private final RuntimeException failure;

    public AbstractFailure(RuntimeException failure) {
        this.failure = failure;
    }

    @Override
    public boolean isFailure() {
        return true;
    }

    @Override
    public RuntimeException getFailure() {
        return failure;
    }

    @Override
    public void writeTo(int requestId, HttpExchange exchange) {

 */

package org.gradle.test.fixtures.server.http;

import com.sun.net.httpserver.HttpExchange;

import java.io.IOException;

interface ResponseProducer {
    default boolean isFailure() {
        return false;
    }

    /**
     * Called to handle a request. Is *not* called under lock.
     */
    void writeTo(int requestId, HttpExchange exchange) throws IOException;

    /**

     */
    public abstract ExecutionResult<T> withFailures(ExecutionResult<Void> otherResult);

    /**
     * Casts a failed result.
     */
    public abstract <S> ExecutionResult<S> asFailure();

    public static <T> ExecutionResult<T> succeeded(T value) {
        return new Success<T>() {
            @Override
            public T getValue() {
                return value;
            }
        };

        result.failures.empty
        result.rethrow()

        when:
        result.failure

        then:
        thrown(IllegalArgumentException)

        when:
        result.asFailure()

        then:
        thrown(IllegalArgumentException)
    }

    def "can query successful void result"() {
        def result = ExecutionResult.succeeded()

        expect:

                ExecutionResult<Void> result = workController.scheduleAndRunRequestedTasks(null);
                if (!result.getFailures().isEmpty()) {
                    return result.asFailure();
                }
            }
            T model = modelCreator.fromBuildModel(action);
            return ExecutionResult.succeeded(model);
        });
    }

    @Override