void () { VirtualFile first = tempDirectory.newVirtualDirectory("first/"); VirtualFile second = tempDirectory.newVirtualDirectory("second/"); assertNothingToRescan(); libraryRootsNoId.add(first); assertRescanningLibraries(YES, first); assertNothingToRescan(); libraryRootsNoId.add(second); assertRescanningLibraries(YES, second); assertNothingToRescan(); libraryRootsNoId.remove(second); assertNothingToRescan(); }