DenetmenBundle is a Symfony2 bundle that allows testing of routes and responses. It informs you when pages return errors, checks response times and types, and validates response content. It can test GET requests, mock parameters, and validate responses. To use it, add the bundle to your composer.json file, register the bundle, and create a configuration file to define routes to test and validation rules. The console command runs the tests and can filter routes or send alerts on errors.