A guide to mocha's describe(), it() and setup hooks

Mocha is a wonderful testing framework for node.js, however the documentation seems to be lacking.

When I first begin to write in Mocha, I had many questions:

what exactly does describe() do?
what is the effect of nesting describe() multiple levels?
is describe() a test suite, and it() a test case?
where should I place before() and after() hooks?

I didn’t find the answer online, hence I simply test it out myself.

This gist is the javascript that explains the questions I had. Much clearer now :)

I also used docco to generate a more-pleasing-to-read documentation for the gist.

Sorry but I didn’t host the docco documentation, but you could still read the javascript in it’s purest form:

// # Mocha Guide to Testing // Objective is to explain describe(), it(), and before()/etc hooks // 1. `describe()` is merely for grouping, which you can nest as deep // 2. `it()` is a test case // 3. `before()`, `beforeEach()`, `after()`, `afterEach()` are hooks to run // before/after first/each it() or describe(). // // Which means, `before()` is run before first it()/describe() // ----------------------------------------------------------------------------- // should.js is the preferred assertion library var should = require('should'); // **Only 1 test case (in a nameless test suite)** it('birds should fly', function(){ /** here.should.be.tested * However, as long as no error within a it(), * it() is considered PASSED */ }) // **Only 1 test case, but nested 3-level deep** // describe() are: // - commonly known as test suites, which contains test cases // - merely groups, and you can have groups within groups describe('galaxy', function(){ describe('earth', function(){ describe('singapre', function(){ it('birds should fly', function(){ /** ... */ }) }) }) }) // **2 test cases in 1 test suite** // A common scenario. describe('singapre', function(){ it('birds should fly', function(){ /** ... */ }) it('horse should gallop', function(){ /** ... */ }) }) // **Run once before the first test case** describe('singapre', function(){ before(function(){ console.log('see.. this function is run ONCE only') }) it('birds should fly', function(){ /** ... */ }) it('horse should gallop', function(){ /** ... */ }) }) // **Run once before each test case** describe('singapre', function(){ beforeEach(function(){ console.log('see.. this function is run EACH time') }) it('birds should fly', function(){ /** ... */ }) it('horse should gallop', function(){ /** ... */ }) }) // **2 test suites in a big test suite** // A common scenario. describe('earth', function(){ describe('singapre', function(){ it('birds should fly', function(){ /** ... */ }) }) describe('malaysia', function(){ it('birds should soar', function(){ /** ... */ }) }) }) // **before() can be applied to describe() too** describe('earth', function(){ before(function(){ console.log('see.. this function is run ONCE only, before first describe()') }) describe('singapre', function(){ it('birds should fly', function(){ /** ... */ }) }) describe('malaysia', function(){ it('birds should soar', function(){ /** ... */ }) }) }) // **beforeEach() can be applied to describe() too** describe('earth', function(){ beforeEach(function(){ console.log('see.. this function is run EACH time, before each describe()') }) describe('singapre', function(){ it('birds should fly', function(){ /** ... */ }) }) describe('malaysia', function(){ it('birds should soar', function(){ /** ... */ }) }) })

Junda Ong

A Guide to Mocha's Describe(), It() and Setup Hooks

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