Gherkin Sintax

Gherkin uses a set of special keywords to give structure and meaning to executable specifications.

Most lines in a Gherkin document start with one of the keywords.

Comments are only permitted at the start of a new line, anywhere in the feature file. They begin with zero or more spaces, followed by a hash sign (#) and some text.

Block comments are currently not supported by Gherkin.

Either spaces or tabs may be used for indentation. The recommended indentation level is two spaces. Here is an example:

Feature: Guess the word

  # The first example has two steps
  Scenario: Maker starts a game
    When the Maker starts a game
    Then the Maker waits for a Breaker to join

  # The second example has three steps
  Scenario: Breaker joins a game
    Given the Maker has started a game with the word "silky"
    When the Breaker joins the Maker's game
    Then the Breaker must guess a word with 5 characters

The trailing portion (after the keyword) of each step is matched to a code block, called a step definition.

INDEX

• Keywords
• Feature
• Descriptions
• Rule
• Example
• Steps
• Given
• When
• Then
• And/But
• *
• Background
• Scenario
• Examples
• Step arguments
• Doc strings
• Data tables

Keywords

Each line that isn’t a blank line has to start with a Gherkin keyword, followed by any text you like. The only exceptions are the feature and scenario descriptions.

The primary keywords are:

• Feature
• Rule
• Example (or Scenario)
• Given, When, Then, And, But for steps (or *)
• Background
• Scenario Outline (or Scenario Template)
• Examples (or Scenarios)

There are a few secondary keywords as well:

• """ (Doc Strings)
• | (Data Tables)
• @ (Tags)
• # (Comments)

Feature

The purpose of the Feature keyword is to provide a high-level description of a software feature, and to group related scenarios.

The first primary keyword in a Gherkin document must always be Feature, followed by a : and a short text that describes the feature.

You can add free-form text underneath Feature to add more description.

These description lines are ignored by Cucumber at runtime, but are available for reporting (They are included by default in html reports).

Feature: Guess the word

  The word guess game is a turn-based game for two players.
  The Maker makes a word for the Breaker to guess. The game
  is over when the Breaker guesses the Maker's word.

  Example: Maker starts a game

The name and the optional description have no special meaning to Cucumber. Their purpose is to provide a place for you to document important aspects of the feature, such as a brief explanation and a list of business rules (general acceptance criteria).

The free format description for Feature ends when you start a line with the keyword Background, Rule, Example or Scenario Outline (or their alias keywords).

You can place tags above Feature to group related features, independent of your file and directory structure.

Descriptions

Free-form descriptions (as described above for Feature) can also be placed underneath Example/Scenario, Background, Scenario Outline and Rule.

You can write anything you like, as long as no line starts with a keyword.

Rule

The (optional) Rule keyword has been part of Gherkin since v6.

The purpose of the Rule keyword is to represent one business rule that should be implemented. It provides additional information for a feature. A Rule is used to group together several scenarios that belong to this business rule. A Rule should contain one or more scenarios that illustrate the particular rule.

For example:

# -- FILE: features/gherkin.rule_example.feature
Feature: Highlander

  Rule: There can be only One

    Example: Only One -- More than one alive
      Given there are 3 ninjas
      And there are more than one ninja alive
      When 2 ninjas meet, they will fight
      Then one ninja dies (but not me)
      And there is one ninja less alive

    Example: Only One -- One alive
      Given there is only 1 ninja alive
      Then he (or she) will live forever ;-)

  Rule: There can be Two (in some cases)

    Example: Two -- Dead and Reborn as Phoenix
      ...

Example

This is a concrete example that illustrates a business rule. It consists of a list of steps.

The keyword Scenario is a synonym of the keyword Example.

You can have as many steps as you like, but we recommend 3-5 steps per example. Having too many steps will cause the example to lose its expressive power as a specification and documentation.

In addition to being a specification and documentation, an example is also a test. As a whole, your examples are an executable specification of the system.

Examples follow this same pattern:

1. Describe an initial context (Given steps)
2. Describe an event (When steps)
3. Describe an expected outcome (Then steps)

Steps

Each step starts with Given, When, Then, And, or But.

Cucumber executes each step in a scenario one at a time, in the sequence you’ve written them in. When Cucumber tries to execute a step, it looks for a matching step definition to execute.

Keywords are not taken into account when looking for a step definition. This means you cannot have a Given, When, Then, And or But step with the same text as another step.

Cucumber considers the following steps duplicates:

Given there is money in my account
Then there is money in my account

This might seem like a limitation, but it forces you to come up with a less ambiguous, more clear domain language:

Given my account has a balance of £430
Then my account should have a balance of £430

Given

Given steps are used to describe the initial context of the system - the scene of the scenario. It is typically something that happened in the past.

When Cucumber executes a Given step, it will configure the system to be in a well-defined state, such as creating and configuring objects or adding data to a test database.

The purpose of Given steps is to put the system in a known state before the user (or external system) starts interacting with the system (in the When steps). Avoid talking about user interaction in Given’s. If you were creating use cases, Given’s would be your preconditions.

It’s okay to have several Given steps (use And or But for number 2 and upwards to make it more readable).

Examples:

• Mickey and Minnie have started a game
• I am logged in
• Joe has a balance of £42

When

When steps are used to describe an event, or an action. This can be a person interacting with the system, or it can be an event triggered by another system.

It’s strongly recommended you only have a single When step per Scenario. If you feel compelled to add more, it’s usually a sign that you should split the scenario up into multiple scenarios.

Examples:

• Guess a word
• Invite a friend
• Withdraw money

Then

Then steps are used to describe an expected outcome, or result.

The step definition of a Then step should use an assertion to compare the actual outcome (what the system actually does) to the expected outcome (what the step says the system is supposed to do).

An outcome should be on an observable output. That is, something that comes out of the system (report, user interface, message), and not a behaviour deeply buried inside the system (like a record in a database).

Examples:

• See that the guessed word was wrong
• Receive an invitation
• Card should be swallowed

While it might be tempting to implement Then steps to look in the database - resist that temptation!

You should only verify an outcome that is observable for the user (or external system), and changes to a database are usually not.

And/But

If you have successive Given’s, When’s, or Then’s, you could write:

Example: Multiple Givens
  Given one thing
  Given another thing
  Given yet another thing
  When I open my eyes
  Then I should see something
  Then I shouldn't see something else

Or, you could make the example more fluidly structured by replacing the successive Given’s, When’s, or Then’s with And’s and But’s:

Example: Multiple Givens
  Given one thing
  And another thing
  And yet another thing
  When I open my eyes
  Then I should see something
  But I shouldn't see something else

Asterisk

Gherkin also supports using an asterisk (*) in place of any of the normal step keywords. This can be helpful when you have some steps that are effectively a list of things, so you can express it more like bullet points where otherwise the natural language of And etc might not read so elegantly.

For example:

Scenario: All done
  Given I am out shopping
  And I have eggs
  And I have milk
  And I have butter
  When I check my list
  Then I don't need anything

Could be expressed as:

Scenario: All done
  Given I am out shopping
  * I have eggs
  * I have milk
  * I have butter
  When I check my list
  Then I don't need anything

Background

Occasionally you’ll find yourself repeating the same Given steps in all of the scenarios in a Feature.

Since it is repeated in every scenario, this is an indication that those steps are not essential to describe the scenarios; they are incidental details. You can literally move such Given steps to the background, by grouping them under a Background section.

A Background allows you to add some context to the scenarios that follow it. It can contain one or more Given steps, which are run before each scenario, but after any Before hooks.

A Background is placed before the first Scenario/Example, at the same level of indentation.

For example:

Feature: Multiple site support
  Only blog owners can post to a blog, except administrators,
  who can post to all blogs.

  Background:
    Given a global administrator named "Greg"
    And a blog named "Greg's anti-tax rants"
    And a customer named "Dr. Bill"
    And a blog named "Expensive Therapy" owned by "Dr. Bill"

  Scenario: Dr. Bill posts to his own blog
    Given I am logged in as Dr. Bill
    When I try to post to "Expensive Therapy"
    Then I should see "Your article was published."

  Scenario: Dr. Bill tries to post to somebody else's blog, and fails
    Given I am logged in as Dr. Bill
    When I try to post to "Greg's anti-tax rants"
    Then I should see "Hey! That's not your blog!"

  Scenario: Greg posts to a client's blog
    Given I am logged in as Greg
    When I try to post to "Expensive Therapy"
    Then I should see "Your article was published."

Background is also supported at the Rule level, for example:

Feature: Overdue tasks
  Let users know when tasks are overdue, even when using other
  features of the app

  Rule: Users are notified about overdue tasks on first use of the day
    Background:
      Given I have overdue tasks

    Example: First use of the day
      Given I last used the app yesterday
      When I use the app
      Then I am notified about overdue tasks

    Example: Already used today
      Given I last used the app earlier today
      When I use the app
      Then I am not notified about overdue tasks
  ...

You can only have one set of Background steps per Feature or Rule. If you need different Background steps for different scenarios, consider breaking up your set of scenarios into more Rules or more Features.

For a less explicit alternative to Background, check out conditional hooks.

Tips for using Background

• Don’t use Background to set up complicated states, unless that state is actually something the client needs to know.
  For example, if the user and site names don’t matter to the client, use a higher-level step such as Given I am logged in as a site owner.
• Keep your Background section short.
  
  The client needs to actually remember this stuff when reading the scenarios. If the Background is more than 4 lines long, consider moving some of the irrelevant details into higher-level steps.
• Make your Background section vivid.
  Use colourful names, and try to tell a story. The human brain keeps track of stories much better than it keeps track of names like "User A", "User B", "Site 1", and so on.
• Keep your scenarios short, and don’t have too many.
  If the Background section has scrolled off the screen, the reader no longer has a full overview of what’s happening. Think about using higher-level steps, or splitting the *.feature file.

Scenario Outline

The Scenario Outline keyword can be used to run the same Scenario multiple times, with different combinations of values.

The keyword Scenario Template is a synonym of the keyword Scenario Outline.

Copying and pasting scenarios to use different values quickly becomes tedious and repetitive:

Scenario: eat 5 out of 12
  Given there are 12 cucumbers
  When I eat 5 cucumbers
  Then I should have 7 cucumbers

Scenario: eat 5 out of 20
  Given there are 20 cucumbers
  When I eat 5 cucumbers
  Then I should have 15 cucumbers

We can collapse these two similar scenarios into a Scenario Outline.

Scenario outlines allow us to more concisely express these scenarios through the use of a template with < >-delimited parameters:

Scenario Outline: eating
  Given there are  cucumbers
  When I eat  cucumbers
  Then I should have  cucumbers

  Examples:
    | start | eat | left |
    |    12 |   5 |    7 |
    |    20 |   5 |   15 |
</code>
</pre>

Examples

A Scenario Outline must contain an Examples (or Scenarios) section. Its steps are interpreted as a template which is never directly run. Instead, the Scenario Outline is run once for each row in the Examples section beneath it (not counting the first header row).

The steps can use <> delimited parameters that reference headers in the examples table. Cucumber will replace these parameters with values from the table before it tries to match the step against a step definition.

You can also use parameters in multiline step arguments.

Step Arguments

In some cases you might want to pass more data to a step than fits on a single line. For this purpose Gherkin has Doc Strings and Data Tables.

Doc Strings

Doc Strings are handy for passing a larger piece of text to a step definition.

The text should be offset by delimiters consisting of three double-quote marks on lines of their own:



Given a blog post named "Random" with Markdown body
  """
  Some Title, Eh?
  ===============
  Here is the first paragraph of my blog post. Lorem ipsum dolor sit amet,
  consectetur adipiscing elit.
  """



In your step definition, there’s no need to find this text and match it in your pattern. It will automatically be passed as the last argument in the step definition.

Indentation of the opening """ is unimportant, although common practice is two spaces in from the enclosing step. The indentation inside the triple quotes, however, is significant. Each line of the Doc String will be dedented according to the opening """. Indentation beyond the column of the opening """ will therefore be preserved.

Doc strings also support using three backticks as the delimiter:


Given a blog post named "Random" with Markdown body
  ```
  Some Title, Eh?
  ===============
  Here is the first paragraph of my blog post. Lorem ipsum dolor sit amet,
  consectetur adipiscing elit.
  ```
  


This might be familiar for those used to writing with Markdown.


Data Tables

Data Tables are handy for passing a list of values to a step definition:



Given the following users exist:
  | name   | email              | twitter         |
  | Aslak  | aslak@cucumber.io  | @aslak_hellesoy |
  | Julien | julien@cucumber.io | @jbpros         |
  | Matt   | matt@cucumber.io   | @mattwynne      |

  


Just like Doc Strings, Data Tables will be passed to the step definition as the last argument.