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Godog

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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.

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.

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

Install

go get github.com/cucumber/godog/cmd/[email protected]

Adding @v0.10.0 will install v0.10.0 specifically instead of master.

Running within the $GOPATH, you would also need to set GO111MODULE=on, like this:

GO111MODULE=on go get github.com/cucumber/godog/cmd/[email protected]

Contributions

Godog is a community driven Open Source Project within the Cucumber organization, it is maintained by a handfull of developers, but we appreciate contributions from everyone.

If you are interested in developing Godog, we suggest you to visit one of our slack channels.

Feel free to open a pull request. Note, if you wish to contribute larger changes or an extension to the exported methods or types, please open an issue before and visit us in slack to discuss the changes.

Reach out to the community on our Cucumber Slack Community. Join here.

Popular Cucumber Slack channels for Godog:

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

Given we create a new go module godogs in your normal go workspace. - mkdir godogs

From now on, this is our work directory - cd godogs

Initiate the go module - go mod init godogs

Step 2 - Install godog

Install the godog binary - go get github.com/cucumber/godog/cmd/godog

Step 3 - Create gherkin feature

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

First of all, we describe our feature in plain text - vim features/godogs.feature

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

Step 4 - 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.

If we run godog inside the module: - godog

You should see that the steps are undefined:

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          # features/godogs.feature:6
    Given there are 12 godogs
    When I eat 5
    Then there should be 7 remaining

1 scenarios (1 undefined)
3 steps (3 undefined)
220.129µs

You can implement step definitions for undefined steps with these snippets:

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

Create and copy the step definitions into a new file - 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(`^I eat (\d+)$`, iEat)
        ctx.Step(`^there are (\d+) godogs$`, thereAreGodogs)
        ctx.Step(`^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 godog again - godog

You should now see that the scenario is pending with one step pending and two steps skipped:

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          # features/godogs.feature:6
    Given there are 12 godogs        # godogs_test.go:10 -> thereAreGodogs
      TODO: write pending definition
    When I eat 5                     # godogs_test.go:6 -> iEat
    Then there should be 7 remaining # godogs_test.go:14 -> thereShouldBeRemaining

1 scenarios (1 pending)
3 steps (1 pending, 2 skipped)
282.123µs

You may change return godog.ErrPending to return nil in the three step definitions and the scenario will pass successfully.

Step 5 - Create the main program to test

We only need a number of godogs for now. Lets keep it simple.

Create and copy the code into a new file - 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 6 - Add some logic to the step defintions

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

Replace the contents of godogs_test.go with the code below - vim godogs_test.go

package main

import (
	"fmt"

	"github.com/cucumber/godog"
)

func thereAreGodogs(available int) error {
	Godogs = available
	return nil
}

func iEat(num int) error {
	if Godogs < num {
		return fmt.Errorf("you cannot eat %d godogs, there are %d available", num, Godogs)
	}
	Godogs -= num
	return nil
}

func thereShouldBeRemaining(remaining int) error {
	if Godogs != remaining {
		return fmt.Errorf("expected %d godogs to be remaining, but there is %d", remaining, Godogs)
	}
	return nil
}

func InitializeTestSuite(ctx *godog.TestSuiteContext) {
	ctx.BeforeSuite(func() { Godogs = 0 })
}

func InitializeScenario(ctx *godog.ScenarioContext) {
	ctx.BeforeScenario(func(*godog.Scenario) {
		Godogs = 0 // clean the state before every scenario
	})

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

When you run godog again - godog

You should see a passing run:

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          # features/godogs.feature:6
    Given there are 12 godogs        # godogs_test.go:10 -> thereAreGodogs
    When I eat 5                     # godogs_test.go:14 -> iEat
    Then there should be 7 remaining # godogs_test.go:22 -> thereShouldBeRemaining

1 scenarios (1 passed)
3 steps (3 passed)
258.302µs

We have hooked to BeforeScenario event in order to reset the application state before each scenario. You may hook into more events, like AfterStep 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 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.

Code of Conduct

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

References and Tutorials

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:

FAQ

Running Godog with go test

You may integrate running godog in your go test command. You can run it 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.

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

func init() {
	// godog v0.10.0 and earlier
	godog.BindFlags("godog.", flag.CommandLine, &opts)

	// godog v0.11.0-rc1 (latest)
	godog.BindCommandLineFlags("godog.", &opts)
}

func TestMain(m *testing.M) {
	flag.Parse()
	opts.Paths = flag.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=<expression> or --tags=<expression> where <expression> is one of the following:

  • @wip - run all scenarios with wip tag
  • [email protected] - exclude all scenarios with wip tag
  • @wip && [email protected] - 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...)
}

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 [email protected]"

Testing browser interactions

godog does not come with builtin packages to connect to the browser. You may want to look at selenium and probably phantomjs. See also the following components:

  1. browsersteps - provides basic context steps to start selenium and navigate browser content.
  2. You may wish to have goquery in order to work with HTML responses like with JQuery.

Concurrency

When concurrency is configured in options, godog will execute the scenarios concurrently, which is support 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.

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


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