gistfile1.js

// FUCK HEADS https://github.com/caolan/nodeunit#tests-run-in-series
// No ->
var _readFile = fs.readFile;
fs.readFile = function(path, callback){
    // its a stub!
};
// test function that uses fs.readFile

// we're done
fs.readFile = _readFile;

// Yes
// Better -> but could be improved, if you create a wrapper for IO.
var FileProvider = {
  get: function(path, callback) {
    return fs.readFile(path, callback);
  }
};

var MockFileProvider = {
  get: function() {
    return // My stubby!
  }
}

var file = FileProvider.get(path, callback);
// or 
var file = MockFileProvider.get(path, callback);

Essentially they're testing the wrong code. There should be a mocking lib setup to spy or at least mock the fs.readFile. Don't method swizzle it.

Although it's fun to see who is using it :-)