Integration testing of Terraform modules

In one of the previous chapters on making various tools play well with Terraform, we already took a quick look at running infrastructure tests. Back then we used Inspec to run a test against the single EC2 instance. A few chapters forward, and now we have much more complex Terraform setup on our hands, one that is split across four repositories.

If we would consider ourselves old-fashioned traditional system administrators, we would be quite happy with what we have achieved by now. But a good software developer (and if we are doing Infrastructure as Code, then we are already software developers, regardless of our previous experience) would never leave any code without proper tests. And what we wrote in the past is nothing like a proper test.

But what should we test? We must not run tests against the production environment (the one we just configured GitLab CI for), and it is meaningless to test VPC and IAM repositories in isolation. So the only good...