String propertyName = "property";
underTest.setResolver(slot, new CalculationResolver(propertyName,
new SumCalculation()));
Resource resource1 = createResource(TYPE_1, 1);
resource1.putValue(propertyName, 1d);
helper.addToContainedResources(resource1);
final VisualItem visualItem = underTest.getFullVisualItemContainer()
.getVisualItems().getFirstElement();
visualItem.getValue(slot); // caches values
// needs to be done before adding
final double[] result = captureVisualItemNumberSlotValueOnUpdate(visualItem);
Resource resource2 = createResource(TYPE_1, 2);
resource2.putValue(propertyName, 2d);
helper.addToContainedResources(resource2);
assertEquals(1d + 2d, result[0], 0.000001d);
}