Unfortunately, using just assertions isn't a very organized way of testing and describing behavior. To deal with this we are going to use a set of tools that help us organize our assertions and print better errors when they fail.
npm install -g mocha
mkdir test
subl test/test.js
It is also best practice to add your testing frameworks to your package.json.
npm install --save-dev mocha
We use --save-dev because it used only when developing our application, and --save will add it to our general list of dependencies, which would be weird because we should not need a testing framework to get our project running.
From here we will break down the example on Mocha's homepage. Let's paste the following into our test/test.js file.
test/test.js
// the assert library built into node
var assert = require("assert");
/*
describe doesn't really do much,
beyond running the code in the
function it's given
*/
/*
note we are using describe to
group a set of tests all related
to the Arrays
*/
describe('Array', function(){
/*
here we use a describe to
indicate another group of
tests, but yet again it isn't
doing anything really
*/
/*
we are trying to describe a
group of tests related to
the Array#indexOf method
*/
describe('#indexOf()', function(){
/*
the it method does all the work
in mocha, it takes a message to
print if the test fails for a
behavior
*/
/*
here we are trying to that
Array.indexof behaves well
when values are not in the
array.
*/
it('should return -1 when the value is not present', function(){
// We are using assert to throw errors if something is wrong
assert.equal(-1, [1,2,3].indexOf(5));
assert.equal(-1, [1,2,3].indexOf(0));
})
})
})
You might be hating the how unintuitive using assert feels. Luckily, their are more intuitive libraries that stress readability that do what assert does.
Here we see that Chai comes in three different flavors:
- should
- expect
- assert
The cool thing is that assert looks like what we've already been using, but our focus if going to be on using the expect library. This is because using mocha with chai's expectations is going to look a lot like Rspec when we get to ruby.
To get chai installed we are going to run
$ npm install --save-dev chai
This saves it to our devDependencies list which isn't required to actually run or project. For documentation on how to write assertions with chai read the following, chai api.