[Hikikomori]

With AWS SAM you can invoke functions locally, run api gateway and use step functions. There's also a 3rd party project to run various AWS services locally, can't remember the project name.

There's also SAM sync that syncs changes you make quickly, so if you have your own dev copy in AWS you can quickly test changes.

[tyingq]

There's also a fair amount of lambdas where you can just invoke the lambda handler yourself without anything special other than a compatible version of python/node/etc. Variations of things like:

node -e "console.log(require('./index').handler(require('./event.json')));"