Test is to take some pictures of an object and see if it is in focus. Try to use something that has a surface that is perpendicular to the camera, also try something with contrast. If you are consistantly seeing in focus behind or infront then you may have to adjust. Some lenses are inconsistant, it depends also on the aperture, the camera will have more trouble focusing at very wide apertures are the DoF is very thin and confuses the camera