Unless you have the most recent MacBook Air, you have no way to test 802.11ac access points. Unfortunately, there is no way to change out the built in WiFi card on your existing Mac or enable 802.11ac with a software upgrade. Thankfully, there is a third-party solution from Edimax. The Amazon product page says it's not compatible with OS X, but there is a driver available on the actual Edimax website. It's certainly not ideal to use a dongle for WiFi access, but it's nice that there is a solution for testing purposes. I picked one up recently and can confirm that it works fine on OS X 10.8.5. You likely won't see as good of performace on a USB card as you would with a built-in card, but it should give you a decent idea of what you can expect.