In an effort to explain outstanding issues such as the rotation curves of galaxies, or the nature of dark matter and dark energy,
there has been considerable activity in the development of alternative theories of gravity. While a number of these theories are
heavily constrained by solar system and binary pulsar tests, there essentially remain an infinite family of possible alternative theories to
General Relativity. The investigation of these theories can proceed in two directions : the first is where one formulates
an alternative theory and then designs a test for that specific theory. The second is where one constructs a generic test of deviations from GR and implies the possible alternative theory. Focusing on the inspiral of supermassive black hole binaries, any deviation from GR will be imprinted in the gravitational wave signature due to a modification of both the phase and frequency evolution of the binary. While solar system and binary pulsar tests are conducted in the weak field regime, a future detector, such as eLISA, will have sufficient accuracy to allow us to constrain non-GR theories in the true strong field regime. In this talk, we discuss the results of a first step towards a generic test of non-GR theories.