Solution of Box, AvgMPFA, NLTPFA, and NLMPFA schemes (first row); solution of MPFA-O, TPFA, MFD, and HFV schemes (second row) for the second discrete extremum principle test case. The solutions are depicted as a surface plot. The tensor used for this test case is specified in (53) with α = 67.5°. On the whole boundary Neumann no-flow conditions are set, whereby two wells are located within the domain where the values of u are fixed. The range of the different solutions is depicted below the different drawings.