Using mocha programmatically

There are a lot of reasons why you might want to automate running the tests using mocha. Using the command-line can run into some problems if you want to load specific files, for example.

Here is an example of using mocha programmatically:

var Mocha = require('mocha'),
    fs = require('fs'),
    path = require('path');

// First, you need to instantiate a Mocha instance.
var mocha = new Mocha;

// Then, you need to use the method "addFile" on the mocha
// object for each file.

// Here is an example:
fs.readdirSync('some/dir').filter(function(file){
    // Only keep the .js files
    return file.substr(-3) === '.js';

}).forEach(function(file){
    // Use the method "addFile" to add the file to mocha
    mocha.addFile(
        path.join('some/dir', file)
    );
});

// Now, you can run the tests.
mocha.run(function(failures){
  process.on('exit', function () {
    process.exit(failures);
  });
});

Set options

There are two ways to set the options to run the tests.

Firstly, you can set these options in the constructor object:

var mocha = new Mocha({
    ui: 'tdd',
    reporter: 'list'
});

Here is the list of these options:

• grep
• ui
• reporter
• timeout

Secondly, on the mocha object, there are some chainable methods allowing you to change some more options.

Here is an example:

// Change the reporter to "list" before running the tests
mocha.reporter('list').run();

// Change the UI to "tdd" before running the tests
mocha.ui('tdd').run();

// Or do both changes before running the tests
mocha.reporter('list').ui('tdd').run();

Here is the list of all these chainable methods:

• reporter(): set the reporter.
• ui(): set the ui.
• grep(): add regex to grep.
• invert(): invert the grep.
• ignoreLeaks(): ignore global leaks.
• growl(): enable growl support.
• globals(): ignore globals.