Jest-cucumber-extra NPM

Jest Cucumber Extra

Execute Gherkin scenarios in Jest with extra functionality

Overview

jest-cucumber-extra is an alternative to Cucumber.js that is forked from jest-cucumber and runs on top on Jest. Instead of using describe and it blocks, you instead write a Jest test for each scenario, and then define Given, When, and Then step definitions inside of your Jest tests. jest-cucumber-extra then allows you to link these Jest tests to your feature files and ensure that they always stay in sync.

Motivation

Jest is an excellent test runner with great features like parallel test execution, mocking, snapshots, code coverage, etc. If you're using VS Code, there's also a terrific Jest extension that allows you get realtime feedback as you're writing your tests and easily debug failing tests individually. Cucumber is a popular tool for doing Acceptance Test-Driven Development and creating business-readable executable specifications. This library aims to achieve the best of both worlds, and even run your unit tests and acceptance tests in the same test runner.

Getting Started

Install Jest Cucumber Extra:

npm install jest-cucumber-extra --save-dev

Add a Feature file:

Feature: Earth shape

  Background:
    Given properties:
      | earthShape   | unknown |
      | realityState | real    |
      And property "galaxy" is "Milky Way"

  Scenario: Round earth
    Given I am normal
    When I talk
    Then result "earthShape" should be "round"

Add unit tests that link to your feature file:

import { defineFeature, DefineStepFunction, World, loadFeature, CommonSteps } from '../src';

// Define the feature loaded from feature file
defineFeature(
  loadFeature('./basic-scenarios.feature', {
    tagFilter: 'not @excluded',
  }),
  (test) => {
    // Create "background" steps
    const background = (given: DefineStepFunction) => {
      // Utilize "common" steps for repeatable steps
      CommonSteps.givenProperties(given);
      CommonSteps.givenPropertyString(given);
    };

    // Create test block for each scenario
    test('Round earth', ({ given, when, then }) => {
      // Create steps that match the feature file
      background(given);

      given('I am normal', (world: World) => {
        // Utilize the world object to reference
        // data from step to step
        world.setGivenProp('earthShape', 'round');
      });

      when('I talk', (world: World) => {
        world.setResultProp('earthShape', world.getGiven().earthShape);
      });

      CommonSteps.thenResultPropertyStringShouldBe(then);
    });