Cucumber & Gherkin Skill

Cucumber & Gherkin

BDD testing framework with plain-text executable specifications and Ruby step definitions.

Feature file (.feature) ──> Step Definitions (Ruby) ──> System under test

Gherkin Quick Reference

Feature: Short description
  Optional multi-line description.

  Background:
    Given common setup for all scenarios

  Rule: Business rule grouping (Gherkin 6+)

    Scenario: Concrete example
      Given an initial context
      When an action occurs
      Then expected outcome
      And additional assertion
      But negative assertion

    Scenario Outline: Parameterized
      Given there are <start> items
      When I remove <remove> items
      Then I should have <remaining> items

      Examples:
        | start | remove | remaining |
        |    12 |      5 |         7 |
        |    20 |      5 |        15 |

Step keywords: Given (setup), When (action), Then (assertion), And/But (continuation), * (bullet)

Data tables:

Given the following users exist:
  | name  | email             | role  |
  | Alice | alice@example.com | admin |

Doc strings:

Given a blog post with content:
  """markdown
  # My Post Title
  Content here.
  """

Tags: @smoke @critical on Feature/Rule/Scenario/Examples. Expressions: @smoke and not @slow, (@smoke or @critical) and not @wip

Ruby Step Definitions

# Cucumber Expressions (preferred)
Given('I have {int} cucumbers in my belly') do |count|
  @belly = Belly.new
  @belly.eat(count)
end

When('I wait {int} hour(s)') do |hours|
  @belly.wait(hours)
end

Then('my belly should growl') do
  expect(@belly.growling?).to be true
end

# Data table
Given('the following users exist:') do |table|
  table.hashes.each { |row| User.create!(row) }
end

# Doc string
Given('a JSON payload:') do |json|
  @payload = JSON.parse(json)
end

Cucumber Expressions: {int}, {float}, {word}, {string}, {} (anonymous). Optional: cucumber(s). Alternatives: color/colour.

State sharing: Use instance variables (@user) or World modules:

module MyWorld
  def current_user
    @current_user ||= create(:user)
  end
end
World(MyWorld)

Hooks

Before do |scenario|
  @browser = Browser.new
end

After do |scenario|
  save_screenshot("failure.png") if scenario.failed?
end

Before('@database') do
  DatabaseCleaner.start
end

After('@database') do
  DatabaseCleaner.clean
end

BeforeAll do
  # once before any scenario
end

AfterAll do
  # once after all scenarios
end

Order: BeforeAll > (Before > Background > Steps > After) per scenario > AfterAll

Running

bundle exec cucumber
cucumber --tags "@smoke and not @wip"
cucumber features/login.feature:10
cucumber --dry-run
cucumber --format html --out report.html
bundle exec parallel_cucumber features/

Best Practices

Declarative over imperative:

# Good                          # Avoid
When "Bob" logs in              When I visit "/login"
Then he sees his dashboard      And I enter "bob" in "username"
                                And I click "Login"

Describe what the system does, not how
One behavior per scenario, 3-5 steps
Keep Background short (≤4 lines), essential context only
Use domain language stakeholders understand

References

For comprehensive details:

references/gherkin-syntax.md — Complete Gherkin language reference (keywords, data tables, tags, i18n)
references/step-definitions.md — Ruby step definition patterns (data tables, doc strings, custom parameter types, World context, organization)
references/hooks-config.md — Hooks, cucumber.yml configuration, reporters, Capybara integration
references/best-practices.md — Anti-patterns, naming conventions, collaboration patterns, refactoring

Agent Skills: Cucumber & Gherkin

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