A method and apparatus for testing random numbers generated by a random-number generator in real time. A stream of random bits generated by the random-number generator is segmented into a predefined block of bits, then these blocks undergo a gap-length-calculation operation in which it is determined for which specific range the gap belongs to, then these gap length values are applied to an exponential-counting operation to obtain and update gap-frequency values for different bit patterns and gap ranges. Thereafter, the updated gap-frequency values are compared to at least one predetermined acceptance range, so that if at least one of the gap-frequency values falls repeatedly outside the predetermined acceptance range more than a predetermined number of times, it is determined that the generated random bits are insufficiently random.