Extend the target classes to other project trees

[Cael35]

We mutate only classes included in modules of the current tree, if parent project is located in another tree, classes of packages located in other trees are not mutated.
The whole project graph should be browsed to build target modules list (complete the PmpContext.getProjectModules method).

[nrainer]

What does this exactly mean? Can tests reach classes in modules of other trees?
Do you have an example for this? Thanks :)