what can be in test 2/////

I guess it is an anti-hash string <https://en.wikipedia.org/wiki/Thue%E2%80%93Morse_sequence>

My additive hash with N=10 uint64_t still works, while N=5 does not:

  F(i,N) r[i] += ((a<<40) ^ (b<<20) ^ c) * s[i] % q[i]

a,b,c are letters;
s[i] and q[i] are primes;
F(i,n) is for(int i = 0; i < (n); ++i)