A mining engineer is to predict rock mass behavior in the influence zones of stoping or active blocks, especially in the vicinity of structural faults. In this regard, it is hard to overestimate the importance of the exact knowledge on the values and orientation patterns of stresses. For gaining a practical insight into the influence of stresses on the rock mass behavior in the zone of stoping or development heading, it is insufficient to know stress values obtained in analysis or interpretation. The exact stress–strain data measured using special tools immediately in the test zone are necessary in all phases of a mine, starting from its planning, design, construction and operation and finishing with its backfill and closure. Aimed to obtained the most reliable data on the stress–strain behavior of rock mass, Sigra designed the method and tool for the in situ stress testing in boreholes. The method and equipment are named Sigra IST 2D and Sigra IST 3D for 2D and 3D stress testing, respectively. These methods and tools are recommended for obtaining actual data for the stress pattern modeling in a mining area prior to mining start, or for modeling the induced stress field both in underground and surface mining. As mining is advanced, such models should be routinely updated and verified using additional measurements.