    @Test
    public void addProduct_Should_UpdateStoreAfterOperation() {

        CartProduct product = CartProductFactory.newCartProduct(ProductFakeCreator.createProduct(), 1);
        when(cartDataSource.addProduct(any(CartProduct.class))).thenReturn(Single.just(Cart.EMPTY));

        cartService.addProduct(product)
                .test()
                .assertComplete();

        verify(cartDataSource).addProduct(product);
        verifyCartPublished();
        verifyNoMoreInteractions(cartDataSource);
    }