* - Will only emit changes of a single type (from a single delegate change set)
 */
public class SummarizingChangeContainer implements ChangeContainer {
    private final List<ChangeContainer> sources;

    public SummarizingChangeContainer(ChangeContainer... sources) {
        this.sources = ImmutableList.copyOf(sources);
    }

    @Override

import spock.lang.Specification

class SummarizingChangeContainerTest extends Specification {

    def state1 = Mock(ChangeContainer)
    def state2 = Mock(ChangeContainer)
    def state = new SummarizingChangeContainer(state1, state2)
    def visitor = new CollectingChangeVisitor()

    def "looks for changes in all delegate change sets"() {
        when:
        state.accept(visitor)

        then:

            remainingPreviouslyProducedOutputs
        );

        // Collect changes that would trigger a rebuild
        ChangeContainer rebuildTriggeringChanges = errorHandling(executable, new SummarizingChangeContainer(
            previousSuccessState,
            implementationChanges,
            inputPropertyChanges,
            inputPropertyValueChanges,
            outputFilePropertyChanges,