  The generation of random numbers is a task of paramount importance in modern
science. A central problem for both classical and quantum randomness generation
is to estimate the entropy of the data generated by a given device. Here we
present a protocol for self-testing quantum random number generation, in which
the user can monitor the entropy in real-time. Based on a few general
assumptions, our protocol guarantees continuous generation of high quality
randomness, without the need for a detailed characterization of the devices.
Using a fully optical setup, we implement our protocol and illustrate its
self-testing capacity. Our work thus provides a practical approach to quantum
randomness generation in a scenario of trusted but error-prone devices.
