Terraform Quickstart: Part 10 – Terraform Testing Guide

How to Write and Run Terraform Tests to Avoid Downtime and Bugs

Introduction

A team rolls out a new Terraform change to production. They accidentally referenced the wrong security group ID, resulting in critical services going offline. Downtime could have been avoided with a simple test.

Just like any application code, your Terraform configurations need testing. It helps catch errors early and improve the stability of your code.

Some frequent errors include:

• Using the wrong resource types or values.

• Breaking changes in modules.

• Security misconfigurations.

• Missing dependencies between resources.

📚Do you want to read all lessons in a single pdf? Check out my Terraform Quickstart ebook.

In this chapter, you’ll learn:

• Types of tests used in Terraform projects.

• Common mistakes tests can catch.

• Tools you can use to test Terraform code.

Types of Terraform Tests

Tests help you validate changes before deployment, especially in CI/CD pipelines. Refer to this testing pyramid:

Let’s explore the stages one by one:

1. Terraform Validate and Format

It checks if your config is syntactically correct and all required variables are defined.

$ terraform validate

Use this before every plan.

This ensures your files follow consistent formatting.

$ terraform fmt -check

It also avoids noisy diffs in version control.

2. Static Analysis

For example, tfsec is a 3rd party tool that detects issues like open security groups, public S3 buckets, missing encryption.

$ tfsec .

Checkov is another security scanner:

$ checkov -d .

It supports many cloud providers and has extensive policies.

3. Unit & Integration Testing with Terratest (Go)

Terratest is a Go framework for testing Terraform code. You can write tests like:

terraformOptions := &terraform.Options{
    TerraformDir: "../modules/my-vpc",
}

terraform.InitAndApply(t, terraformOptions)

This approach:

• Deploys real infrastructure

• Verifies with assertions (e.g. "Is the VPC created?")

• Destroys after test run

It's powerful but requires Go and more setup.