The problem is that you are listing the variable names in the connect statement.

connect(selectionModel(), SIGNAL(selectionChanged(const QItemSelection &selected, const QItemSelection &deselected)), this, SLOT(testSlot(const QItemSelection &selected, const QItemSelection &deselected)));


should be

connect(selectionModel(), SIGNAL(selectionChanged(const QItemSelection &, const QItemSelection &)), this, SLOT(testSlot(const QItemSelection &, const QItemSelection &)));