How to spy on node's require() w/ sinon.js

gistfile1.js

//If you need to spy or stub the global require function in node.js, don't try to spy on the require function itself..you aren't going //to be successful.
//Instead, spy on the require.extensions object like so:

var spies = {};
spies.require = sinon.spy(require.extensions, '.js');

//Then when you need to assert you can do stuff like:

spies.require.firstCall.args[1].should.include("path/to/some/module");

//Don't forget to clear cached modules if you want to make sure they are called...
//I'm sure there are other ways to do this, but if you want a module or set of modules cleared during tear-down, you can try
//something like this:

_.each(require.cache, function(cachedModule, indx) {
    if (indx.indexOf("path/to/some/module") >= 0) {
        delete require.cache[indx];
    }
});

require.extensions is deprecated now