var assert = require('assert');
var http = require('http');
var mm = require('mm');

var obj = {
  foo: function () {
    console.log('original foo called');
  }
};
mm(obj, 'foo', function () {
  console.log("mocked foo called");
});
obj.foo();

//Manually override the http.request for certain purpose.
http.request = function (option, callback) {
 throw new Error('Never want to send request out');
} 

mm.restore();
try {
  http.get({ path: '/foo' }, function (res) {});
} catch (e) {
  //assert here failed, because the restore made the overriding above invalid
  assert.equal(e.message, 'Never want to send request out');
}