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Learning Behavior-driven development with Javascript
Learning Behavior-driven development with Javascript

Learning Behavior-driven development with Javascript: Create powerful yet simple-to-code BDD test suites in JavaScript using the most popular tools in the community

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Profile Icon Enrique Javier A Rubio
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Full star icon Full star icon Full star icon Full star icon Half star icon 4.9 (7 Ratings)
Paperback Feb 2015 392 pages 1st Edition
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zł177.99
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zł221.99
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Arrow left icon
Profile Icon Enrique Javier A Rubio
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Full star icon Full star icon Full star icon Full star icon Half star icon 4.9 (7 Ratings)
Paperback Feb 2015 392 pages 1st Edition
eBook
zł177.99
Paperback
zł221.99
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eBook
zł177.99
Paperback
zł221.99
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Learning Behavior-driven development with Javascript

Chapter 2. Automating Tests with Mocha, Chai, and Sinon

Before we start making some BDD, let's familiarize ourselves with the basic tools available in JavaScript to write and execute a test. In this chapter, we will explore the main capabilities of Mocha, the most popular test runner in JavaScript. We will perform the following tasks:

  • Writing expressive assertions using the Chai package
  • Creating test doubles using the Sinon and sinon-chai packages
  • Exploring the basic techniques for organizing our test codebase

To achieve these goals, we will perform a small code kata, or coding exercise, where we will be able to practice not only the tools, but also the test-first cycle explained in the previous chapter.

Node and NPM as development platforms

All the tools that we will use are written in JavaScript. A long time ago, the only way to execute JavaScript was to use a browser, but those days are long gone. Nowadays, we can execute our development tools from the command line during our normal development cycle or from a Continuous Integration (CI) server whenever we commit our changes to a source code repository.

The most easy and productive way to run our test tools is to use Node. Node is a lightweight and highly-scalable platform for JavaScript, written on top of the excellent V8 JavaScript virtual machine. Node is especially good for applications that perform high-volume IO, but it can also be used as a development platform, as we will see in a moment.

Installing Node and NPM

The examples in this book will work with Node Version 0.10.x or above. If you don't have it installed already, you must do so to follow the code examples.

Tip

It is recommended that you do not install a version of Node...

Configuring your project with NPM

With the installation of Node, the Node Package Manager (NPM) is also installed. NPM is actually the utility that we will use for our normal development cycle.

NPM allows you to install libraries, manage the dependencies of your projects, and define a set of commands to build your code.

To start, just create a new folder for your project and initialize it from there:

$ me@~> mkdir validator
$ me@~> cd validator
$ me@~/validator> npm init

The last command, npm init, will invoke NPM to generate package.json inside the current directory; during the process, it will ask you some questions. Most of them are self-explanatory, but if you do not know what to answer just press ENTER. Do not worry; you will be able to edit the package.json file later. This is my package.json file:

{
  "name": "validator",
  "version": "0.1.0",
  "description": "A validation service for Weird LTD.",
  "main&quot...

Introducing Mocha

Mocha is a modern test runner that can be executed from Node as well as inside a browser. As we saw earlier, our main approach is to use Node. In this book, I am using Mocha Version 1.20.1, but any 1.x version should be OK.

We have already installed Mocha using NPM, so we can run it with the following command:

$ me@~/validator> ./node_modules/.bin/mocha -u bdd -R spec -t 500 --recursive

It fails because we do not have any test yet; we will fix it later. I will explain the exact meaning of these parameters in a moment. For now, note that, to execute Mocha, we need to find out where NPM has installed the executable of the tool. A package can be a simple library, or it can also contain an executable command-line tool, as is the case with Mocha. NPM always will install this executable in the node_modules/.bin/ folder; hence, we need to execute ./node_modules/.bin/mocha in order to invoke Mocha.

This would not have been necessary if we had installed Mocha as a global package...

More expressive assertions with Chai

We have already installed chai as a dependency of our project, but we have not yet used it. Specifically, I am using version 1.9.1, but any 1.x version should be OK.

Until now, we have been using the standard assert package to create our assertions. The assert package is not bad, but it is limited to a few assertions. It is not extensible, and some people found it a bit difficult to read. I personally always find myself wondering, "Is the first parameter the actual value or the expected one?" Actually, the first parameter is the actual value, and the second one is the expected value. This is important because the report message depends on distinguishing the actual value from the expected one. Let's change the code of our test to use chai:

var chai = require('chai'),
    expect = chai.expect,
    validator = require('../lib/validator');

describe('A Validator', function() {
  it('will return error.nonpositive...

Red/Green/Refactor

Now that we have a basic knowledge of Chai, we can continue with our coding. The code we already have in place is clearly not correct, so we need to add another test that forces us to make the code right.

Currently, we are implementing the rule about errors for nonpositive numbers, so we should finish it before continuing. Which test could we add to make our implementation fail? We can try testing the validator with valid numbers. Let's see the result:

describe('A Validator', function() {
  it('will return no errors for valid numbers', function() {
    expect(validator(3)).to.be.empty;
  });

  it('will return error.nonpositive for not strictly positive numbers', function() {
    expect(validator(0)).to.be.deep.equal(['error.nonpositive']);
  });
});

Note that we have added a new test for valid numbers that is failing. So now we fix it in a very simple way in lib/validator.js:

module.exports = function (n) {
  if(n === 0)
    return...

Test doubles with Sinon

A few weeks after going to production, our validator is a complete success but it also happens that potential new customers would like to have different sets of validation rules. Fortunately, our validator is configurable, but we somehow need to specify a different configuration for each customer.

The act of configuring a different set of rules for each customer is clearly another operation of the system and, hence, a different feature, so we are not really interested in testing it in the validator tests. We would like to isolate the tests about the validator feature and the configuration feature. To do so, we need to create an interface in a way that allows the validator to ask for the correct set of rules for the configuration. Then we can create a test double for such an interface in our tests. The test double will impersonate the real configuration and allow us to isolate our tests.

When creating these test doubles we need to design the shape of the interfaces...

Node and NPM as development platforms


All the tools that we will use are written in JavaScript. A long time ago, the only way to execute JavaScript was to use a browser, but those days are long gone. Nowadays, we can execute our development tools from the command line during our normal development cycle or from a Continuous Integration (CI) server whenever we commit our changes to a source code repository.

The most easy and productive way to run our test tools is to use Node. Node is a lightweight and highly-scalable platform for JavaScript, written on top of the excellent V8 JavaScript virtual machine. Node is especially good for applications that perform high-volume IO, but it can also be used as a development platform, as we will see in a moment.

Installing Node and NPM

The examples in this book will work with Node Version 0.10.x or above. If you don't have it installed already, you must do so to follow the code examples.

Tip

It is recommended that you do not install a version of Node whose...

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Description

This book is ideal for any JavaScript developer who is interested in producing well-tested code. If you have no prior experience with testing, Node.js, or any other tool, do not worry, as they will be explained from scratch.

Who is this book for?

TThis book is ideal for any JavaScript developer who is interested in producing well-tested code. If you have no prior experience with testing, Node.js, or any other tool, do not worry, as they will be explained from scratch.

What you will learn

  • Understand the basic concepts of BDD and how it is different from classic unit testing
  • Divide your system into different modules that can be tested separately, but at the same time not falling into the trap of unit testing
  • Use Mocha, Sinon.JS, and Chai to write expressive BDD features
  • Implement Cucumber.js to automate tests written in Gherkin so that your stakeholders can understand them
  • Discover how to test asynchronous systems, either based on callbacks or promises
  • Test a RESTful web API and a rich UI using WebDriverJS and Protractor
  • Refactor and keep your test code base maintainable using best practices and patterns such as PageObject

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Publication date : Feb 19, 2015
Length: 392 pages
Edition : 1st
Language : English
ISBN-13 : 9781784392642
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Length: 392 pages
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ISBN-13 : 9781784392642
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Tools :

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Table of Contents

11 Chapters
1. Welcome to BDD Chevron down icon Chevron up icon
2. Automating Tests with Mocha, Chai, and Sinon Chevron down icon Chevron up icon
3. Writing BDD Features Chevron down icon Chevron up icon
4. Cucumber.js and Gherkin Chevron down icon Chevron up icon
5. Testing a REST Web API Chevron down icon Chevron up icon
6. Testing a UI Using WebDriverJS Chevron down icon Chevron up icon
7. The Page Object Pattern Chevron down icon Chevron up icon
8. Testing in Several Browsers with Protractor and WebDriver Chevron down icon Chevron up icon
9. Testing Against External Systems Chevron down icon Chevron up icon
10. Final Thoughts Chevron down icon Chevron up icon
Index Chevron down icon Chevron up icon

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Mike Ludemann Jul 18, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Alle wichtigen Information und mehr sind vorhanden.
Amazon Verified review Amazon
SoftMil Jakub Milkiewicz PL7851665795 May 22, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I am a pretty experienced developer (8-9 years mostly Java and other JVM-languages) who thought was pretty familiar with TDD, BDD and code design concepts. Unfortunately i was totally wrong ! The book really allowed me to open my eyes and see how much i was missing in these topics. It allowed me to finally understand the blurry line between TDD and BDD, write better tests, design in a more loose-coupled way and finally run-away from unit-tests (class/method-level unit tests) obsession and focus on features-testing as the right level of granularity for tests. The book (i haven't reached the last page yet) really reminds me Growing Object-Oriented Software, Guided by Tests book but i find it way more easy to read (written by non-native speaker), with complex concepts expressed clearly (always with an example ! ) and with a slightly different test-scope: building "logic/business" layer using BDD (my 2 favorite chapters), then REST API (with business layer being test double/stubbed) and finally UI all developed using test-first approach. That kind of approach seems to match with "Integration Tests Are a Scam" by J.B. Rainsberger.Although I am not js programmer and all examples and tools used in the book are javascript based, I didn't have any problem to read/use them (the author even drives you on installing all tools and shares his best practices on using them) so the book is a really good choice for non-javascript developers who would like to make a deep dive into modern way of building software using tests.I only wish the book was not a softcover...
Amazon Verified review Amazon
souidi sofian Jul 12, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book is very well done. He first explains what a test can be the difference in bdd and tdd. It teaches us to structure our tests with a practical case. You learn to test multiple browser using Protractor and WebDriver and even a rest web api. This book is to read for those who want to master the tests.
Amazon Verified review Amazon
Juanfe Mar 26, 2016
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Enrique Amodeo has been so far one of the best tech writers I have found. Neither BDD or TDD was familiar to me, yet in the first chapters of the book I started to understand a lot, even to the point of being myself able to explain to others who also want to learn BDD and have some experience with TDD.This book is a must have if you want to become a better javascript developer. So far my experience has been great, but this doesn't mean that I haven't had my challenges. This is not easy, so keep the good spirits up and trust Amodeo, he is simply the best.
Amazon Verified review Amazon
M. Chowdhury Jul 13, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Pretty comprehensive coverage on BDD. I have limited experience in JavaScript, and but it's not difficult to follow at all. The startup example was interesting for me to follow the BDD concepts. Chapters four, five and six on CucumberJS, REST API testing and WebDriverJS were the best for me. Highly recommend to any one interested in BDD in JS or other languages.
Amazon Verified review Amazon
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