We are finding that unit testing is pretty straightforward with Placebo [0] (also Mitch Garnaat!), for which we use a common "boto client getter" library that the unit test framework can hook into to inject Placebo.
The really hard part is integration testing. You can Chaos-Monkey your Lambda functions, but you can't Chaos-Monkey DynamoDB. We're looking at ways of building tooling to do that.
For deployment, we wanted to use Serverless, but as they started to move away from CloudFormation, that didn't work for our more enterprise needs, so we've been rolling our own, based on ideas from Kappa.