How to Test Terraform Infrastructure Code

Terraform code needs to be tested to ensure that it works as expected. In this post, we'll look at some best practices for testing Terraform infrastructure code.
February 14, 2023
min read
Yehonatan Rumyantsev
Cloud Specialist
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TL;DR

Terraform is an open-source infrastructure as code tool that provides a way to manage and provision infrastructure resources. It has become a popular tool among DevOps teams as it allows them to write code that can create and manage infrastructure in a consistent and repeatable manner.

But like any other code, Terraform code needs to be tested to ensure that it works as expected. In this blog post, we'll look at some best practices for testing Terraform infrastructure code.

1. Use Terraform's Built-in Testing Features

Terraform comes with built-in testing features that allow you to validate your infrastructure code. These include:

  • terraform validate command: This command checks the syntax of your code and ensures that all required values are provided.
  • terraform plan command: This command generates an execution plan that shows what changes will be made to your infrastructure. You can use this to verify that the changes are what you intended.
  • terraform apply command: This command applies the changes to your infrastructure. It's a good idea to run this in a test environment before deploying to production.

Using these built-in features is a good starting point for testing your infrastructure code.

2. Use Automated Testing Tools

You can also use automated testing tools to test your Terraform code. Some popular options include:

  • Terratest: A testing framework that provides helpers and abstractions for testing Terraform code.
  • Kitchen-Terraform: A tool that uses Test Kitchen to test Terraform code.
  • tfRails : A tool that allows full blown testing beyond Unit tests.

Using these tools can help you catch issues before they make it to production.

3. Use Version Control

Version control is essential for any codebase, including Terraform code. By using version control, you can track changes to your code and easily revert to a previous version if something goes wrong.

Git is a popular version control system that works well with Terraform code. You can use Git to create branches for different features, test changes in isolation, and merge changes back into the main branch when they're ready.

4. Test in a Sandbox Environment

It's important to test your Terraform code in an environment that's as close to production as possible. However, testing in a production environment is not always feasible or desirable.

Instead, you can create a sandbox environment that mimics your production environment as closely as possible. This could be a separate AWS account or a virtual machine running locally.

By testing in a sandbox environment, you can catch issues before they affect production, and you can also test changes to your infrastructure without impacting production users.

Or

You can use tfRails which is able to mimic your production environment before deployment.

5. Use Continuous Integration and Deployment

Continuous integration and deployment (CI/CD) is a set of practices that automates the building, testing, and deployment of code. By using CI/CD, you can ensure that your Terraform code is tested and deployed automatically.

There are many tools available for CI/CD, including Jenkins, CircleCI, and TravisCI. By using a CI/CD pipeline, you can ensure that your Terraform code is tested and deployed consistently.

In conclusion, testing Terraform infrastructure code is essential for ensuring that your infrastructure is reliable and predictable. By using the built-in testing features of Terraform, automated testing tools, version control, sandbox environments, and CI/CD, you can catch issues early and deploy changes with confidence.

Unit Testing Terraform

Unit tests are designed to test individual units or components of code in isolation. In Terraform, unit testing can be done using a combination of the built-in testing features and custom test scripts.

To unit test Terraform code, you can follow these steps:

  1. Write a test script that calls the Terraform code and validates the expected output.
  2. Use the terraform validate command to check the syntax of the code and ensure that all required values are provided.
  3. Use the terraform plan command to generate an execution plan and validate that the expected changes are being made.
  4. Use the terraform apply command to apply the changes to the infrastructure and validate that the expected resources are created.

By using these steps, you can create unit tests that validate individual modules or resources in isolation. You can also use custom test scripts to test specific use cases or edge cases.

Integration Testing Terraform

Integration testing is designed to test how different components of a system work together. In Terraform, integration testing can be done by deploying infrastructure resources to a test environment and validating that they work as expected.

To integration test Terraform code, you can follow these steps:

  1. Create a test environment that closely mimics your production environment. This could be a separate AWS account, a virtual machine running locally, or a cloud sandbox environment.
  2. Use a CI/CD pipeline to automatically deploy your Terraform code to the test environment.
  3. Run automated tests to validate that the infrastructure resources are working as expected. This could include running functional tests, load tests, or security tests.
  4. Use the terraform destroy command to tear down the resources after the tests have been completed.

By using these steps, you can create integration tests that validate how different components of your infrastructure work together. You can also use automated testing tools, such as Terratest or Kitchen-Terraform, to automate the deployment and testing of your Terraform code in the test environment.

In conclusion, unit testing and integration testing are both important for ensuring that your Terraform code is reliable and predictable. By using a combination of the built-in testing features, custom test scripts, and automated testing tools, you can catch issues early and deploy changes with confidence.