on Windows you could use something like this in a cmd
echo "A123456789" > dummy.txt
for /L %i in (1,1,26) do type dummy.txt >> dummy.txthowever, the disadvantage of such ASCII only files is that for example that bit7 of neither cell will be written to 1 and even if the bit7 of all cells couldn't hold a 1 you will not be able to find a damaged cell. Therefore I would just simply use a random binary file and do a write and readback test.