The simulation mode allows you to verify if the browser is correctly redirected to a set of proxies or use direct mode according the source IP address, the browser and the destination url.
On the WPAD rules, click on the button “Test your rules”
Set the destination URL, the IP address of the client and optionally the User Agent string ( if you have created rules based on User-Agent string).
Click on the Simulate button, you will see results on the left part if the browser will use a proxy or will use a direct connection.