Try rebooting your device.
I had the same problem using Xcode 4.5.1 and iPad 6.0.1, but at that time I didn’t want to update. In addition to the long “Test Application” step, I noticed that copying resources was even slower. After that, I turned off the iPad and tried to uninstall my application, but found that even the device to remove the alerts took a few moments. Therefore, obviously, for me it was a problem with the device, and after shutting down / restarting the device, xcode ran to previously normal speeds.
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