A pressure testing system for analyzing a rock formation includes a tubular support member sized to pass into a wellbore of the rock formation and an adjustable loading device configured to exert a radial load against the wall of the wellbore. The adjustable loading device includes multiple expandable members distributed around a circumference of the tubular support member and configured to expand to respectively exert multiple radial pressures against the wall of the wellbore that together provide the radial load. The pressure testing system further includes a control module configured to selectively control expansion of each expandable member of the multiple expandable members to vary the radial load exerted by the adjustable loading device as a function of an angle around the circumference of the tubular support member.