What is LocalStack?
LocalStack provides an easy-to-use test/mocking framework for developing Cloud applications. It spins up a testing environment on your local machine that provides the same functionality and APIs as the real AWS cloud environment.
You can run your Lambda functions, store data to DynamoDB tables, feed events through Kinesis streams, put your application behind an API Gateway, and much more. And all this happens on your local machine, without ever talking to the cloud.