List<Object> factoryArgs = argGroups.get(item.groupNumber).get(item.itemNumber);
              return factory.getName()
                  + "("
                  + Joiner.on(", ").useForNull("null").join(factoryArgs)
                  + ")";
            });
    tester.addEqualityGroup(instance, createInstance(factory, equalArgs));
    for (int i = 0; i < params.size(); i++) {