The "DO Deck Edge Extension" is the web plugin component of the DO Deck platform. Its functionality involves recording user interactions within the browser and transmitting the recorded information back to the DO Deck platform through a WebSocket. The testing procedure is as follows:

1. Install the plugin package.
2. Click on the plugin.
3. Click the "Start Recording" button, and your mouse and keyboard actions on the browser will be recorded.
4. Perform various browser operations.
5. Click the "Stop Recording" button.
6. This extension will transmit your recent actions via WebSocket back to the Desktop app. If you wish to view them, you can start a WebSocket server locally, listening at ws://localhost:8999.