FolderMock mod1 = new FolderMock("mod1");
FileMock initFromMod1 = new FileMock("__init__.py"); //visited
mod1.addMember(initFromMod1);
mod1.addMember(new FileMock("a.py")); //visited
mod1.addMember(new FileMock("unrelated"));
FolderMock mod2 = new FolderMock("mod2");
mod1.addMember(mod2);
mod2.addMember(new FileMock("__init__.py")); // visited