Javascript Unit Testing

Exercising unit testing with Javascript (Mocha + Istanbul)

Motivation

Wanting to exercise a little bit of Test Driven Development in Javascript, I got this problem of, in an 'ocean' composed by 'water' (0's) and 'land' (1's), to find the largest 'island', that is, the longest sequence of 1's that are adjacent to each other. For that, the algorithm (the simplest I could imagine) was easy to implement, and I have used only the simplest features of the language. The new things (for me) here are the testing framework Mocha in order to able to run it within Node. To get code coverage on the tests, I have used Istanbul.

THAT IS A LOT OF NAMES!!!!!!

Indeed.

I really jumped into Javascript about one year ago. Then, I tried to learn the simplest things and found too much names to look at. And I wasn't alone in that.

But since starting to work with it, my approach became to:

a) Stick to the basics, and

b) Just use the recommended tools, or the first you get on with good docs.

This way, making this small project became very simple.

The road for this one

At first, I wanted to run these tests on my machine's terminal, not in a browser. For this, Node.js was the choice, as it is a Javascript platform. Then, I wrote the code as the specification required, being it a function that took three parameters (matrix, number of rows, number of columns). This wasn't necessary, as length of an array is an attribute of it in Javascript, but the specs needed to be satisfied. Also, I had to pass on the reference to the matrix, and it would be better off as an instance attribute for a class, but again the specification (define a function for solving this) was made.

After deciding the platform and basic structure, I needed a testing framework. Looking in the internet, the first one to come was Unit.js. But to use Unit.js I needed a test runner, that was Mocha. Then I found that Unit.js is an assertion library, and as I am sure that are use cases that it fills best, basic assertion would be fine for me, so I used them. Then, I remembered that I have used test coverage in another project. Code coverage helps looking at how much the code is tested, so why not? For that, another query made me find Istanbul.

With all set, I just needed to take a look the pages, that had really good info on how to write the tests and run them, and proceeded with writing the program with the tests.

Commands

For those who are not well acquainted with the state of Javascript at this moment, the way I did this was to:

a) Have Node installed

b) Have npm installed. ANOTHER NAME, I KNOW. That is the Node package manager. Just that

c) Install Mocha: npm install -g mocha. The '-g' stands for 'global install'. This is not the best practice, since one may want to only install it locally for a project, but I wanted to keep things simple on this one. I was already taking too much time on tooling instead of coding

d) Install Istanbul: npm install -g istanbul

e) Just run: istanbul cover _mocha tests

Last thoughts

After that I got all tests passing and a good code coverage, a good thing was to check the code itself for Javascript styling and code correctness. Static code analyzers are old friends for programmers, and in scripting languages they shine. This way, I just used one I knew, jshint - THIS IS THE LAST NEW NAME HERE I PROMISE -, and used it to check:

jshint largestisland.js

On installing jshint? Unsurprisingly: