The client library the key making the complex things simple

138 Chapter 6 Working Beyond the Boundaries

Figuring this out can be done if you include for each new value the version of the value(s) you are updating.There are ways to make this more robust and more complex. If you have to implement this yourself, it may seem like rocket science and is probably overkill.This is why SimpleDB may not be the best choice for making simple counters.

Designing for Testability

Your SimpleDB applications will always use a SimpleDB client, whether from a third party or of your own creation.A big part of testability in this situation involves writing to an interface and not an implementation.The difficulty in this will depend on the lan-guage and client you use.The basic approach is to create a wrapper class around the client and write your application against the wrapper instead of the client.

ing for responses over the network. It can also support your testing scenarios by storing values in memory between test method calls.

Alternatives to Live Service Calls