Non-signaling strategies are a generalization of quantum strategies that have been studied in physics for decades, and have recently found applications in theoretical computer science. These applications motivate the study of local-to-global phenomena for non-signaling functions.

We present general results about the local testability of linear codes in the non-signaling setting. Our contributions include formulating natural definitions that capture the condition that a non-signaling function "belongs" to a given code, and characterizing the sets of local constraints that imply membership in the code. We prove these results by relating the Fourier spectrum of non-signaling functions to Cayley hypergraphs induced by local constraints.

We apply the above results to show a separation between locally testable codes in the classical and non-signaling setting by proving that bivariate low-degree testing fails spectacularly in the non-signaling setting. Specifically, we show that there exist non-signaling functions that pass bivariate low-degree tests with probability 1, and yet are maximally far from low-degree.