Accessing Apple Hardware Tool on MacBook Air 2010 running Yosemite
Your AHT feature will have been lost when you upgraded to Yosemite.

You can restore it by inserting the Applications Install disc that was supplied with your computer and typing the following command, putting in the actual name of the disc where indicated...

sudo cp -R /Volumes/[name of disc]/System/Library/CoreServices/.diagnostics /System/Library/CoreServices


You will of course be able to run the diagnostics directly from the install disc.


Actually read the question properly and of course your Air doesn't have an optical drive - did it come with any re-installation media? If not you now know where the actual test file should go, if anyone can supply you with the required file