jest-runner-cucumber

Jest Test Runner for the Cucumber Framework

npm i jest-runner-cucumber

Table of Contents

• Gherkin Features

• Cucumber Features

• Getting Started

  • Jest Config

    • moduleFileExtensions
    • runner
    • setupFiles (optional)
    • setupFilesAfterEnv
    • testMatch
    • restoreMocks (optional)

  • Cucumber

    • Feature
    • Hooks
    • Steps
    • World

  • Additional Features

    • Gherkin Variables
    • MockXHR

• Working Example

  • Jest Config

  • Features

    • Background
    • Scenario
    • Scenario Outline

  • Hooks

  • Steps

  • World

Gherkin Features

Supported	Feature	Notes
✅	And
✅	Background
✅	But
✅	Comments
✅	Data Table
✅	DocString	if it finds the docString is JSON, it will parse it for you
	Rule	haven't seen examples of this; not sure if it's worth it
✅	Scenario
✅	Scenario Outline

Cucumber Features

Supported	Feature	Notes
✅	After	called after each scenario in a feature file
✅	AfterAll	called after the feature file is completed; unlike Cucumber, you will have access to "this" context here.
	Attachments
✅	Before	called before each scenario per feature file
✅	BeforeAll	called before the feature file is started; unlike Cucumber, you will have access to "this" context here.
✅	Given
	setDefaultTimeout	use jest.setTimeout or set the timeout property in your jest config
✅	setDefinitionFunctionWrapper
✅	setWorldConstructor
	Tags	need to identify a way to pass tags through jest
✅	Then
✅	When

Additional Features

Supported	Feature	Notes
✅	gherkin variables used to populate feature files

Getting Started

Jest Config

If you have existing jest test cases that do not use Cucumber, you have two options:

1. create a separate configuration. You can use the Jest CLI to run against specific configurations: jest --config=path/to/your/config.json

2. add a "projects" array to your existing configuration; moving any existing test configuration to inside of the projects array. Then, add your new jest configuration:

    {
      "projects": [
        {
           "displayName": "Unit"
        },
        {
          "displayName": "Integration",
          "runner": "jest-runner-cucumber"
        }   
      ] 
    } 

moduleFileExtensions:

 "moduleFileExtensions": [
    "feature",
    "js",
    "jsx",
    "ts",
    "tsx"
 ]

* If you are not using typescript, remove "ts" and "tsx"

runner:

"runner": "jest-runner-cucumber"

setupFiles (optional):

 "setupFiles": [
    "<rootDir>/path/to/your/window-polyfill.ts"
 ]

* Add your polyfills here. Here's an example

setupFilesAfterEnv:

 "setupFilesAfterEnv": [
    "<rootDir>/path/to/your/world.ts",
    "<rootDir>/path/to/your/hooks.tsx",
    "<rootDir>/path/to/your/steps.ts"
 ]

testMatch:

 "testMatch": [
    "<rootDir>/path/to/your/features/*.feature"
 ]

transform:

"transform": {
    "^.+\\.(js|jsx|ts|tsx)$": "babel-jest"
}

* If you are not using typescript, remove "ts" and "tsx"

restoreMocks (optional):

"restoreMocks": true

If you are planning on writing integration tests, I highly recommend that you set this to true. There is an open bug for jest to fix an issue where it does not unset manual mocks that are defined using __mock__ folders. However, if this is set true, jest-runner-cucumber will perform a scan of all __mock__ folders and files and manually unmock them for you.

Cucumber

Feature

path/to/your/features/button.feature

Feature: Button
 
Given I go to home
When I click the login button
Then the login button is not visible

Hooks

path/to/your/hooks.tsx

import React from 'react';
import ReactDOM from 'react-dom';
import { act } from 'react-dom/test-utils'
import { AfterAll, BeforeAll } from 'cucumber';
 
import SignUp from './path/to/your/app';
 
BeforeAll(async function () {
    await act(async () => {
        ReactDOM.render(
            <SignUp/>,
            document.body
        )
    });
});
 
AfterAll(async function () {
    await act(async () => {
        ReactDOM.unmountComponentAtNode(
            document.body
        )
    });
});

You can choose to use the hooks to render/unmount your component before/after each feature file like above, or you can add a path to your application entry point to your jest configuration's setupFiles property. The latter is more performant.

Steps

path/to/your/steps.ts

import { Given, When, Then } from 'cucumber';
import { act } from 'react-dom/test-utils';
 
Given(/I go to (.*)$/, function(link) {
    window.location.hash = `#/${link}`;
});
 
When(/I click the (\S+) button$/, async function(name) {
    await act(async () => {
        document.querySelector(`[data-test-id="${name}"]`).click();
    });
});
 
Then(/the (\S+) button is (visible|not visible)$/, function(name, state) {
    expect(!!document.querySelector(`[data-test-id="${name}"]`))
        .toEqual(state === 'visible')
});

World

setWorldConstuctor allows you to set the context of "this" for your steps/hooks definitions. This can be helpful when you want to maintain state between steps/hooks or want your steps/hooks to have access to some predefined data. The values are accessible within all Hooks, and Steps by using this

path/to/your/world.ts

import { setWorldConstructor } from 'cucumber';
 
setWorldConstructor(
    class MyWorld {
        pages = [];
    }
);

Example Output

Below is an example output from running tests against the example

 PASS  test/features/scenarioOutline.feature (97 MB heap size)
  Feature: Sign Up - Submitting With Extra Emails
    ✓ Given the firstName text input value is Dayne (37 ms)
    ✓ And the lastName text input value is Mentier (11 ms)
    ✓ And the email text input value is [e-mail] (13 ms)
    ✓ And the password text input value is itsASecretShh... (9 ms)
    ✓ And the extraEmails checkbox input is not checked (2 ms)
    ✓ When the submit button is clicked (89 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body: (3 ms)
    ✓ And the successAlert is visible (2 ms)
    ✓ And the showExtraEmailsAlert is not visible (2 ms)
  Feature: Sign Up - Submitting Without Extra Emails
    ✓ Given the firstName text input value is Dayne (12 ms)
    ✓ And the lastName text input value is Mentier (11 ms)
    ✓ And the email text input value is [e-mail] (8 ms)
    ✓ And the password text input value is itsASecretShh... (10 ms)
    ✓ And the extraEmails checkbox input is checked (9 ms)
    ✓ When the submit button is clicked (45 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body: (1 ms)
    ✓ And the successAlert is visible (1 ms)
    ✓ And the showExtraEmailsAlert is visible (1 ms)
 
 PASS  test/features/scenario.feature (93 MB heap size)
  Feature: Sign Up - Without Extra Emails
    ✓ Given the firstName text input value is Dayne (11 ms)
    ✓ And the lastName text input value is Mentier (12 ms)
    ✓ And the email text input value is [e-mail] (11 ms)
    ✓ And the password text input value is itsASecretShh... (14 ms)
    ✓ When the submit button is clicked (66 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body: (5 ms)
    ✓ And the successAlert is visible (2 ms)
    ✓ And the showExtraEmailsAlert is not visible (2 ms)
  Feature: Sign Up - With Extra Emails
    ✓ Given the firstName text input value is Dayne (14 ms)
    ✓ And the lastName text input value is Mentier (12 ms)
    ✓ And the email text input value is [e-mail] (12 ms)
    ✓ And the password text input value is itsASecretShh... (9 ms)
    ✓ And the extraEmails checkbox input is checked (9 ms)
    ✓ When the submit button is clicked (49 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body: (1 ms)
    ✓ And the successAlert is visible (2 ms)
    ✓ And the showExtraEmailsAlert is visible (1 ms)
 
 PASS  test/features/scenarioBackground.feature (85 MB heap size)
  Feature: Sign Up - Without Extra Emails
    ✓ Given the firstName text input value is Dayne (14 ms)
    ✓ And the lastName text input value is Mentier (13 ms)
    ✓ And the email text input value is [e-mail] (15 ms)
    ✓ And the password text input value is itsASecretShh... (22 ms)
    ✓ When the submit button is clicked (66 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body: (3 ms)
    ✓ And the successAlert is visible (4 ms)
    ✓ And the showExtraEmailsAlert is not visible (2 ms)
  Feature: Sign Up - With Extra Emails
    ✓ Given the firstName text input value is Dayne (10 ms)
    ✓ And the lastName text input value is Mentier (8 ms)
    ✓ And the email text input value is [e-mail] (10 ms)
    ✓ And the password text input value is itsASecretShh... (8 ms)
    ✓ And the extraEmails checkbox input is checked (7 ms)
    ✓ When the submit button is clicked (46 ms)
    ✓ Then POST http://127.0.0.1:8080/api/sign-up is called with the request body:
    ✓ And the successAlert is visible (2 ms)
    ✓ And the showExtraEmailsAlert is visible (1 ms)
 
Test Suites: 3 passed, 3 total
Tests:       52 passed, 52 total
Snapshots:   0 total
Time:        7.603 s
Ran all test suites.

Gherkin Variables

This provides the ability to define variables in your feature files, and hold the values in a separate file. A few things to note for this functionality is:

1. the file must contain the same name as the feature file you're looking to populate
2. all variables start with a "$"; eg, in the feature file, the variable would be defined as $email, while the vars file would contain email
3. you can further split up your vars files by using the CUCUMBER_ENV variable. Using that, your files would look like this: featureFileName.CUCUMBER_ENV.vars.{js,ts,json}

For an example, see the example scenarioOutline feature file, and the accompanying variable file

MockXHR

One of the hardest thing I've found when using jest as a runner for integration tests is figuring out how to properly spy on api calls and mock the requests. I've included a helper class called MockXHR that simplifies the process. Below is an example of how to set it up in your World and Hooks

import React from 'react';
import ReactDOM from 'react-dom';
import { After, AfterAll, BeforeAll,setWorldConstructor } from 'cucumber';
import { MockXHR } from 'jest-runner-cucumber/dist/mocks/MockXHR';
 
import TestApp from 'my/root/path';
 
setWorldConstructor(
    class TestWorld {
        $mockXhr = new MockXHR([
            {
                url: '/api/sign-up',
                method: 'post',
                status: 200,
                response: {
                    message: 'thanks for signing up!'
                }
            },
            {
                url: '/api/sign-up',
                method: 'get',
                status: 200,
                response: {
                    registered: false
                }
            }
        ])
    }
)
 
After(function () {
    this.$mockServer.spy.mockClear();
});
 
AfterAll(async function () {
    ReactDOM.unmountComponentAtNode(document.body);
    this.$mockServer.destroy();
});
 
BeforeAll(async function () {
    ReactDOM.render(
        <TestApp/>,
        document.body
    );
});

MockXHR provides a spy that is called whenever a request goes out, this can be use your steps like this:

import { Then } from 'cucumber'
 
Then(/^(GET|PUT|POST|DELETE) (.*) is called with the (request body|params):$/,
    function (method, url, type, value) {
 
        const hasBody = type === 'request body';
 
        expect(this.$mockServer.spy).toHaveBeenCalledWith({
            ...hasBody ? {data: value} : {params: value},
            method,
            url 
        });
    }
);

Scenario: Without Extra Emails
  When the submit button is clicked
  Then POST /api/sign-up is called with the request body:
  """
   {
       "firstName": "Dayne",
       "lastName": "Mentier",
       "email": "[e-mail]",
       "password": "itsASecretShh...",
       "extraEmails": false
   }
  """

Internally, it uses xhr-mock. Unlike nock which causes memory leak issues because it is mutating native node modules, xhr-mock does not. I've also found that if your http lib is axios, you can also run into memory leak issues if you do not mock the follow-redirects. That lib has the same issue as nock; it mutates the native http and https modules, which causes leaking. If you are using axios make sure you add the following mock to one of your entry files:

jest.mock('follow-redirects', () => ({
    http: function () {
    },
    https: function () {
    }
}));