jest

What is jest?

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It works with projects using: Babel, TypeScript, Node, React, Angular, Vue, and more. It's designed to ensure correctness of any JavaScript codebase. It allows you to write tests with an approachable, familiar, and feature-rich API that gives you results quickly.

What are jest's main functionalities?

Unit Testing

Jest allows you to write unit tests for your JavaScript functions. In this example, a simple test is written to check if the addition of 1 and 2 equals 3.

test('adds 1 + 2 to equal 3', () => {
  expect(1 + 2).toBe(3);
});

Mocking

Jest provides a powerful mocking library that lets you mock objects, functions, and modules. In this example, an HTTP request is mocked to test the behavior of a function that fetches user data.

jest.mock('../api');

test('should fetch users', () => {
  const users = [{name: 'Bob'}];
  const resp = {data: users};
  axios.get.mockResolvedValue(resp);

  return Users.all().then(data => expect(data).toEqual(users));
});

Snapshot Testing

Snapshot testing enables you to test your UI or any serializable value to ensure it does not change unexpectedly. This example demonstrates testing an object against a snapshot, with some fields expected to match specific types rather than values.

test('will check the matchers and pass', () => {
  const user = {
    createdAt: new Date(),
    id: Math.floor(Math.random() * 20),
    name: 'LeBron James'
  };

  expect(user).toMatchSnapshot({
    createdAt: expect.any(Date),
    id: expect.any(Number)
  });
});

Asynchronous Testing

Jest supports testing of asynchronous code. In this example, an asynchronous function `fetchData` is tested to ensure it resolves with the expected value 'peanut butter'.

test('the data is peanut butter', async () => {
  await expect(fetchData()).resolves.toBe('peanut butter');
});

Other packages similar to jest

mocha

Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple. Mocha is often compared to Jest because of its flexible and configurable nature, but it requires more setup and configuration for features like mocking and snapshot testing, which Jest provides out of the box.

jasmine

Jasmine is a behavior-driven development framework for testing JavaScript code. It does not rely on browsers, DOM, or any JavaScript framework. Similar to Jest, it comes with an easy syntax that makes writing tests simple. However, Jest offers more modern features like snapshot testing and built-in support for test coverage.

ava

AVA is a test runner for Node.js with a concise API, detailed error output, and process isolation that lets you develop with confidence. AVA is designed to handle asynchronous testing more efficiently than Jest but lacks some of Jest's features like snapshot testing and built-in mocking.

chai

Chai is a BDD / TDD assertion library for node and the browser that can be delightfully paired with any JavaScript testing framework. It's often used alongside other testing frameworks like Mocha or Jest to provide more expressive assertions. Unlike Jest, Chai is purely an assertion library and does not provide test runners or mocking utilities.

README

Jest

JavaScriptational State Transfer for node.js with easy generating resource from Mongoose ORM

introduction

This module provides Resource base class with:

• Authentication
• Authorization
• Pagination
• Cache
• Throttling
• Validation
• MongooseResource
• Resources listing

synopsis

var express = require('express'),
    app = express(),
    Jest = require('jest'),
    mongoose = require('mongoose'),
    Schema = mongoose.Schema;

mongoose.connect('mongodb://localhost/app');

app.configure(function () {
    app.set('port', process.env.PORT || 80);
    app.use(express.logger('dev'));
    app.use(express.bodyParser());
    app.use(express.methodOverride());
    app.use(app.router);
});

// create mongoose model

var User = mongoose.model('user', new Schema({
    username: {type: String, required: true},
    email: String,
    password: {type: String, validate: [function(v) { return true}, 'custom validate']},
    credits: {type: Number, min: 1, max: 230},
    role: {type: String, 'default': 'user' ,enum: ['user', 'admin']},
    date: {type:Date, 'default': Date.now},
    groups: [{name:String, permissions: [{name:String, expires:Date}]}]
}));

// create mongoose resource for User model

var UserResource = Jest.MongooseResource.extend({
    init: function(){
        // call Jest.Resource constructor
        // passing the Model User we created
        this._super(User);

        // use array to decide which fields will be visible by API
        // this.fields = ['username','credits'];
        // use tree object to decide recursively which fields to expose
        this.fields = {username: true, credits: true, groups: {name: true, permissions: {name: true} }};

        // use list or
        this.update_fields = ['email', 'password'];

        // specify base query for the model
        this.default_query = function(query){
            return query.where('credits').gte(10);
        };

        // specify which fields can be used to filter
        this.filtering = {credits: true};

        // which http methods are allowed
        this.allowed_methods = ['get', 'post', 'put'];
    }
})

var api = new Jest.Api('api', app);

api.register('users', new UserResource());

app.listen(app.get('port'), function(){
    console.log('express started on port %d', app.get('port'));
})

now go to http://localhost/api/ to see the api's and http://localhost/api/users to work with User model the Jest way.

installation

$ npm install jest

documentation

There is none. But there is an example, and a test.

And maybe one day will be...