You can definitely emulate parts of this. For example LocalStack can spawn ECS tasks using Docker, or EC2 VMs using something like VirtualBox. Load balancers are also emulated, so you can test load balancing configurations with IP address or Lambda targets. LocalStack is currently not emulating all of the VPC network configuration, so although you can make the API calls to create VPCs subnet groups and so on, LocalStack currently wouldn't enforce these on a network level.
Thanks for the detailed reply. Would I be able to take most, if not all, of my existing Terraform code and use it to stand up my topology in LocalStack? If so, that would be quite useful.
