A quantum channel (a completely positive, trace-preserving map) can be used to send (quantum) information from one location to another. Suppose you have access to a quantum channel but do not know whether that channel is N_1 or N_2. By using the channel n times, you seek to determine which channel is in your possession. What is the optimal rate at which one can correctly answer that N_1 was used while still keeping low the probability of incorrectly answering N_1 when N_2 was used? Using the completely bounded norms of maps between Schatten p-classes and the sandwiched Renyi relative entropy, we recover the same results as in classical hypothesis testing in the case that one of the channels is a replacer channel. No prior knowledge of quantum information theory will be assumed. Based on joint work with Mark M. Wilde and Milan Mosonyi, arXiv:1408.3373.