Apple Hardware Test (AHT) not progressing on MacBook Air 11" Mid 2013

I've MacBook Air 11" Mid 2013 and I recently clean installed OS X Yosemite on it. The startup was real slow. It took more than 30 seconds to display the apple logo after pressing the power key so I decided to run Apple Hardware Test.

but the problem is that it won't progress. the screen displays "internet recovery. this may take a while" and it asks to connect to a wifi connection. then i selected my wifi connection but it won't progress from there.

P.S. I've never performed Apple Hardware Test before but I've done a lot of research on the internet about it. After selecting WiFi connection, it should prompt me for the password but it won't.

It won't progress from here...HELP!!!