jest-cucumber/README.md

Execute Gherkin scenarios in Jest

# Jest Cucumber

Execute Gherkin scenarios in Jest

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<img src="./images/jest-cucumber-demo.gif?raw=true" alt="Cucumber Jest Demo" />

## Overview

jest-cucumber is an alternative to [Cucumber.js](https://github.com/cucumber/cucumber-js) that runs on top on [Jest](https://jestjs.io). 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 then allows you to link these Jest tests to your feature files and ensure that they always [stay in sync](https://github.com/bencompton/jest-cucumber/blob/master/docs/AdditionalConfiguration.md#disabling-scenario--step-definition-validation).

## 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](https://github.com/jest-community/vscode-jest) that allows you get realtime feedback as you're writing your tests and easily debug failing tests individually. [Cucumber](https://cucumber.io) is a popular tool for doing [Acceptance Test-Driven Development](https://en.wikipedia.org/wiki/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:

```
npm install jest-cucumber --save-dev
```

### Add a Feature file:

```gherkin
Feature: Logging in

Scenario: Entering a correct password
    Given I have previously created a password
    When I enter my password correctly
    Then I should be granted access
```

### Add the following to your Jest configuration:

```javascript
  "testMatch": [
    "**/*.steps.js"
  ],
```

### Add a step definition file that links to your feature file:

```javascript
// logging-in.steps.js

import { defineFeature, loadFeature } from 'jest-cucumber';

const feature = loadFeature('features/LoggingIn.feature');
```

### Add a Jest test for each scenario into your step definition file:

```javascript
// logging-in.steps.js

import { defineFeature, loadFeature } from 'jest-cucumber';

const feature = loadFeature('features/LoggingIn.feature');

defineFeature(feature, test => {
  test('Entering a correct password', ({ given, when, then }) => {

  });
});
```

### Add step definitions to your scenario Jest tests:

```javascript
// logging-in.steps.js

import { loadFeature, defineFeature } from 'jest-cucumber';
import { PasswordValidator } from 'src/password-validator';

const feature = loadFeature('specs/features/basic-scenarios.feature');

defineFeature(feature, (test) => {
  let passwordValidator = new PasswordValidator();
  let accessGranted = false;

  beforeEach(() => {
    passwordValidator = new PasswordValidator();
  });

  test('Entering a correct password', ({ given, when, then }) => {
    given('I have previously created a password', () => {
      passwordValidator.setPassword('1234');
    });

    when('I enter my password correctly', () => {
      accessGranted = passwordValidator.validatePassword('1234');
    });

    then('I should be granted access', () => {
      expect(accessGranted).toBe(true);
    });
  });
});
```

## Additional Documentation

* [Asynchronous steps](./docs/AsynchronousSteps.md)
* [Automatic step Binding](./docs/AutomaticStepBinding.md)
* [Backgrounds](./docs/Backgrounds.md)
* [Configuration options](./docs/AdditionalConfiguration.md)
* [Gherkin tables](./docs/GherkinTables.md)
* [Re-using step definitions](./docs/ReusingStepDefinitions.md)
* [Running the examples](./docs/RunningTheExamples.md)
* [Scenario outlines](./docs/ScenarioOutlines.md)
* [Step definition arguments](./docs/StepDefinitionArguments.md)
* [Using Docstrings](./docs/UsingDocstrings.md)