A method for forming lateral boreholes from an existing parent wellbore is provided. The wellbore has been completed with a string of production casing. The method generally comprises providing a downhole tool assembly having a whipstock. The method also includes running the assembly down into the parent wellbore. A force is applied to the assembly to cause the whipstock to rotate within the wellbore into an operating position. In this position, a curved face of the whipstock forms a bend-radius substantially across the inner diameter of the casing. A jetting hose is run into the wellbore. Upon contact with the curved face of the whipstock, the jetting hose is re-directed through a window in the production casing. Hydraulic fluid is injected under pressure through the hose to provide hydraulic jetting. The hose is directed through the window and into the formation to create a lateral borehole extending many feet outwardly into a subsurface formation. A method of testing a subsurface formation for the presence of hydrocarbon fluids is also provided herein.