You need node.js, npm, grunt and Mozilla Addon-SDK to work on Mephisto scripts.
Prepare your environment:
# Once you activated your SDK virtual-env
# Update submodules
git submodule update --init --recursive
# Install npm deps
npm install
It's easier to launch Mephisto with dedicated "mephisto" grunt task.
To launch server:
grunt mephisto:scripts/server.js
# or shortcut:
grunt runserver
To launch a test script:
grunt mephisto:scripts/launch-tests.js:"http\:google.com/"