Q:

Emulating Amazon SQS during development

I'm quite interested in beginning some development using Amazon SQS, perhaps SimpleDB too, my question is this, are there any open source solutions that mimic the functionality, just for the purposes of development.  I've already encountered the Eucalyptus project (http://open.eucalyptus.com) for creating an EC-esque cloud. 
I've not had any success with google, I suspect it's because the cost of entry is so inexpensive, but still, does anyone know of anything like this? 

A:

For SQS I wrote ElasticMQ, which you can run either embedded (it's written in Scala, so runs on the JVM) or stand-alone.  It has both persistent and in-memory modes, the first being good for dev, second for testing. 

A:

Some of the Amazon SDKs have "mock" mode, which is:

The mock service is an alternate way
  to use the sample code.  The service
  doesn't call AWS, but instead returns
  a set response that you can modify to
  suit your needs (the XML response
  files are in the Mock directory).  The
  mock service makes it easy for you to
  test how your application handles
  different responses. 

For SQS, it appears the Perl and PHP SDKs have mock mode.  I know that the .NET SDK for Amazon RDS also has the mock mode. 
The Java SDK doesn't contain mock implementations:

The client mock implementations have been removed.  Instead, developers
  are encouraged to use more flexible and full featured mock libraries,
  such as EasyMock, jMock

If the SDK you will be using doesn't have the mock mode available, you could probably create your own similar type of thing which returns the preconfigured responses instead of actually hitting up the service. 
See here for more info

A:

Regarding the Java SDK, it does no longer contain mock implementations:

The client mock implementations have been removed.  Instead, developers
  are encouraged to use more flexible and full featured mock libraries,
  such as EasyMock, jMock

