Node.jsのテストで特定の関数をモックと置き換える ref: http://qiita.com/okunishinishi@github/items/fe22839a72a5717a4982

file0.js

// nodeunitのテストケース

exports.setUp = function(done){
    // console.logを何もしない関数と置き換える
    console.log = function noop() {
    }
    done();
};

file1.js

// nodeunitのテストケース

var log;
exports.setUp = function(done){
    // console.logを何もしない関数と置き換える
    log = console.log;
    console.log = function noop() {
    }
    done();
};
exports.tearDown = function(done){
    // console.logを戻す
    console.log = log;
    done();
};

file2.js

// Disable console.log before test started.
exports.setUp = function (done) {
    function mockLog() {
    }

    // Inject `mockLog` as `console.log`.
    injectmock(console, 'log', mockLog);

    done();
};

// Disable console.log before test done.
exports.tearDown = function (done) {
    // Restore all injected.
    injectmock.restoreAll();

    console.log('Now I am back!');

    done();
};

file3.js

/**
 * Inject mock functions to node modules.
 * @memberof injectmock
 * @inner
 * @constructor Injector
 */
function Injector() {
    var s = this;
    s.injections = [];
}
Injector.prototype = {
    /**
     * Inject a mock to a module.
     * @param {object} module - Module to injected.
     * @param {string} key - Injection key.
     * @param {*} value - Value to inject.
     * @returns {*} - Returns self.
     */
    inject: function (module, key, value) {
        var s = this;
        s.injections.unshift({
            module: module,
            key: key,
            delete: !module.hasOwnProperty(key),
            origin: module[key],
            value: value
        });
        module[key] = value;
        return s;
    },
    /**
     * Restore injected.
     * @param {object} module - Module to injected.
     * @param {string} key - Injection key.
     * @returns {*} - Returns self.
     */
    restore: function (module, key) {
        var s = this;
        var index = s._indexOfInjection(module, key);
        var injection = s.injections[index];
        if (injection) {
            if (injection.delete) {
                delete module[key];
            } else {
                module[key] = injection.origin;
            }
            s.injections.splice(index, 1);
        } else {
            // Do nothing.
        }
        return s;
    },
    /**
     * Restore all injected.
     * @returns {*} - Returns self.
     */
    restoreAll: function () {
        var s = this;
        while (s.injections.length) {
            var injection = s.injections[0];
            s.restore(injection.module, injection.key);
        }
        return s;
    },
    _indexOfInjection: function (module, key) {
        var s = this;
        for (var i = 0, len = s.injections.length; i < len; i++) {
            var injection = s.injections[i],
                hit = (injection.key === key) && (injection.module === module);
            if (hit) {
                return i;
            }
        }
        return -1;
    }
};

file4.js

function context() {
    var injector = new Injector();
    var inject = injector.inject.bind(injector);
    inject.restore = injector.restore.bind(injector);
    inject.restoreAll = injector.restoreAll.bind(injector);
    return inject;
}

var injectmock = context();
module.exports = injectmock;

file5.txt

var inject = injector.inject.bind(injector);

file6.txt

npm install injectmock --save-dev

file7.js

var injectmock = require('injectmock');

// Disable console.log before test started. 
exports.setUp = function (done) {
    function mockLog() {
    }

    // Inject `mockLog` as `console.log`. 
    injectmock(console, 'log', mockLog);

    done();
};

// Disable console.log before test done. 
exports.tearDown = function (done) {
    // Restore all injected. 
    injectmock.restoreAll();

    console.log('Now I am back!');

    done();
};