When using JUnit and Maven in Java, one can have separate property files for src/main and src/test. This allows different configuration for code and tests, having Maven to manage the resources by using Java classpath.

Is there a similar way in Javascript code run by Node.js? I use Mocha for unit-testing and Grunt for task management.

Code example for script.js:

var config = require('./config/dev/app.js');

exports.getFileName = function() {
    return config.fileName; // returns 'code.txt'
}

What I need is to make the script.js use different config file when being required in a test.js unit test like this:

var assert = require('assert');
var s = require('./script.js');

describe('Test', function () {
    it('should use different config file', function() {
        assert.equal('test.txt', s.getFileName());
    });
});

Is there a way to use different configuration ./config/test/app.js in the script.js without having to alter the code of script.js? What I really try to avoid is to adjust the code to support unit tests. Instead, I want to achieve similar functionality such as mentioned Java classpath.

I have not found any elegant solution out there on the web so I have implemented and published my own. Check it out here: https://npmjs.org/package/app-config

Using the app-config plugin, only the script.js needs to get changed this way:

var config = require('app-config').app;

exports.getFileName = function() {
    return config.fileName; // returns 'code.txt'
}

The app needs to be run this way for example

1. NODE_ENV=dev node script.js
2. NODE_ENV=unitTest mocha test.js

Depending on the NODE_ENV environmental variable, the right set of configuration files will be loaded by the app-config plugin.