Deploying IaC Without Tests? A Four-Layer Validation Pipeline That Cuts 3AM Alerts by 80%
Overview I took over a project last year where a former colleague’s Terraform code was running fine. One Monday morning, he changed a single line of instance_type. terraform plan looked clean. apply succeeded. Then the system blew up. The problem wasn’t a syntax error — the instance_type referenced an AMI that didn’t exist in the target availability zone. plan passed because it only checks “is this logically valid,” not “does this resource actually exist on the cloud....