  Measurements of the interaction rates of the solar neutrino lines of $^7$Be
and $pep$ can be used, independent of solar models, to test whether electron
flavor is conserved, to determine survival probabilities of electron-type
neutrinos at specific energies, and to test for the existence of sterile
neutrinos. We present analytic descriptions of these tests. We also illustrate
by numerical simulations, assuming matter-enhanced and vacuum neutrino
oscillations, what measurements of solar neutrino lines can teach us about
neutrino masses and mixing angles.
