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Writing unit tests with Mocha

From: Node.js Essential Training

Video: Writing unit tests with Mocha

Testing code is much easier when unit testing frameworks are used. In addition to frameworks, there are also unit testing tools available that can be used with any frame work. In this video, we'll install some of these tools, then write some unit tests. First go to the exercise files, and then open up chapter six and video four. Copy the start folder the desktop, then go to Terminal. I'm going to change directory to the start folder. And now I'm going to type npm install.

Writing unit tests with Mocha

Testing code is much easier when unit testing frameworks are used. In addition to frameworks, there are also unit testing tools available that can be used with any frame work. In this video, we'll install some of these tools, then write some unit tests. First go to the exercise files, and then open up chapter six and video four. Copy the start folder the desktop, then go to Terminal. I'm going to change directory to the start folder. And now I'm going to type npm install.

So now that I've installed the existing modules, I'm also going to install three more modules that I'm going to use for unit testing. They're called Mocha, Should, and Supertest. Now these modules are only intended for the unit testing of our application, and they're not intended to be a permanent part of the normal operation of the application. So when we install these modules, we're going to tell npm that we want to place them in a specific part of our package.json file. To do that, we're going to use the flag called save dev.

So, now I'm going to install these three modules with save dev. So, to do that, I'm going to type dash dash save and then dash dev. I'll do that for Mocha, and then I'm also going to do it for Should and Supertest. So I'm going to press the up arrow on my keyboard, and then just change Mocha to Should, and then I'm going to do the same for Supertest. Now before we move on, let's take a look at that package.json file. I'm dragging the start folder into sublime text, and now I'm opening up package.json.

You'll notice that on line 12, we have a new property called devDependencies. And it's an object that includes Mocha, Should, and Supertest. This way our package.json file is identifying these three modules as ones we're using for reunit testing. Let's take a closer look at these modules. First there's Mocha. Mocha is a unit testing framework, that I'm fond of. It allows you to find a sweet of tests you want to run, then provides a done function you can call with each individual test is done.

Since a lot of code in JavaScript is asynchronous, having this function available for a call back is extremely helpful. Another tool I use for unit testing is Should. The module Should extends the native object prototype with functions for asserting values. Normally, extending the native object prototype is a dangerous thing to do, since it effects the entire JavaScript run time environment. But since the change is only going to last during the lifetime of the unit test, it's not as much of a concern to me.

And finally, since we're testing a web application, I'm also going to use Supertest. The Supertest module lets you simulate HTTP requests to your express application. What's nice about it is that you don't have to fire up the application on the specific server port. Supertest just tests the routes you've defined in your application. So let's go back to the code. I'm going to open up the Start folder in Sublime Text. And then I'm going to go to test and flightspec.js. For now, I'm going to require Should and Supertest.

We're going to use them later. And now let's write some unit tests. To start a suite of unit tests in Mocha, you use the describe function. The first argument you pass into describe is a label for this unit test suite I'm going to call this flights. The second argument you pass into describe is an anonymous function. Within this function, is where you write your individual unit tests. So let's write a couple of tests now. To write a test, you call the it function.

The first argument you pass is a label describing what it should do. So I'm going to say it should pass. And then the second argument you pass in is a function. That function is provided with one argument called done. So I'm going to call that done function right away. So this unit test is going to pass, because we're not really even testing anything, we're just calling done and it's going to pass. Now let's write another unit test. In this unit test, I'm going to throw an exception.

So even though I'm calling done at the end, this throw key word should throw an exception which should break the unit test. So now that we've written a couple of unit tests, let's run them. So there are two ways that we can run these unit tests. The first way is we can modify package.json and in the script section, we can add a test property. And then in that test property, we'll tell npm how to unit test this module. An easier way to do it right away though is to install Mocha as a global module, and then run the Mocha command from Terminal.

So let's do that now. I'm going to install Mocha as a global module by typing npm install -g Mocha. This fails though, because I'm not an administrator on this computer, and the Node modules folder is protected. So to fix this, I'm going to type sudo at the beginning. I've pressed up on the keyboard to get the last command, and now I'm just going to preface this command with pseudo. So it asks for my password, and now it installs Mocha. So let's run these unit tests.

I'm at the root of my application, and I have a folder named Test, so if I type Mocha here, it will run the unit tests. So it's saying I have one passing test, and one failing test. The failing test is because we're throwing that error. So if I comment out the throw key word, and I run the unit test again by pressing up on the keyboard, and pressing Return, I now have two passing unit tests. A unit testing framework makes it easy to write and organize your unit tests. Unit testing frameworks, like Mocha, are flexible, in that you can use any other tools you'd like along with them.

In the next video, we'll use the Supertest module to simulate HTTP requests.

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This video is part of

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Node.js Essential Training

52 video lessons · 12311 viewers

Joseph LeBlanc
Author

 
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  1. 3m 9s
    1. Welcome
      42s
    2. What you should know before watching this course
      57s
    3. Using the exercise files
      47s
    4. Using the challenges
      43s
  2. 18m 50s
    1. Why use Node.js?
      2m 1s
    2. Choosing a Node.js installation process
      4m 56s
    3. Installing Node.js on the Mac
      2m 5s
    4. Installing Node.js on Windows
      1m 43s
    5. Installing Node.js via Node Version Manager on Ubuntu Linux
      4m 45s
    6. Installing Node.js via Node Version Manager on a Mac
      3m 20s
  3. 13m 54s
    1. Exploring language additions to the V8 JavaScript engine
      3m 38s
    2. Understanding require() and modules
      6m 39s
    3. Understanding callback execution in the event loop
      3m 37s
  4. 12m 23s
    1. Initializing Node.js projects
      2m 37s
    2. Finding an NPM
      3m 30s
    3. Maintaining projects using the npm command
      6m 16s
  5. 21m 4s
    1. Creating modules with getters and setters
      6m 33s
    2. Understanding module caching and scopes
      6m 15s
    3. Implementing JavaScript creational patterns
      5m 8s
    4. Challenge: Leveraging module caching
      55s
    5. Solution: Leveraging module caching
      2m 13s
  6. 32m 27s
    1. Starting Express applications
      3m 42s
    2. Handling GET requests returning JSON
      3m 26s
    3. Navigating large datasets using request variables in routes
      5m 4s
    4. Modifying data through PUT requests
      4m 32s
    5. Supplying middleware to modify HTTP response headers
      4m 37s
    6. Generating HTML views in Jade
      8m 9s
    7. Challenge: List all records as JSON
      37s
    8. Solution: List all records as JSON
      2m 20s
  7. 25m 37s
    1. Evaluating unit testing methodologies
      3m 8s
    2. Isolating existing code for testing
      6m 47s
    3. Supplying helpers for test data
      2m 35s
    4. Writing unit tests with Mocha
      6m 5s
    5. Simulating HTTP requests with SuperTest
      7m 2s
  8. 28m 45s
    1. Connecting to MongoDB via Mongoose
      4m 16s
    2. Defining schemas for collections in Mongoose
      3m 47s
    3. Querying MongoDB collections
      5m 32s
    4. Persisting Express sessions through MongoDB and mongo-connect
      7m 6s
    5. Logging in to Express applications using Passport
      8m 4s
  9. 21m 47s
    1. Controlling the built-in REPL
      4m 18s
    2. Constructing a custom REPL
      5m 40s
    3. Receiving command-line arguments with Optimist
      6m 14s
    4. Building command-line tools
      3m 35s
    5. Challenge: Launch a custom REPL from a command
      41s
    6. Solution: Launch a custom REPL from a command
      1m 19s
  10. 15m 46s
    1. Emitting events and attaching listeners
      5m 32s
    2. Streaming chunked data through readable streams
      2m 33s
    3. Controlling readable streams
      1m 52s
    4. Piping readable data into writable streams
      2m 10s
    5. Handling duplex streams over TCP
      3m 39s
  11. 4m 6s
    1. Deploying projects to cloud hosting services
      2m 36s
    2. Finding Node.js resources
      1m 30s

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