Method for testing a memory device, test unit for testing a memory device and memory device

A method, a memory device and a test unit to test such memory device is provided. The memory device comprises a memory cell array including a multitude of memory cells each having a variable characteristic. The method comprises identifying the characteristic of each memory cell and assigning memory cells of the multitude of memory cells to a weak group in dependence on the identified characteristic. Then the stored information of the memory cells assigned to the weak group is restored in order to modify the characteristics of these memory cells.