In experimental physics, a test theory tells experimenters how to perform particular comparisons between specific theories, or between specific classes of theory.

Without a good reference test theory, these experiments can be difficult to construct: different theories often define relationships and parameters in different (often incompatible) ways, and sometimes physical theories and models that nominally produce significantly diverging predictions can be found to produce very similar (or even identical) predictions, once definitional differences are taken into account.

A good test theory should identify potential sources of definitional bias in the way that experiments are constructed, and should ideally be able to deal with a wide range of possible objections to experimental tests based upon it - if a popular test theory does turn out to contain serious omissions, this can undermine the validity of subsequent experimental work.

This physics-related article is a stub. You can help Wikipedia by expanding it.