Self-testing quantum random number generators have a unique place in quantum technologies, since they allow for the monitoring of the source’s entropy in real time by measuring the input-output statistics. Our device uses a prepare-and-measure protocol where two states are prepared, a coherent state or the vacuum, and then a detector performs unambiguous state exclusion to discriminate between them. The protocol is semi-device independent, while the randomness is certified only with an assumption on the overlap of the two prepared states. The QRNG is also self-testing, meaning that we can monitor the correct function of the setup in real-time. This implementation is a prototype, implemented in a box using off-the-shelf commercial components. With our simple setup we achieved real-time extraction of truly random numbers with a rate of 6.8 MHz.