Test theories of special relativity give a mathematical framework for analyzing results of experiments to verify special relativity. An experiment to test the theory of relativity cannot assume the theory is true, and therefore needs some other framework of assumptions that are wider than those of relativity. For example, a test theory may have a different postulate about light concerning one-way speed of light vs. two-way speed of light, it may have a preferred frame of reference, and may violate Lorentz invariance in many different ways. Test theories predicting different experimental results from Einstein's special relativity, are Robertson's test theory (1949), and the Mansouri–Sexl theory (1977) which is equivalent to Robertson's theory.Another, more extensive model is the Standard-Mo