In many functor calculus settings, it is useful to obtain model structures with specified fibrant objects using the $Q$-localization of Bousfield and Friedlander. The notion of a tested $Q$-localization is an upgraded version of this localization so that the resulting model category is cofibrantly generated. It is not hard to show that tested $Q$-localizations of proper model categories can also be viewed as left Bousfield localizations, but the converse direction is more subtle. In joint work with Griffiths, Johnson, Santhanam, and Taggart, we consider this interplay of localizations for several different kinds of functor calculus, as well as for familiar left Bousfield localizations.