How to test a random generator

Question

I need to test a random number generator which produces numbers randomly. How to make sure the numbers generated are random.

Answer 1

It's a very difficult thing.

You may try ENT from Fourmilab and compare it with the results against their RNG, HotBits. You may also like to review Random.org.

This also looks interesting: Diehard tests (I've not worked with it though).