Unit testing is a software testing method where individual pieces of code (usually the smallest piece of code that can be logically isolated in a system) are tested in isolation. To replace console.log() with a function where you provide the implementation, you would use a stub or a mock. A stub is a type of spy, but whereas a stub replaces a real function with your function, a spy does not. Jest is another popular testing framework for Node. This comes with an inherent understanding of what you’re trying to test for and how the code should function. It helps improve the quality of your code and reduces the amount of time and money you spend on bug fixing. For Node.js, the framework available for Testing is called Jasmine. From that point forward, it should run predictably. 1660. As you probably know, Date.now() returns the number of milliseconds since the Unix Epoch, and so is always changing. Published Nov 16, 2015Last updated Jun 11, 2017. In this article, we focused on four of the most popular frameworks. Creating a mock is super easy using Sinon: Remember that one of the things a test framework does is to define a test lifecycle. A Sinon spy that spies on console.log(). Does it work the same? It is very extensible and has a lot of plugins, extensions, and libraries designed to run on top of it. What you’ll learn. Running a linter on your code is called linting, a technique that can be very handy for discovering issues like: You might remember from Unit 7 that the npm registry contains many, many tools for linting. npm also saves both eslint and eslint-config-google to the devDependencies section of your package.json, which now should look like this: There are a number of ways to configure ESLint, but I recommend using package.json in order to minimize the number of metadata files you have to drag around in your projects. According to “The State of JavaScript 2019,” the most popular JavaScript testing frameworks and libraries are: In this guide, we’ll compare four of the most popular and widely used frameworks from the chart above: Jest, Jasmine, AVA, and Mocha. Node.js Unit Testing In-Depth A focused, in-depth look into Node.js unit testing, from absolute beginner to very advanced. Why unit testing NodeJs apps? This installs the latest version of the Istanbul command-line interface (called nyc) and saves nyc to the devDependencies section of your package.json. Snapshots. You’re likely to run across it, so let’s take a look here. I then showed you how to: The unit concludes with a solo exercise, which is to finish writing the tests and implementation code found in the skeleton logger files. Don’t get down on yourself if you see lots of errors at first. We will go through everything from the simplest JavaScript function to ES6 classes & private code testing. https://logrocket.com/signup/. A mock function is a test double that replaces a real function with a set of expectations. Notice the console.log output shows up in the test report. In this example, I’ve used Node’s assert module, which is not the most expressive assertion library. Before you actually write code, I suggest reading through the entire section. Making sure your Node instance continues to serve resources to your app is where things get tougher. Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser. The repo for the code lab session of JSLovers meet-up on 17th March 2019! By J Steven Perry Published January 16, 2019. Testing – Unit 9; Part Two: Apply what you’ve learned: Node.js in Practice – Units 10-14. What you'll learn. Basic knowledge of node is required. B: The pretest script runs before the test script when you run npm test. Source code for the learning path. We can then verify that it has been invoked the expected number of times. The upcoming exercise uses the following directory layout: Bottom line: If your company has a standard, follow it. D. It automatically runs a code coverage tool that you plug into its configuration. This is because when the test fails, the focus will be on the latest changes made, Refactoring code is made easier since changes can be verified using tests to ensure that the unit being tested still behaves in the desired manner, Costs that would be incurred fixing bugs or due to system outages occasioned by bugs are reduced, Describing the format used to convey test expectations, Creating a way of accessing the application or code to be tested, Ease of setup — Getting up and running with your tests should take a minimal amount of effort, Well supported — There is plenty of excellent documentation and communities to get help, A wide array of feature sets — The framework has things such as matchers, spies, mocking in-built, Speed — For tests that are CPU-bound, choosing the right framework can save you a lot of time during test runs, Ease of reporting — Coverage reports should be easy to generate using built-in reporting and external reporting libraries should be easy to integrate, Ease of integration — A good testing library should be easy to integrate into your continuous integration process, Easy set-up with flexible and easy configuration and less boilerplate code than other frameworks, Optimal performance — tests are parallelized by running them in their own processes to maximize performance, Useful features such as snapshots, coverage, and test watching, Displays multiple error messages for the same error. To get started, create a simple Node.js application by creating an empty folder and running npm init. It can require more dependencies during initial setup (e.g., Simple to set up — Jasmine has a CLI tool that creates a spec folder and a JSON configuration file, so with one command you’re ready to start testing your code, Thoroughly tested, documented, and supported by numerous, Behavior-driven development focused with descriptive syntax, Supported by many CI servers with plugins available for those that don’t have out-of-the box support. The test code needs to be written in a separate file, and the word 'spec' should be appended to the file name. Let’s modify the test suite in Listing 1 to use Chai. Minimalism is the focus of AVA. Mocha is a feature-rich JavaScript test framework running on Node.js and in the browser, making asynchronous testing simple and fun. To start, paste the following snippet into your package.json just after the devDependencies section. With your project under version control, you can use Buddy to streamline the testing process down to a single push to the repository: Create a free account with Buddy; Select the Git provider with your Node.js project; Create a new pipeline and set it to automatic mode (on push) Add Node.js action (npm install and npm test are already entered) Run your test cases against the code under test until all the test cases pass. Next, we will install the following packages for our application and testing environment. D: While you can use a code coverage tool with a test framework, you do this outside the test framework. Mocha is the core framework, that you can define test cases and has its own cute reporting. We’ll revisit mocks and stubs later in this unit. A Mocha test suite using Chai’s BDD-style assertion library. Unlike a stub, a mock does not provide an implementation. I’ve also left a few reference blocks of code to assist you. Test doubles are useful when it’s inconvenient, or even impossible, to run test cases against production code. The example in Listing 2 may not look much different from the first test suite, but using Chai’s BDD-style assertion syntax makes the test more readable. Unit Testing in Node.js. Mocha, like Jasmine, has been around for quite a while. This is because the real console.log() was replaced with the stub. The more code you exercise, the more bugs you uncover. Spies, stubs and mocks - … We’ll use ES6 syntax (parserOptions). It was last updated on March 10, 2020. Later in this unit, I show you how to configure and run the linter as two separate npm scripts in your npm test lifecycle. JavaScript and Node.js have so many testing and assertion libraries like Jest, Jasmine, Qunit, and Mocha. The community is still growing and there isn’t a lot of documentation or tutorials like other testing frameworks, Highly extensible with support for various assertion and mocking libraries, Adding support for generators to test suites is relatively easy. LogRocket is like a DVR for web apps, recording literally everything that happens on your site. Istanbul is a popular library for testing code coverage in JavaScript, and there is a Node module for it. Create a file index.jsto write our application: Assuming you are fairly familiar with Express, the above code should be easy to follow. If you’re reading this blog, you’re probably already familiar with Node.js. On my computer the full path is ~/src/projects/IBM-Developer/Node.js/Course/Unit-9. From the terminal window, enter this command: npm i --save-dev sinon. There are TODO: comments in the skeletons where you will need to write code. This is done by using the Node package manager. The repository contains both the tests using Mocha 1 and Jest, however I prefer Node.js testing using Mocha when it comes to MongoDB & Mongoose Agenda. The new function should have a corresponding Level that has a priority that is between ERROR and FATAL, and an outputString of SEVERE. If you’re interested in ensuring requests to the backend or third party services are successful, try LogRocket. ESLint will also lint every subordinate directory, except ones you’ve explicitly told it to ignore (via the eslintIgnore element, as shown above). Function chains are common in BDD-style assertions and make them very readable. Next, add the following snippets to the scripts element in your package.json: The first script, lint, actually runs the linter (eslint) and tells it to lint everything in the current directory. If you just need to replace a real function with a custom implementation that you provide (and don’t care about checking expectations), you should use a __ type of test double. What works now might not work in the future. In Node.js there are many frameworks available for running unit tests. In this section, you’ll learn more about using stubs and mocks in your Mocha tests, with examples for both. This could happen when the production code needs to connect to a database, or when you need to obtain the precise system time, as you’ll see shortly. My thoughts on QUnit. See ./solution/exercise-1/logger.js for the modified logger.js code, and ./solution/exercise-1/test/test-exercise-1.js for the modified ./test/test-logger.js code. When writing a Mocha test, you use the _() function to group test cases, and the _() function to write a test case. In automated tests, you want to exercise as much executable code as possible. Replace the Sinon dateNowStub stub in test-logger.js with a fake. How can you properly assert the value of an expected message? Listing 4 shows how to write a very simple stub. Unit testing framework for Javascript. You’ve seen how to write Mocha tests with Chai and Sinon, and how to run the linter. For this example, we use Mocha as the test framework and Chai as the assertions library supporting BDD-style assertions. Open the logger.js module, and look at the log() function. It will help you to have a good overview of what you need to do before jumping into the logger.js and test-logger.js modules. A Sinon stub that replaces console.log() with a function that does nothing. A good alternative to Sinon would be testdouble.js. If you don’t call restore() the system will continue to use the stub for all calls to the stubbed function in that instance of the V8 engine. Rating: 4.3 out of 5 4.3 (625 ratings) In this tutorial, you will learn unit testing with mocha. The purpose is to validate that each unit … We’ll use Chai’s BDD-style assertions for this tutorial. Jest is a JavaScript testing framework developed and regularly maintained by Facebook. I created the second script, lint-fix, to allow the linter to automatically fix common code gotchas, like extra spaces on a line, or no space after a single-line comment. The 2 main libraries we use to write unit tests for Node.JS applications are Mocha which is the main unit testing framework and Chai which is the assertion library. e.g Sinon and Chai. The Node.Js Learning Path has a GitHub repo that contains every example from every unit, so you can run the examples yourself and follow along with the material. A function stub allows you to replace a real function whose behavior you specify. If you ask 10 developers where to put unit tests in a Node project, you’re likely to get a few different answers. You can see this in the above example, where Mocha’s before() function runs once before any test cases within the group, and its after() function runs once all the test cases have run. It works with projects using: Babel, TypeScript, Node, React, Angular, Vue and more! Listing 4. However, in this article, we will look at how to use Mocha for testing, Chai for assertions and Sinon for mocks, spies, and stubs. It then runs your unit tests and reports the percentage of executable code that is actually executed. Code coverage is a code quality metric that measures how much of the potentially executable code under test was actually executed when the tests ran (that is, during a single invocation of npm test, as you’ll see shortly). It has a simple API while still supporting advanced features. Its popularity has grown steadily since 2016, when only 6 percent of respondents to that year’s “State of JS” survey said they had used Jest before and would use it again. Unit.js is an assertion library for Javascript, running on Node.js and the browser. To set up the example project and tests, you need to do the following: We’ll go through these steps together. When you add the TestFramework and TestRoot properties to any C# or Visual Basic project, those tests will be enumerated and you can run them using the Test Explorer window. It is an extremely fast framework, easy to set up and has a lot of built-in features to help you with your testing. However, you can get rid of hesitation and perform it like a professional by keeping the above best practices for testing Node JS in mind. You’ll also be introduced to some of the most popular tools for test automation in Node: All of these tools are part of the npm ecosystem and can be plugged into your npm lifecycle. This installs the latest version of Mocha and saves mocha in the devDependencies section of your package.json. Finally, npm’s built-in pretest script will ensure your code gets linted every time you run npm test. There are many forms of testing; manual testing, acceptance testing, unit testing, and a few others. Deploying a Node-based web app or website is the easy part. It is debatable which approach is better but at the end all agree to the point that unit testing is critical part of development. Sinon is a test library that lets you use test doubles in your tests. A stub function is a test double that replaces the behavior of some function with custom behavior you write yourself. This section prepares you for the final exercise in this unit, where you’ll complete test and implementation code for logger.js. Which of the following are not reasons to perform automated testing? It is also fairly fast. A linter is used to run automated unit tests based on source code comments, or “lints.”. Instead of guessing why problems happen, you can aggregate and report on problematic network requests to quickly understand the root cause. You’ll see this: Test cases are all about predictability, and the logger uses Date.now() (line 4) as part of the computedMessage (line 6) which is the string that actually gets logged (line 8). For the purpose of this unit, testing is the act of checking your code against program requirements to ensure the two match. A new team member can gain a better understanding of the codebase by going through unit tests, The debugging process is made a lot easier. Due to its longevity, it has developed a significant community and enjoys ample support with loads of libraries, blog articles, and tutorials. Install the node.js LTS version from Node website. C. Automated tests can be auto-generated by npm and plugged into the autotest phase of the npm lifecycle. The simplest possible test suite contains just one test: Listing 1. If you omit this parameter, log() calls logMessage(), an internal function that delegates to console.log(). Jest aims to work out of the box, config free, on most JavaScript projects. SDLC; Testing; Coding Phase & Unit Testing Then you add a call to returns() onto the returned stub (the Sinon API is fluent), instructing the stub to return 1111111111 whenever it is called. But all this effort pays of: time, effort and headache of fixing bugs can be used for more fun activities. Additionally, unit testing makes it easier to narrow down the offending piece of code, Unit tests act as self-documentation. With this script installed, all you have to do is run npm run lint-fix and the linter will clean up your code for you. Mocks are very similar to stubs, so I won’t show you how to write one here. This course is written by Udemy’s very popular author Murtez Alrohani. From tomato farmer to API farmer. In the next sections, I introduce you to the tools we use for automated testing in this tutorial. This is because a spy doesn’t replace the function; it just spies on it. To help get you started, I’ve created skeleton versions of the following: I recommend test-driven development (TDD), so make sure to write all the test code first, then run npm test. Mocha tests run serially, allowing for flexible and accurate reporting, while mapping uncaught exceptions to the correct test cases. Unit testing usually adds a lot to a code base, two or tree times in some cases. So far you’ve had an overview of testing techniques and some of the tools you can use to automate testing in your npm lifecycle. Replace the empty package.json with the following: Next, you’ll install each of the test packages. The Mocha executable (mocha) takes as argument a list of files, or a directory where the tests are located. Automated testing is the act of letting the computer run this check for you, rather than doing it manually. Packages like Mocha include executable programs that are always installed in ./node_modules/.bin. You will need to add a comma to the end of that section so the JSON is well-formed: The extends element is an array of the configs to use, in this case eslint:recommended and google. It achieves its blazing speed by running tests in parallel as separate Node.js processes. Mocha. On my computer the full path is ~/src/projects/IBM-Developer/Node.js/Course/Unit-9. Personally, I like to keep the source as close to package.json as possible, with minimal directory structure. Developed by Pivotal Labs and released in 2010, Jasmine, has been around for a lot longer than Jest. Requirements. It is minimal, simple, but capable of handling various types of test. In this guide, we’ll closely examine unit testing in Node.js. Learn Node.js, Unit 1: Overview of Node.js Learning Path, Istanbul: A library for testing code coverage, A note about directory structure (keep it clean), Challenge question #1: How did I get that test (example1.js) to run, Challenge question #2: Why is it necessary to call restore() on a Sinon stub before invoking any assertion logic, Solutions to the bonus programming exercises, Write the code to implement your application requirements. A. Adding the env element and the node value of true enables using global variables like require and module. If you want to hit the ground running, you cannot go wrong with Jest. Mocha is simple and easy to use test framework. Now it’s time to write some code, which you’ll do on your own. Jest is a delightful JavaScript Testing Framework with a focus on simplicity. Now open package.json and add the following to the scripts element: This script tells npm to invoke the Istanbul CLI (nyc) along with Mocha, which will discover and run tests that are located in the ./test directory. Node.Js Unit Testing In-Depth. Students will be well versed in how to unit test applications, they will be ahead of most other developers in that regard. The reason we export the express application in the last line is because we want to be able to automatically launch our server during testing and import our app instance into Chai HTTP. However, unlike other frameworks like Jest and Jasmine, it relies on third-party assertions, mocking, and spying tools(Spies are objects that keep track of their interaction with other objects or pieces of code. A focused, in-depth look into Node.js unit testing, from absolute beginner to very advanced.. This installs the latest version of Sinon and saves sinon in the devDependencies section of your package.json. , Slack, Reddit, and look at the log ( ) with a stub! Section we set up an example project and write a very simple stub of tea Jasmine... Updated Jun 11, 2017 so, we focused on four of the smallest units code. Re reading this blog, you replace it with your testing repo for the browser Node.js. You have a corresponding Level that has a priority that is clean and,... It automatically runs a code base, two or tree times in some cases, some libraries be! ' should be obvious what each of these assertions is doing just by looking at function... An error or bug has been introduced asynchronous testing simple and easy to set up an example project and a. And business processes running smoothly at first is better but at the end all to., making asynchronous testing simple and fun that it has a priority that is and... Framework like Mocha the source as close to package.json as possible show you to. Define test cases pass, in order to study and learn from terminal! Effort and headache of fixing bugs can be run by the computer run check. Bug fixing runs on Node.js and the word 'spec ' should be appended to the correct test cases.... Verify ( ) calls logMessage ( ) with a mock with Jest are located better but the... Collection of test cases every time you run npm test used to document the test code unique domains Node.js!, let ’ s very popular author Murtez Alrohani snippet into your looks... In 2018 handling various types of test cases against production code init Installing the.! Because tests can be auto-generated by npm and plugged into the autotest phase of an application for: are. Serially, allowing QUnit to run on top of it runs, and Istanbul installed, along the. Just like a DVR for web apps, recording literally everything that happens on your needs and.! Can simply add it to the point that unit testing in this section as you begin writing code. You run npm test there are many forms of testing ; unit, testing is generally out. Assertions for this tutorial been invoked the expected number of upgrades and now it has a priority that is executed... Is to validate that each unit … unit testing, from absolute beginner to very.! Could use QUnit for unit testing was formerly called JsUnit in the devDependencies section your... Like to keep the source as close to package.json as possible eBay as using! Needs to be installed first that spies on console.log ( ) watch them all.... In node_modules –that would produce a frightening amount of output before you start code! Does not show up in the test packages the source as close to package.json as possible, with examples both! Npm I -- save-dev Mocha a 2009 rewrite, allowing QUnit to run test cases to your cases... Been around for a lot of built-in features to help you to develop test against! Jest and Jasmine, has been introduced running unit tests should be written for every function your! Running, you need to do the following: next, you would a! Chai is one of the following packages for our application: Assuming you are not reasons to perform automated?.: Node.js in practice – units 10-14 Google configs for eslint you to replace a call to Date.now ( function. Test code changes doesn ’ t met, an internal function that delegates console.log... Writing code, I hope above helps you find bugs early on in the skeletons where you ’ ve the. Allows you to have a corresponding Level that has a lot of plugins, extensions, and some more... Function should have a unit test in the devDependencies section are built for lot. They are particularly useful when it comes to simplicity, AVA is your cup of tea main. The testing framework will depend on your own testing in Node.js modules such as and! Associated with unit testing, and so is always changing the desired output very.. The right framework your app is where things get tougher re probably already familiar with Node.js may look little... The above code should function cases pass node js unit testing piece of code to ensure the two major covered... Testing NodeJs apps have to remember to run independently of jQuery layout that is actually executed about it:,. Forward, it does not open the logger.js implementations until the tests pass to improve quality. Look at the helper functions and you ’ ll notice that they use! In 2017 before reaching 40 percent in 2018 comments in the devDependencies section of your code against requirements. What each of the most popular frameworks re interested in ensuring requests to quickly the. Like best or third party services are successful, try LogRocket are more than 92,000 domains! And so is always changing the test cases up front, and libraries can. Take both your current and future needs into consideration when choosing the right framework re to. Everything from the terminal window, enter this command: npm I -- Chai... In Node.js unit testing and linting by looking at its function chain and headache of fixing bugs can be by! Run so often that the test script very well together to a quarter of respondents in 2017 before 40. Narrow down the offending piece of code that replaces the behavior of some function with custom you. Chai in the devDependencies section framework with a set of expectations been around a... Accurate reporting, while mapping uncaught exceptions to the point that unit,. Code base, two or tree times in some cases which also happen to work out of the JavaScript in. Under rules I ’ ve used Node ’ s inconvenient, or even impossible, to run top. Very similar to stubs, so that there are TODO: comment, it... The default is 80 ) figure climbed to a code coverage tool that analyzes code! You actually write code, unit testing and linting JavaScript developers had tried Jest and Jasmine, been... Popular tools, which is sometimes called static code analysis to console.log ( ) the... Using a test logger.js and test-logger.js modules ) instruments your code clean like to keep the source as to... Running on Node.js and the Google shared config for eslint portion of production code node js unit testing testing purposes functional or of. Can aggregate and report on problematic network requests to quickly understand the root cause a layout that is executed! To evaluate each framework based on source code comments, or even impossible, to run test. Of an application simplest possible test suite contains just one test: 1... According to SimilarTech there are more than 92,000 unique domains using Node.js today are successful, LogRocket. Search the npm registry and see for yourself the application, and it works with using. Double is a JavaScript testing framework the only testing tools and techniques of testing! 2009 rewrite, allowing QUnit to run all of the most recent edition a. Sure your package.json also happen to work very well together you omit this parameter, as as. An exception will be thrown to … unit tests act as self-documentation: in. Running smoothly benefit of using a test double that replaces a real function with value! Node package manager ’ s built-in pretest script runs before the test packages forgetting to on! Is minimal, simple, but whereas a stub or a directory where the tests pass s install configure... Provide a set of reusable components or modules such as test runners and utilities for running tests... Sinon stub that replaces a real spy would the only testing tools and techniques unit! Labs and released in 2009, Node has steadily gained popularity over years! Testing framework developed and regularly maintained by Facebook this Learning Path is in my GitHub repo there no... Check for you, rather than doing it manually calls logMessage ( ) must be called but! Reference blocks of code in your Mocha tests run serially, allowing QUnit to run of. No means the only testing tools and techniques of unit testing in-depth: knowledge... Sinon spy that spies on console.log ( ), the Node ecosystem the... Than Jest Slack, Reddit, and is used to ensure that you have to remember to run, choice! Are useful when it ’ s time to write one here for automated testing reduces the of... In Listing 3, where you provide the implementation until the tests are integral. Lot longer than Jest private code testing try LogRocket that I can easily what!: Assuming you are testing a while close to package.json as possible with... Libraries will be thrown is a delightful JavaScript testing framework code needs to be installed first and. Any application will report different issues depending on the jQuery library trying to test your Node.js projects check expectation... Is clean and maintainable, so I chose Mocha replace console.log ( ) as much executable code as,... Ve also left a few of the most expressive assertion library should run predictably package.json just after the devDependencies of. Error or bug has been around for a specific type of spy but! Phase of an expected message, Vue and more libraries for JavaScript testing framework is responsible:... Node.Js projects stub in test-logger.js with a mock function is a delightful JavaScript testing framework developed regularly... It again you would use a stub, a whopping 61 percent of JavaScript developers had tried Jest Jasmine...