How to I access the A/B testing features after upgrading to 4.6?
The A/B testing features come with two menu items. For me, they weren't showing up for some reason, even after rebuilding the menu by visiting civicrm/menu/rebuild&amp;reset=1 

I don't understand why this worked, but I did the following: 


Go to "Admin" > "Customize Data and Screens" > "Navigation Menu"
Expand the Mailings item and you should see "New A/B test" and "Manage A/B tests" at the bottom. 
For each of these two items, take the following steps: 


Right click on the menu item and choose "Edit" 
Change the # character in the URL field to something else like foo. 
Save. Then edit again, and change back to #