Mock AWS SQS implementation which operatesin-memory rather than hitting the real SQS.

MockSQS.java

import com.amazonaws.AmazonClientException;
import com.amazonaws.AmazonServiceException;
import com.amazonaws.AmazonWebServiceRequest;
import com.amazonaws.ResponseMetadata;
import com.amazonaws.regions.Region;
import com.amazonaws.services.sqs.AmazonSQS;
import com.amazonaws.services.sqs.model.*;
import com.google.common.hash.Hashing;

import java.util.*;
import java.util.concurrent.*;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Sitting in the airport, unable to connect to the internet, this seemed
 * like a good use of my time, at least as compared with sleeping.
 *
 * @author Ben Fagin
 * @version 2013-05-28
 */
public class MockSQS implements AmazonSQS {
	private final Map<String, Queue<MessageInfo>> queues = new HashMap<>();
	private final ScheduledExecutorService executor = Executors.newScheduledThreadPool(10);
	private int timeout = 35*60;
	private final Map<String, ScheduledMessage> receivedMessages = new HashMap<>();

	/*
		- adds a message to the correct queue
		- delays if required
	 */
	@Override
	public SendMessageResult sendMessage(final SendMessageRequest request) throws AmazonServiceException, AmazonClientException {
		final Queue<MessageInfo> queue = getOrCreateQueue(request.getQueueUrl());
		final MessageInfo info = new MessageInfo();
		info.body = checkNotNull(request.getMessageBody());
		info.id = UUID.randomUUID().toString();

		if (request.getDelaySeconds() == null) {
			queue.add(info);
		} else {
			Runnable task = new Runnable() {
				public void run() {
					queue.add(info);
				}
			};
			executor.schedule(task, request.getDelaySeconds(), TimeUnit.SECONDS);
		}

		return new SendMessageResult().withMessageId(info.id).withMD5OfMessageBody(info.hash());
	}

	/*
		- takes messages off the queue
		- if timeout, then they are added back
	 */
	@Override
	public ReceiveMessageResult receiveMessage(ReceiveMessageRequest request) throws AmazonServiceException, AmazonClientException {
		final Queue<MessageInfo> queue = getOrCreateQueue(request.getQueueUrl());
		List<Message> messages = new ArrayList<>();

		Integer max = request.getMaxNumberOfMessages();
		if (max == null) { max = 0; }
		checkArgument(max <= 10 && max > 0);

		Integer visibilityTimeout = request.getVisibilityTimeout();
		if (visibilityTimeout == null) { visibilityTimeout = timeout; }

		for (int i=0; i < max; ++i) {
			final MessageInfo info = queue.poll();

			if (info != null) {
				final String receiptHandle = UUID.randomUUID().toString();

				Message message = new Message();
				message.setBody(info.body);
				message.setMessageId(info.id);
				message.setMD5OfBody(info.hash());
				message.setReceiptHandle(receiptHandle);
				messages.add(message);

				Runnable command = new Runnable() {
					public void run() {
						queue.add(info);
						receivedMessages.remove(receiptHandle);
					}
				};

				ScheduledMessage scheduled = new ScheduledMessage();
				scheduled.future = executor.schedule(command, visibilityTimeout, TimeUnit.SECONDS);
				scheduled.runnable = command;
				receivedMessages.put(message.getReceiptHandle(), scheduled);
			}
		}

		return new ReceiveMessageResult().withMessages(messages);
	}

	/*
		- deletes the task which would have re-added a message to the queue,
		  effectively deleting the message
	 */
	@Override
	public void deleteMessage(DeleteMessageRequest request) throws AmazonServiceException, AmazonClientException {
		ScheduledMessage scheduled = receivedMessages.remove(request.getReceiptHandle());
		if (scheduled == null) {
			throw new RuntimeException("message does not exist");
		}

		scheduled.future.cancel(true);
	}

	@Override
	public void changeMessageVisibility(ChangeMessageVisibilityRequest request) throws AmazonServiceException, AmazonClientException {
		ScheduledMessage scheduled = receivedMessages.get(request.getReceiptHandle());
		if (scheduled == null) {
			throw new RuntimeException("message does not exist");
		}

		scheduled.future.cancel(true);
		scheduled.future = executor.schedule(scheduled.runnable, checkNotNull(request.getVisibilityTimeout()), TimeUnit.SECONDS);
	}

	@Override
	public void shutdown() {
		executor.shutdown();
		receivedMessages.clear();
		queues.clear();
	}

	private static class MessageInfo {
		String body;
		String id;

		String hash() {
			return Hashing.md5().hashString(body).toString();
		}
	}

	private static class ScheduledMessage {
		ScheduledFuture future;
		Runnable runnable;
	}

	private Queue<MessageInfo> getOrCreateQueue(String url) {
		Queue<MessageInfo> queue = queues.get(checkNotNull(url));

		if (queue == null) {
			synchronized (queues) {
				queue = queues.get(checkNotNull(url));

				if (queue == null) {
					queue = new ArrayDeque<>();
					queues.put(url, queue);
				}
			}
		}

		return queue;
	}

	/*
		- set the default timeout when receiving messages from the queue
	 */
	public void setTimeout(int timeout) {
		this.timeout = timeout;
	}

	//---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---o---//

	@Override
	public void setEndpoint(String endpoint) throws IllegalArgumentException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public void setRegion(Region region) throws IllegalArgumentException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public void setQueueAttributes(SetQueueAttributesRequest setQueueAttributesRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public ChangeMessageVisibilityBatchResult changeMessageVisibilityBatch(ChangeMessageVisibilityBatchRequest changeMessageVisibilityBatchRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public GetQueueUrlResult getQueueUrl(GetQueueUrlRequest getQueueUrlRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public void removePermission(RemovePermissionRequest removePermissionRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public GetQueueAttributesResult getQueueAttributes(GetQueueAttributesRequest getQueueAttributesRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public SendMessageBatchResult sendMessageBatch(SendMessageBatchRequest sendMessageBatchRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public void deleteQueue(DeleteQueueRequest deleteQueueRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public ListQueuesResult listQueues(ListQueuesRequest listQueuesRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public DeleteMessageBatchResult deleteMessageBatch(DeleteMessageBatchRequest deleteMessageBatchRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public CreateQueueResult createQueue(CreateQueueRequest createQueueRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public void addPermission(AddPermissionRequest addPermissionRequest) throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public ListQueuesResult listQueues() throws AmazonServiceException, AmazonClientException {
		throw new RuntimeException("not implemented");
	}

	@Override
	public ResponseMetadata getCachedResponseMetadata(AmazonWebServiceRequest request) {
		throw new RuntimeException("not implemented");
	}
}

Hi!

Just wanted to say THANK YOU VERY MUCH for this one. It really helps us big time. I created our own implementation https://gist.github.com/orvyl/870fba7ddbaeeb6ad651930a1c3c98aa because we are now using Java8 and aws-java-sdk v1.11.86 and it was 100% based into this one. Again, thank you!