Agent skill
cucumber
Gherkin/Cucumber BDD specification language
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/cucumber
SKILL.md
Skill: cucumber
What I do
I provide Gherkin/Cucumber BDD expertise: feature files, scenario structure, step definitions, data tables, scenario outlines, and best practices for writing living documentation that drives tests.
When to use me
- Writing Gherkin feature files for BDD
- Designing scenarios that serve as living documentation
- Implementing step definitions in Go (godog), Ruby, or JavaScript
- Using data tables, scenario outlines, and backgrounds
- Bridging business language and automated tests
Core principles
- Business language first - Scenarios describe behaviour in domain terms, not UI steps
- Given-When-Then - Given (context), When (action), Then (outcome)
- One scenario, one behaviour - Each scenario tests exactly one rule
- Declarative over imperative - Say what, not how (avoid click/type steps)
- Living documentation - Features are specs that stakeholders can read
Patterns & examples
Feature file structure:
Feature: Order checkout
As a customer
I want to complete my purchase
So that I receive my items
Background:
Given I am a registered customer
And I have items in my cart
Scenario: Successful checkout with valid payment
Given my cart total is £25.00
When I complete checkout with valid payment
Then my order should be confirmed
And I should receive a confirmation email
Scenario: Checkout rejected with insufficient funds
Given my cart total is £25.00
When I complete checkout with insufficient funds
Then I should see a payment declined message
And my cart should remain unchanged
Scenario outlines (parameterised):
Scenario Outline: Shipping cost by region
Given my delivery address is in <region>
When I calculate shipping for <weight>kg
Then the shipping cost should be £<cost>
Examples:
| region | weight | cost |
| UK | 1 | 3.99 |
| UK | 5 | 7.99 |
| EU | 1 | 9.99 |
| US | 1 | 14.99 |
Step definitions (Go with godog):
func (s *OrderSteps) InitializeScenario(ctx *godog.ScenarioContext) {
ctx.Given(`^my cart total is £(\d+\.\d+)$`, s.cartTotalIs)
ctx.When(`^I complete checkout with valid payment$`, s.checkoutWithValidPayment)
ctx.Then(`^my order should be confirmed$`, s.orderConfirmed)
}
func (s *OrderSteps) cartTotalIs(total float64) error {
s.cart.SetTotal(total)
return nil
}
func (s *OrderSteps) checkoutWithValidPayment() error {
s.result = s.checkout.Process(s.cart, validPayment)
return nil
}
Data tables:
Scenario: Adding multiple items to cart
When I add the following items:
| name | quantity | price |
| Widget | 2 | 5.99 |
| Gadget | 1 | 12.50 |
Then my cart total should be £24.48
Anti-patterns to avoid
- ❌ Imperative steps (
When I click the submit button) — use declarative (When I submit my order) - ❌ UI-coupled steps (
Then I should see div.success) — use domain language - ❌ Long scenarios with 10+ steps (break into smaller focused scenarios)
- ❌ Scenario dependencies (each scenario must be independent)
- ❌ Incidental details (
Given a user "[email protected]" with password "abc123") — use roles/personas - ❌ NEVER use
env.GetEvents()or similar DB access in "Then" steps — useenv.GetView()and check for substring/footer - ❌ NEVER bypass UI with direct repo calls in "When" steps — call domain functions instead
- ❌ NEVER mix DB assertions with view assertions in same step file — migrate fully to one pattern
WRONG (DB-based Then step):
func thereShouldBeNEvents(ctx context.Context, n int) (context.Context, error) {
env := support.GetAppEnv(ctx)
count := len(env.GetEvents()) // ❌ DB access
if count != n { return ctx, fmt.Errorf("expected %d", n) }
return ctx, nil
}
CORRECT (View-based Then step):
func thereShouldBeNEvents(ctx context.Context, n int) (context.Context, error) {
env := support.GetAppEnv(ctx)
view := env.GetView() // ✅ View access
expectedFooter := fmt.Sprintf("Events: %d", n)
if !strings.Contains(view, expectedFooter) {
return ctx, fmt.Errorf("expected footer not found")
}
return ctx, nil
}
KB Reference
~/vaults/baphled/3. Resources/Knowledge Base/AI Development System/Skills/Testing-BDD/Cucumber.md
Related skills
bdd-workflow- Red-Green-Refactor cycle with Cucumbergodog- Go-specific Cucumber runnerginkgo-gomega- Alternative BDD framework for Goe2e-testing- End-to-end patterns that Cucumber drives
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