@SuppressWarnings("ConstantConditions")
    public void addAction(@NonNull Action a) {
        if (a == null) {
            throw new IllegalArgumentException("Action must be non-null");
        }
        getActions().add(a);
    }
@SuppressWarnings("deprecation")
    @Test
    public void addAction() {
        CauseAction a1 = new CauseAction();
        ParametersAction a2 = new ParametersAction();
        assertEquals(Collections.<Action>emptyList(), thing.getActions());
        thing.addAction(a1);
        assertEquals(List.of(a1), thing.getActions());
        thing.addAction(a2);
        assertEquals(Arrays.asList(a1, a2), thing.getActions());
    }