Testing Infrastructure as Code: Ensuring Your Automation is Safe

If Infrastructure as Code (IaC) is code, it should be tested like code. Yet, many organizations still "deploy and pray" when it comes to their infrastructure updates. A robust IaC testing strategy reduces the risk of misconfigurations and production outages.

The IaC Testing Pyramid

1. Static Analysis (Linting): Check for syntax errors and style consistency (e.g., tflint).
2. Security Scanning: Scan for common misconfigurations and security vulnerabilities (e.g., tfsec, checkov).
3. Unit Testing: Test small parts of your code in isolation (e.g., using terraform test or Terratest).
4. Integration Testing: Deploy your code to a sandbox environment and verify that the resources are created correctly and are functional.
5. Policy Checking: Ensure your code complies with organizational rules (e.g., OPA, Sentinel).

Why it's hard

Infrastructure tests are often slow (waiting for cloud resources to be created) and expensive. The key is to run fast, static tests on every commit, and reserve slow, integration tests for major changes or pull requests.

A pragmatic CI pipeline

• on every PR: format + lint + security scan + policy checks
• for risky changes: deploy to a sandbox account and run integration tests
• before prod: require an approval with the plan output attached

Common anti-patterns

• running apply without reviewable plans
• long-lived credentials in CI instead of short-lived identity (OIDC)
• treating warnings as “noise” until an incident happens

Conclusion

Testing IaC is an investment in stability. By catching errors early in the development cycle, you reduce the cost of fixes and increase the confidence of your engineering teams in their automated delivery flows.