Before we resort to the dreaded `/* used for testing */` comment I think there are a few other tactics we can try here. For example:

* Passing a `Router` into `RouteFragment.newInstance(...)`
* Creating a `RouteFragment#getRouter()` instance method with protected scope that can be overridden in tests.
* Dependency injection (Dagger?)

This article gives a nice example of the various approaches.

http://monkeyisland.pl/2009/01/13/subclass-and-override-vs-partial-mocking-vs-refactoring/