### Question:
ActionCollection { public void add(Action action) { if (action == null) { throw new IllegalArgumentException("Action == null"); } _actionColl.put(action.getClass().getName(), action); } ActionCollection(IApplication app); void add(Action action); synchronized Action get(Class<? extends Action> actionClass); synchronized Action get(String actionClassName); @SuppressWarnings("unchecked") void enableAction(Class actionClass, boolean enable); void internalFrameOpenedOrClosed(int nbrInternalFramesOpen); void deactivationChanged(IWidget frame); synchronized void activationChanged(IWidget frame); synchronized void loadActionKeys(ActionKeys[] actionKeys); Iterator<Action> actions(); synchronized void setCurrentSession(ISession session);  }### Answer:
@Test (expected = IllegalArgumentException.class ) public final void testAddNull() { actionCollectionUnderTest.add(null); }