Web Automation Practice

Instructions: Test interaction with a background script (Web Worker).

1. Click the "Start Calculation" button. This sends a message to a web worker.
2. The worker will perform a "heavy" calculation without freezing the main page.
3. Wait for the worker to post a message back with the result.

Validation: Your script should verify that the output box displays the message "Calculation complete! Result: 5000000000".