If you don't have Node.js installed, you may want to use nvm and install it. Once node and npm commands exist on your computer, install Dredd globally:
$ npm install -g dredd
Get API_KEY from google to use Geocoding API. Replace API_KEY with your own key from google in secret-config.json (refer secret-config-sample.json).
To test the API use
$ dredd apiary.apib --hookfiles=./hooks.js