cucumber-best-practices（黄瓜最佳实践）

Cucumber Best Practices

Master patterns and practices for effective Cucumber testing.

Scenario Design Principles

1. Write Declarative Scenarios

Focus on what needs to happen, not how it happens.

❌ Imperative (implementation-focused):

Scenario: Add product to cart
  Given I navigate to "http://shop.com/products"
  When I find the element with CSS ".product[data-id='123']"
  And I click the button with class "add-to-cart"
  And I wait for the AJAX request to complete
  Then the element ".cart-count" should contain "1"

✅ Declarative (business-focused):

Scenario: Add product to cart
  Given I am browsing products
  When I add "Wireless Headphones" to my cart
  Then my cart should contain 1 item

2. One Scenario, One Behavior

Each scenario should test exactly one business rule or behavior.

❌ Multiple behaviors in one scenario:

Scenario: User registration and login and profile update
  Given I register a new account
  When I log in
  And I update my profile
  And I change my password
  Then everything should work

✅ Separate scenarios:

Scenario: Register new account
  When I register with valid details
  Then I should receive a confirmation email

Scenario: Login with new account
  Given I have registered an account
  When I log in with my credentials
  Then I should see my dashboard

Scenario: Update profile
  Given I am logged in
  When I update my profile information
  Then my changes should be saved

3. Keep Scenarios Independent

Each scenario should set up its own preconditions.

❌ Dependent scenarios:

Scenario: Create order
  When I create order #12345

Scenario: View order
  When I view order #12345  # Depends on previous scenario!

✅ Independent scenarios:

Scenario: View order
  Given an order exists with ID "12345"
  When I view the order details
  Then I should see the order information

4. Use Background Wisely

Use Background for common setup, but don't overuse it.

✅ Good use of Background:

Feature: Shopping Cart

  Background:
    Given I am logged in as a customer

  Scenario: Add product to cart
    When I add a product to my cart
    Then my cart should contain 1 item

  Scenario: Remove product from cart
    Given I have a product in my cart
    When I remove the product
    Then my cart should be empty

❌ Background doing too much:

Background:
  Given I am on the homepage
  And I click the menu
  And I navigate to products
  And I filter by category "Electronics"
  And I sort by price
  # Too much setup! Not all scenarios need all of this

Feature Organization

Group Related Scenarios

Feature: User Authentication

  Scenario: Successful login
    ...

  Scenario: Failed login with wrong password
    ...

  Scenario: Account lockout after multiple failures
    ...

Use Tags Effectively

@smoke @critical
Scenario: Login with valid credentials
  ...

@slow @integration
Scenario: Password reset email workflow
  ...

@wip
Scenario: OAuth login
  # Work in progress
  ...

Run specific tags:

# Run smoke tests
cucumber --tags "@smoke"

# Run all except WIP
cucumber --tags "not @wip"

# Run smoke AND critical
cucumber --tags "@smoke and @critical"

# Run smoke OR critical
cucumber --tags "@smoke or @critical"

Writing Good Gherkin

Use Domain Language

Write in the language of the business domain, not technical terms.

❌ Technical language:

Scenario: POST request to /api/users
  When I send a POST to "/api/users" with JSON payload
  And the response status is 201

✅ Domain language:

Scenario: Register new user
  When I register a new user account
  Then the user should be created successfully

Keep Steps at the Same Level

Don't mix high-level and low-level details.

❌ Mixed levels:

Scenario: Purchase product
  Given I am logged in
  When I add a product to cart
  And I click the element with ID "checkout-btn"  # Too detailed!
  And I enter credit card "4111111111111111"      # Too detailed!
  Then I complete the purchase

✅ Consistent level:

Scenario: Purchase product
  Given I am logged in
  And I have a product in my cart
  When I checkout with a credit card
  Then my order should be completed
  And I should receive a confirmation email

Avoid Conjunctive Steps

Don't use "And" to combine multiple distinct actions in prose.

❌ Conjunctive step:

When I log in and add a product to cart and checkout

✅ Separate steps:

When I log in
And I add a product to my cart
And I proceed to checkout

Scenario Outlines

Use for True Variations

Use Scenario Outlines when you need to test the same behavior with different data.

✅ Good use:

Scenario Outline: Login validation
  When I log in with "<username>" and "<password>"
  Then I should see "<message>"

  Examples:
    | username | password | message                |
    | valid    | valid    | Welcome                |
    | invalid  | valid    | Invalid username       |
    | valid    | invalid  | Invalid password       |
    | empty    | empty    | Username required      |

❌ Overusing Scenario Outline:

# Don't use Scenario Outline for unrelated test cases
Scenario Outline: Multiple features
  When I use feature "<feature>"
  Then result is "<result>"

  Examples:
    | feature        | result    |
    | login          | success   |
    | registration   | success   |
    | cart           | empty     |  # These are different behaviors!

Keep Examples Meaningful

Scenario Outline: Discount calculation
  Given a customer with "<membership>" status
  When they purchase items totaling $<amount>
  Then they should receive a $<discount> discount

  Examples: Standard discounts
    | membership | amount | discount |
    | silver     | 100    | 5        |
    | gold       | 100    | 10       |
    | platinum   | 100    | 15       |

  Examples: Minimum purchase thresholds
    | membership | amount | discount |
    | silver     | 49     | 0        |
    | silver     | 50     | 2.50     |

Step Definition Patterns

Create Reusable Steps

// Generic, reusable
When('I fill in {string} with {string}', async function(field, value) {
  await this.page.fill(`[name="${field}"]`, value);
});

// Used in multiple scenarios:
When('I fill in "email" with "test@example.com"')
When('I fill in "password" with "secure123"')
When('I fill in "search" with "products"')

Avoid Over-Generic Steps

Balance reusability with readability.

❌ Too generic:

When('I do {string} with {string} and {string}', ...)

✅ Specific and readable:

When('I log in with {string} and {string}', ...)
When('I search for {string} in {string}', ...)

Data Management

Use Factories for Test Data

// support/factories.js
const faker = require('faker');

class UserFactory {
  static create(overrides = {}) {
    return {
      firstName: faker.name.firstName(),
      lastName: faker.name.lastName(),
      email: faker.internet.email(),
      password: 'Test123!',
      ...overrides
    };
  }
}

// Use in steps
Given('I register a new user', async function() {
  const user = UserFactory.create();
  this.currentUser = user;
  await this.api.register(user);
});

Avoid Hardcoded IDs

❌ Hardcoded:

Given user "12345" exists
When I view order "67890"

✅ Named entities:

Given a user "john@example.com" exists
When I view my most recent order

Error Handling

Test Happy and Unhappy Paths

@happy-path
Scenario: Successful checkout
  Given I have items in my cart
  When I complete the checkout process
  Then my order should be confirmed

@error-handling
Scenario: Checkout with expired card
  Given I have items in my cart
  When I checkout with an expired credit card
  Then I should see an error message
  And my order should not be processed

@edge-case
Scenario: Checkout with insufficient inventory
  Given I have a product in my cart
  But the product is out of stock
  When I attempt to checkout
  Then I should be notified about stock unavailability

Performance

Tag Slow Tests

@slow @integration
Scenario: Full order workflow with email notifications
  # Takes 30 seconds to run
  ...

Parallel Execution

Ensure scenarios can run in parallel:

// cucumber.js
module.exports = {
  default: '--parallel 4'
};

Maintenance

Regular Review

• Remove obsolete scenarios
• Update scenarios when requirements change
• Refactor duplicate steps
• Keep features organized

Version Control

features/
  authentication/
    login.feature
    registration.feature
  shopping/
    cart.feature
    checkout.feature
  admin/
    user-management.feature

Common Anti-Patterns

❌ Testing implementation details:

Then the database should have 1 record in the users table

❌ UI-specific assertions in business scenarios:

Then I should see a red error message in the top right corner

❌ Using Given for actions:

Given I click the submit button  # This is a When, not a Given!

❌ Technical jargon:

When I POST to /api/v1/users with JSON body

Testing Pyramid

Use Cucumber appropriately in your test strategy:

• E2E Cucumber Tests: Critical user journeys (20%)
• Integration Tests: API/service interactions (30%)
• Unit Tests: Business logic (50%)

Don't try to test everything with Cucumber. Use it for high-value acceptance tests.

Remember: Cucumber tests should document behavior, facilitate collaboration, and provide confidence that the system works as expected from a business perspective.