Cucumber-js is the JavaScript implementation of Cucumber, a popular Behavior-Driven Development (BDD) tool. It allows developers to write automated tests in plain language that can be understood by both technical and non-technical team members, bridging the gap between business requirements and software functionality.

Pros

• Encourages collaboration between developers, testers, and business stakeholders
• Supports writing tests in multiple languages using Gherkin syntax
• Integrates well with various JavaScript testing frameworks and tools
• Provides a clear and readable format for documenting software behavior

Cons

• Learning curve for teams new to BDD and Gherkin syntax
• Can lead to verbose test suites if not properly managed
• May require additional setup and configuration compared to traditional unit testing
• Performance can be slower compared to lower-level testing frameworks

Code Examples

1. Defining a simple step definition:

const { Given, When, Then } = require('@cucumber/cucumber');

Given('I have {int} cucumbers', function (count) {
  this.cucumberCount = count;
});

When('I eat {int} cucumbers', function (eaten) {
  this.cucumberCount -= eaten;
});

Then('I should have {int} cucumbers', function (expected) {
  assert.equal(this.cucumberCount, expected);
});

2. Using data tables in step definitions:

const { Given } = require('@cucumber/cucumber');

Given('the following users exist:', function (dataTable) {
  const users = dataTable.hashes();
  users.forEach(user => {
    // Add user to the system
    addUser(user.name, user.email);
  });
});

3. Implementing hooks:

const { Before, After } = require('@cucumber/cucumber');

Before(function () {
  // This hook runs before each scenario
  console.log('Starting scenario');
});

After(function () {
  // This hook runs after each scenario
  console.log('Scenario completed');
});

Getting Started

1. Install Cucumber-js:

   npm install @cucumber/cucumber
   

2. Create a feature file (e.g., features/example.feature):

   Feature: Example feature
     Scenario: Adding numbers
       Given I have entered 5 into the calculator
       And I have entered 7 into the calculator
       When I press add
       Then the result should be 12 on the screen
   

3. Implement step definitions (e.g., features/step_definitions/calculator_steps.js):

   const { Given, When, Then } = require('@cucumber/cucumber');
   const assert = require('assert');
   
   Given('I have entered {int} into the calculator', function (number) {
     this.numbers = this.numbers || [];
     this.numbers.push(number);
   });
   
   When('I press add', function () {
     this.result = this.numbers.reduce((a, b) => a + b, 0);
   });
   
   Then('the result should be {int} on the screen', function (expected) {
     assert.equal(this.result, expected);
   });
   

4. Run Cucumber-js:

   npx cucumber-js