  Canonically, `classic' tests of general relativity (GR) include perihelion
precession, the bending of light around stars, and gravitational redshift;
`modern' tests have to do with, inter alia, relativistic time delay,
equivalence principle tests, gravitational lensing, strong field gravity, and
gravitational waves. The orthodoxy is that both classic and modern tests of GR
afford experimental confirmation of that theory in particular. In this article,
we question this orthodoxy, by showing there are classes of both relativistic
theories (with spatiotemporal geometrical properties different from those of
GR) and non-relativistic theories (in which the lightcones of a relativistic
spacetime are `widened') which would also pass such tests. Thus, (a) issues of
underdetermination in the context of GR loom much larger than one might have
thought, and (b) given this, one has to think more carefully about what exactly
such tests in fact are testing.
