Ask HN: What Is a Good Toolset for Serveless Development?

We use AWS Lambda quite a lot in our tooling for various things and whilst I can definitely see that it solves a few problems associated with the traditional 'server hosted code' (infinite scaling / portability etc) I have never found developing the lambda functions particularly fun.

We currently use Cloud9 as it seems to have a decent deployment capability built into it for Lambda, however I am aware that this isn't exactly portable and I have found that the response is different when deployed via AWS API Gateway than through the in built testing tools.

What development environments are people using to develop larger serverless deployments? Is everyone using serverless.com/framework/? Is there something better?