Implementing a Cycle ResponseHandler in Moco for Repeating Requests

When using the Moco testing framework, the official documentation mentions a cycle() method for returning an array of responses in a loop, but the method is not present in the public API. To fill this gap, a custom CycleHandle class is implemented by extending AbstractResponseHandler.

package com.fun.moco.support;

import com.github.dreamhead.moco.MocoConfig;
import com.github.dreamhead.moco.ResponseHandler;
import com.github.dreamhead.moco.handler.AbstractResponseHandler;
import com.github.dreamhead.moco.internal.SessionContext;
import com.google.common.base.Function;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.FluentIterable.from;
import static com.google.common.collect.ImmutableList.copyOf;

/**
 * Cycle response handler that returns responses in a round‑robin fashion.
 */
@SuppressWarnings("all")
public class CycleHandle extends AbstractResponseHandler {
    private final ImmutableList<ResponseHandler> handlers;
    private int index;

    private CycleHandle(final Iterable<ResponseHandler> handlers) {
        this.handlers = copyOf(handlers);
    }

    public static ResponseHandler newSeq(final Iterable<ResponseHandler> handlers) {
        checkArgument(Iterables.size(handlers) > 0, "Sequence contents should not be null");
        return new CycleHandle(handlers);
    }

    @Override
    public void writeToResponse(final SessionContext context) {
        handlers.get((index++) % handlers.size()).writeToResponse(context);
    }

    @Override
    public ResponseHandler apply(final MocoConfig config) {
        if (config.isFor(MocoConfig.RESPONSE_ID)) {
            return super.apply(config);
        }
        FluentIterable<ResponseHandler> transformedResources = from(copyOf(handlers)).transform(applyConfig(config));
        return new CycleHandle(transformedResources.toList());
    }

    private Function<ResponseHandler, ResponseHandler> applyConfig(final MocoConfig config) {
        return new Function<ResponseHandler, ResponseHandler>() {
            @Override
            public ResponseHandler apply(final ResponseHandler input) {
                return input.apply(config);
            }
        };
    }
}

Two convenience static methods are provided for Groovy (and can be converted to Java) to create a cyclic response handler from either raw strings or existing ResponseHandler instances.

/**
 * Cycle return for string contents.
 */
static ResponseHandler cycle(String content, String... contents) {
    return CycleHandle.newSeq(
        FluentIterable.from(asIterable(content, contents)).transform(textToResource())
    );
}

/**
 * Cycle return for existing handlers.
 */
static ResponseHandler cycle(final ResponseHandler handler, final ResponseHandler... handlers) {
    return CycleHandle.newSeq(asIterable(handler, handlers));
}

These utilities allow developers to define a sequence of responses that Moco will serve repeatedly, which is useful for testing scenarios that involve multiple request attempts such as order submissions, resource deletions, or retry logic.