In this lesson we'll setup testing for the project using the Mocha test framework
Mocha is a test framework for NodeJS.
Let's install mocha locally (using the --save-dev option to add it to package.json as a package dependency):
> npm install mocha --save-dev
npm WARN package.json greet@0.0.0 No repository field.
npm WARN package.json greet@0.0.0 No README data
npm http GET https://registry.npmjs.org/mocha
npm http 200 https://registry.npmjs.org/mocha
npm http GET https://registry.npmjs.org/mocha/-/mocha-1.18.2.tgz
npm http 200 https://registry.npmjs.org/mocha/-/mocha-1.18.2.tgz
...
mocha@1.18.2 node_modules/mocha
├── diff@1.0.7
├── debug@0.7.4
├── growl@1.7.0
├── commander@2.0.0
├── mkdirp@0.3.5
├── jade@0.26.3 (commander@0.6.1, mkdirp@0.3.0)
└── glob@3.2.3 (inherits@2.0.1, graceful-fs@2.0.3, minimatch@0.2.14)
Now mocha is installed in the local ./node_modules/mocha directory.
And in package.json you can see the development dependencies:
"devDependencies": {
"mocha": "^1.18.2"
}
Executables installed by node packages are available in ./node_modules/.bin/:
$ ./node_modules/.bin/mocha --version
1.18.2
This is actually a symbolic link to a file in ./node_modules/mocha:
$ ls -l ./node_modules/.bin/mocha
./node_modules/.bin/mocha -> ./node_modules/mocha/bin/mocha
If we want to run the locally installed mocha executable as mocha instead of ./node_modules/.bin/mocha, we need to add ./node_modules/.bin to the PATH environment variable:
$ export PATH=./node_modules/.bin:$PATH
$ which mocha
./node_modules/.bin/mocha
$ mocha --version
1.18.2
Add export PATH=./node_modules/.bin:$PATH to ~/.bashrc if you want to be able to run locally installed npm executables in the future.
The scripts key is used to specify tasks that the package can run (see: list of available tasks). In package.json we have:
{
"name": "greet",
...
"scripts": {
"test": "mocha"
},
...
}In this example, the test task runs the mocha command. We can try running the test:
$ npm test
> greet@0.0.0 test /Users/howard/workspace/node-bootcamp/greet
> mocha
/Users/howard/workspace/node-bootcamp/greet/node_modules/mocha/bin/_mocha:432
if (!files.length) throw new Error("cannot resolve path (or pattern) '"
^
Error: cannot resolve path (or pattern) 'test'
...
This error is because we don't have the test directory. Let's create it:
$ mkdir test
$ npm test
npm test
> greet@0.0.0 test /Users/howard/workspace/node-bootcamp/greet
> mocha
0 passing (1ms)
Cool it works now.
The Mocha test framework allows you to write your tests in many different styles. We'll choose to write our tests using the BDD style and the "expect" syntax of the Chai assertion library.
An example test looks like:
var expect = require("chai").expect;
describe('Array', function(){
before(function(){
// ...
});
describe('#indexOf()', function(){
it('should return -1 when not present', function(){
expect([1,2,3].indexOf(4)).to.equal(-1);
});
});
});Install both mocha and chai as development dependencies:
$ npm install mocha chai --save-dev
...
chai@1.9.1 node_modules/chai
├── assertion-error@1.0.0
└── deep-eql@0.1.3 (type-detect@0.1.1)
mocha@1.18.2 node_modules/mocha
├── diff@1.0.7
├── debug@0.7.4
├── growl@1.7.0
├── commander@2.0.0
├── mkdirp@0.3.5
├── jade@0.26.3 (commander@0.6.1, mkdirp@0.3.0)
└── glob@3.2.3 (inherits@2.0.1, graceful-fs@2.0.3, minimatch@0.2.14)
There's no test yet:
$ mocha
0 passing (1ms)
The mocha command find files that match the pattern test/*.js and run the tests in those files. Let's Create the first test file at test/greet_spec.js:
var expect = require("chai").expect
describe('greet', function(){
it("is a dummy success case", function(){
expect(1).to.eql(1);
});
});Let's run mocha (with the -R option to get more detailed output):
$ mocha -R spec
greet
✓ is a dummy success case
1 passing (6ms)
Implement: Write the actual test cases for the greet function. There are two cases:
- your test file should require the greet module
- should greet a person by name
- should greet a person flirtatiously if drunk
Hint: Chai BDD API reference.
The test output should look like:
$ mocha -R spec
greet
✓ should greet a person by name
✓ should greet a person flirtatiously if drunk
2 passing (6ms)
As your test suite grows bigger into multiple files, you might find it helpful to be able to share code across all files.
In our case instead of having to require expect in every test file, let's create a spec helper to load it.
Remove var expect = require("chai").expect from test/greet_spec.js. The test suite should now fail:
$ mocha
․․
0 passing (4ms)
2 failing
1) greet should greet a person by name:
ReferenceError: expect is not defined
2) greet should greet a person flirtatiously if drunk:
ReferenceError: expect is not defined
In test/support/helper.js add the following:
global.expect = require("chai").expect;Let's run mocha again with the --require option to load the helper:
$ mocha --require test/support/helper
․․
2 passing (4ms)
It works.
Question: How is var expect = ... different from global.expect = ...? Does it work if in helper.js you use var expect = require("chai").expect;
Hint: See global
It's cumbersome to have to type --require test/support/helper everytime you run a test. You can set mocha's default options by creating the mocha.opts in the test directory.
In test/mocha.opts add:
--require test/support/helper
--reporter spec
Now you can run mocha without specifying options:
$ mocha
greet
✓ should greet a person by name
✓ should greet a person flirtatiously if drunk
2 passing (6ms)
You can also run the test suite as an npm task:
$ npm test
npm test
> greet@0.0.0 test /Users/howard/workspace/node-bootcamp/greet
> mocha
greet
✓ should greet a person by name
✓ should greet a person flirtatiously if drunk
2 passing (6ms)
If you'd like to gain more experience using Mocha, you are encouraged to read Better CoffeeScript Testing With Mocha is a great tutorial that guides you through building a todo list using TDD.
It uses the should syntax instead of expect.