOG from time to time.

Package godog is the official Cucumber BDD framework for Golang, it merges specification and test documentation into one cohesive whole, using Gherkin formatted scenarios in the format of Given, When, Then.

The project was inspired by behat and cucumber.

Why Godog/Cucumber

A single source of truth

Godog merges specification and test documentation into one cohesive whole.

Living documentation

Because they're automatically tested by Godog, your specifications are always bang up-to-date.

Focus on the customer

Business and IT don't always understand each other. Godog's executable specifications encourage closer collaboration, helping teams keep the business goal in mind at all times.

Less rework

When automated testing is this much fun, teams can easily protect themselves from costly regressions.

Read more

• Behaviour-Driven Development
• Gherkin Reference

Contributions

Godog is a community driven Open Source Project within the Cucumber organization. We welcome contributions from everyone, and we're ready to support you if you have the enthusiasm to contribute.

See the contributing guide for more detail on how to get started.

See the releasing guide for release flow details.

Getting help

We have a community Slack where you can chat with other users, developers, and BDD practitioners.

Here are some useful channels to try:

• #help-godog - General Godog Adoption Help
• #committers-go - Golang focused Cucumber Contributors
• #committers - General Cucumber Contributors

Examples

You can find a few examples here.

Note that if you want to execute any of the examples and have the Git repository checked out in the $GOPATH, you need to use: GO111MODULE=off. Issue for reference.

Godogs

The following example can be found here.

Step 1 - Setup a go module

Create a new go module named godogs in your go workspace by running mkdir godogs

From now on, use godogs as your working directory by running cd godogs

Initiate the go module inside the godogs directory by running go mod init godogs

Step 2 - Create gherkin feature

Imagine we have a godog cart to serve godogs for lunch.

First of all, we describe our feature in plain text:

Feature: eat godogs
  In order to be happy
  As a hungry gopher
  I need to be able to eat godogs

  Scenario: Eat 5 out of 12
    Given there are 12 godogs
    When I eat 5
    Then there should be 7 remaining

Run vim features/godogs.feature and add the text above into the vim editor and save the file.

Step 3 - Create godog step definitions

NOTE: Same as go test, godog respects package level isolation. All your step definitions should be in your tested package root directory. In this case: godogs.

Create and copy the step definitions below into a new file by running vim godogs_test.go:

package main

import "github.com/cucumber/godog"

func iEat(arg1 int) error {
        return godog.ErrPending
}

func thereAreGodogs(arg1 int) error {
        return godog.ErrPending
}

func thereShouldBeRemaining(arg1 int) error {
        return godog.ErrPending
}

func InitializeScenario(ctx *godog.ScenarioContext) {
        ctx.Step(`^there are (\d+) godogs$`, thereAreGodogs)
        ctx.Step(`^I eat (\d+)$`, iEat)
        ctx.Step(`^there should be (\d+) remaining$`, thereShouldBeRemaining)
}

Alternatively, you can also specify the keyword (Given, When, Then...) when creating the step definitions:

func InitializeScenario(ctx *godog.ScenarioContext) {
        ctx.Given(`^there are (\d+) godogs$`, thereAreGodogs)
        ctx.When(`^I eat (\d+)$`, iEat)
        ctx.Then(`^there should be (\d+) remaining$`, thereShouldBeRemaining)
}

Our module should now look like this:

godogs
- features
  - godogs.feature
- go.mod
- go.sum
- godogs_test.go

Run go test in the godogs directory to run the steps you have defined. You should now see that the scenario runs with a warning stating there are no tests to run.

testing: warning: no tests to run
PASS
ok      godogs  0.225s

By adding some logic to these steps, you will be able to thoroughly test the feature you just defined.

Step 4 - Create the main program to test

Let's keep it simple by only requiring an amount of godogs for now.

Create and copy the code below into a new file by running vim godogs.go

package main

// Godogs available to eat
var Godogs int

func main() { /* usual main func */ }

Our module should now look like this:

godogs
- features
  - godogs.feature
- go.mod
- go.sum
- godogs.go
- godogs_test.go

Step 5 - Add some logic to the step definitions

Now lets implement our step definitions to test our feature requirements.

Replace the contents of godogs_test.go with the code below by running vim godogs_test.go.

package main

import (
  "context"
  "errors"
  "fmt"
  "testing"

  "github.com/cucumber/godog"
)

// godogsCtxKey is the key used to store the available godogs in the context.Context.
type godogsCtxKey struct{}

func thereAreGodogs(ctx context.Context, available int) (context.Context, error) {
  return context.WithValue(ctx, godogsCtxKey{}, available), nil
}

func iEat(ctx context.Context, num int) (context.Context, error) {
  available, ok := ctx.Value(godogsCtxKey{}).(int)
  if !ok {
    return ctx, errors.New("there are no godogs available")
  }

  if available < num {
    return ctx, fmt.Errorf("you cannot eat %d godogs, there are %d available", num, available)
  }

  available -= num

  return context.WithValue(ctx, godogsCtxKey{}, available), nil
}

func thereShouldBeRemaining(ctx context.Context, remaining int) error {
  available, ok := ctx.Value(godogsCtxKey{}).(int)
  if !ok {
    return errors.New("there are no godogs available")
  }

  if available != remaining {
    return fmt.Errorf("expected %d godogs to be remaining, but there is %d", remaining, available)
  }

  return nil
}

func TestFeatures(t *testing.T) {
  suite := godog.TestSuite{
    ScenarioInitializer: InitializeScenario,
    Options: &godog.Options{
      Format:   "pretty",
      Paths:    []string{"features"},
      TestingT: t, // Testing instance that will run subtests.
    },
  }

  if suite.Run() != 0 {
    t.Fatal("non-zero status returned, failed to run feature tests")
  }
}

func InitializeScenario(sc *godog.ScenarioContext) {
  sc.Step(`^there are (\d+) godogs$`, thereAreGodogs)
  sc.Step(`^I eat (\d+)$`, iEat)
  sc.Step(`^there should be (\d+) remaining$`, thereShouldBeRemaining)
}

In this example, we are using context.Context to pass the state between the steps. Every scenario starts with an empty context and then steps and hooks can add relevant information to it. Instrumented context is chained through the steps and hooks and is safe to use when multiple scenarios are running concurrently.

When you run godog again with go test -v godogs_test.go, you should see a passing run:

=== RUN   TestFeatures
Feature: eat godogs
  In order to be happy
  As a hungry gopher
  I need to be able to eat godogs
=== RUN   TestFeatures/Eat_5_out_of_12

  Scenario: Eat 5 out of 12          # features/godogs.feature:6
    Given there are 12 godogs        # godog_test.go:15 -> command-line-arguments.thereAreGodogs
    When I eat 5                     # godog_test.go:19 -> command-line-arguments.iEat
    Then there should be 7 remaining # godog_test.go:34 -> command-line-arguments.thereShouldBeRemaining

1 scenarios (1 passed)
3 steps (3 passed)
279.917µs
--- PASS: TestFeatures (0.00s)
    --- PASS: TestFeatures/Eat_5_out_of_12 (0.00s)
PASS
ok      command-line-arguments  0.164s

You may hook to ScenarioContext Before event in order to reset or pre-seed the application state before each scenario. You may hook into more events, like sc.StepContext() After to print all state in case of an error. Or BeforeSuite to prepare a database.

By now, you should have figured out, how to use godog. Another piece of advice is to make steps orthogonal, small and simple to read for a user. Whether the user is a dumb website user or an API developer, who may understand a little more technical context - it should target that user.

When steps are orthogonal and small, you can combine them just like you do with Unix tools. Look how to simplify or remove ones, which can be composed.

TestFeatures acts as a regular Go test, so you can leverage your IDE facilities to run and debug it.

Code of Conduct

Everyone interacting in this codebase and issue tracker is expected to follow the Cucumber code of conduct.

References and Tutorials

• cucumber-html-reporter, may be used in order to generate html reports together with cucumber output formatter. See the following docker image for usage details.
• how to use godog by semaphoreci
• see examples
• see extension AssistDog, which may have useful gherkin.DataTable transformations or comparison methods for assertions.

Documentation

See pkg documentation for general API details. See Circle Config for supported go versions. See godog -h for general command options.

See implementation examples:

• rest API server
• rest API with Database
• godogs

FAQ

Running Godog with go test

You may integrate running godog in your go test command.

Subtests of *testing.T

You can run test suite using go Subtests. In this case it is not necessary to have godog command installed. See the following example.

package main_test

import (
	"testing"

	"github.com/cucumber/godog"
)

func TestFeatures(t *testing.T) {
  suite := godog.TestSuite{
    ScenarioInitializer: func(s *godog.ScenarioContext) {
      // Add step definitions here.
    },
    Options: &godog.Options{
      Format:   "pretty",
      Paths:    []string{"features"},
      TestingT: t, // Testing instance that will run subtests.
    },
  }

  if suite.Run() != 0 {
    t.Fatal("non-zero status returned, failed to run feature tests")
  }
}

Then you can run suite.

go test -test.v -test.run ^TestFeatures$

Or a particular scenario.

go test -test.v -test.run ^TestFeatures$/^my_scenario$

TestMain

You can run test suite using go TestMain func available since go 1.4. In this case it is not necessary to have godog command installed. See the following examples.

The following example binds godog flags with specified prefix godog in order to prevent flag collisions.

package main

import (
	"os"
	"testing"

	"github.com/cucumber/godog"
	"github.com/cucumber/godog/colors"
	"github.com/spf13/pflag" // godog v0.11.0 and later
)

var opts = godog.Options{
	Output: colors.Colored(os.Stdout),
	Format: "progress", // can define default values
}

func init() {
	godog.BindFlags("godog.", pflag.CommandLine, &opts) // godog v0.10.0 and earlier
	godog.BindCommandLineFlags("godog.", &opts)        // godog v0.11.0 and later
}

func TestMain(m *testing.M) {
	pflag.Parse()
	opts.Paths = pflag.Args()

	status := godog.TestSuite{
		Name: "godogs",
		TestSuiteInitializer: InitializeTestSuite,
		ScenarioInitializer:  InitializeScenario,
		Options: &opts,
	}.Run()

	// Optional: Run `testing` package's logic besides godog.
	if st := m.Run(); st > status {
		status = st
	}

	os.Exit(status)
}

Then you may run tests with by specifying flags in order to filter features.

go test -v --godog.random --godog.tags=wip
go test -v --godog.format=pretty --godog.random -race -coverprofile=coverage.txt -covermode=atomic

The following example does not bind godog flags, instead manually configuring needed options.

func TestMain(m *testing.M) {
	opts := godog.Options{
		Format:    "progress",
		Paths:     []string{"features"},
		Randomize: time.Now().UTC().UnixNano(), // randomize scenario execution order
	}

	status := godog.TestSuite{
		Name: "godogs",
		TestSuiteInitializer: InitializeTestSuite,
		ScenarioInitializer:  InitializeScenario,
		Options: &opts,
	}.Run()

	// Optional: Run `testing` package's logic besides godog.
	if st := m.Run(); st > status {
		status = st
	}

	os.Exit(status)
}

You can even go one step further and reuse go test flags, like verbose mode in order to switch godog format. See the following example:

func TestMain(m *testing.M) {
	format := "progress"
	for _, arg := range os.Args[1:] {
		if arg == "-test.v=true" { // go test transforms -v option
			format = "pretty"
			break
		}
	}

	opts := godog.Options{
		Format: format,
		Paths:     []string{"features"},
	}

	status := godog.TestSuite{
		Name: "godogs",
		TestSuiteInitializer: InitializeTestSuite,
		ScenarioInitializer:  InitializeScenario,
		Options: &opts,
	}.Run()

	// Optional: Run `testing` package's logic besides godog.
	if st := m.Run(); st > status {
		status = st
	}

	os.Exit(status)
}

Now when running go test -v it will use pretty format.

Tags

If you want to filter scenarios by tags, you can use the -t= or --tags= where `` is one of the following:

• @wip - run all scenarios with wip tag
• ~@wip - exclude all scenarios with wip tag
• @wip && ~@new - run wip scenarios, but exclude new
• @wip,@undone - run wip or undone scenarios

Using assertion packages like testify with Godog

A more extensive example can be found here.

func thereShouldBeRemaining(remaining int) error {
	return assertExpectedAndActual(
		assert.Equal, Godogs, remaining,
		"Expected %d godogs to be remaining, but there is %d", remaining, Godogs,
	)
}

// assertExpectedAndActual is a helper function to allow the step function to call
// assertion functions where you want to compare an expected and an actual value.
func assertExpectedAndActual(a expectedAndActualAssertion, expected, actual interface{}, msgAndArgs ...interface{}) error {
	var t asserter
	a(&t, expected, actual, msgAndArgs...)
	return t.err
}

type expectedAndActualAssertion func(t assert.TestingT, expected, actual interface{}, msgAndArgs ...interface{}) bool

// asserter is used to be able to retrieve the error reported by the called assertion
type asserter struct {
	err error
}

// Errorf is used by the called assertion to report an error
func (a *asserter) Errorf(format string, args ...interface{}) {
	a.err = fmt.Errorf(format, args...)
}

Embeds

If you're looking to compile your test binary in advance of running, you can compile the feature files into the binary via go:embed:

//go:embed features/*
var features embed.FS

var opts = godog.Options{
	Paths: []string{"features"},
	FS:    features,
}

Now, the test binary can be compiled with all feature files embedded, and can be ran independently from the feature files:

> go test -c ./test/integration/integration_test.go
> mv integration.test /some/random/dir
> cd /some/random/dir
> ./integration.test

NOTE: godog.Options.FS is as fs.FS, so custom filesystem loaders can be used.

CLI Mode

NOTE: The godog CLI has been deprecated. It is recommended to use go test instead.

Another way to use godog is to run it in CLI mode.

In this mode godog CLI will use go under the hood to compile and run your test suite.

Godog does not intervene with the standard go test command behavior. You can leverage both frameworks to functionally test your application while maintaining all test related source code in _test.go files.

Godog acts similar compared to go test command, by using go compiler and linker tool in order to produce test executable. Godog contexts need to be exported the same way as Test functions for go tests. Note, that if you use godog command tool, it will use go executable to determine compiler and linker.

Install

go install github.com/cucumber/godog/cmd/godog@latest

Adding @v0.12.0 will install v0.12.0 specifically instead of master.

With go version prior to 1.17, use go get github.com/cucumber/godog/cmd/godog@v0.12.0. Running within the $GOPATH, you would also need to set GO111MODULE=on, like this:

GO111MODULE=on go get github.com/cucumber/godog/cmd/godog@v0.12.0

Configure common options for godog CLI

There are no global options or configuration files. Alias your common or project based commands: alias godog-wip="godog --format=progress --tags=@wip"

Concurrency

When concurrency is configured in options, godog will execute the scenarios concurrently, which is supported by all supplied formatters.

In order to support concurrency well, you should reset the state and isolate each scenario. They should not share any state. It is suggested to run the suite concurrently in order to make sure there is no state corruption or race conditions in the application.

It is also useful to randomize the order of scenario execution, which you can now do with --random command option or godog.Options.Randomize setting.

Building your own custom formatter

A simple example can be found here.

License

Godog and Gherkin are licensed under the MIT and developed as a part of the cucumber project