docker-lambda | Docker images and test runners | Continuous Deployment library

When you want fast local reproducibility. When you don't want to spin up an Amazon Linux EC2 instance (indeed, network aside, this is closer to the real Lambda environment because there are a number of different files, permissions and libraries on a default Amazon Linux instance). When you don't want to invoke a live Lambda just to test your Lambda package – you can do it locally from your dev machine or run tests on your CI system (assuming it has Docker support!). By tarring the full filesystem in Lambda, uploading that to S3, and then piping into Docker to create a new image from scratch – then creating mock modules that will be required/included in place of the actual native modules that communicate with the real Lambda coordinating services. Only the native modules are mocked out – the actual parent JS/PY/Java runner files are left alone, so their behaviors don't need to be replicated (like the overriding of console.log, and custom defined properties like callbackWaitsForEmptyEventLoop).