<human>:  With regards to superconductivity and Josephson junctions, how do you know that a superconductor is superconducting?
<bot>: You can test for superconductivity using a Josephson junction. A Josephson junction is a device that allows current to flow across two superconductors separated by a thin insulator. In the case of a superconductor, the insulator will allow current to flow through it without resistance, but in the case of a normal conductor, the insulator will act as a barrier that prevents current from flowing.