function snake_case(name, separator) {
  separator = separator || '_';
  return name.replace(SNAKE_CASE_REGEXP, function(letter, pos) {
    return (pos ? separator : '') + letter.toLowerCase();
  });
}
@name angular.getTestability
@module ng
@description
Get the testability service for the instance of Angular on the given
element.
@param {DOMElement} element DOM element which is the root of angular application.