write a python3 test generator that generates the following tests:
n
s_1s_2s_3...s_n

here s_1s_2s_3...s_n is a string of n characters, each of which is 0 or 1

the testgen is called with the following function:
python3 testgen.py -n N -s S > file.in

where N is the length of the string and S is the seed
