Attach the lens to your 7D. Set the 7D up on a tripod. Light the test area well. Use the 7D's Live View with x10 magnification to manually focus the lens. Once you do that, take the picture (or even better, activate the shutter remotely using a wireless remote or a corded one). Then analyze your results.

Without doing the steps above, you are more or less testing focus accuracy more than lens sharpness. Isolate the variables.