The Importance of Testing Infrastructure as Code Before Deployment

When it comes to Infrastructure as Code (IaC) tools like Terraform, Pulumi, and Amazon CDK, deploying infrastructure can be a breeze. You can spin up entire environments with just a few lines of code! However, as with any code, bugs are inevitable. And unlike traditional software development, code that deploys infrastructure can have serious consequences if something goes wrong.

That's where testing infrastructure as code comes in. In this article, we'll explore the importance of testing infrastructure as code before deployment and why it should be an essential part of your infrastructure deployment process.

What is Infrastructure as Code?

Before we dive into the importance of testing infrastructure as code, let's make sure we're all on the same page regarding what IaC is. Simply put, IaC is the practice of managing infrastructure using code. This code can be written in a variety of programming languages, but the goal is always the same: define the desired infrastructure state in code and use an IaC tool to make it happen.

The main benefits of IaC are that it makes infrastructure deployments more consistent, repeatable, and trackable. Developers can define their infrastructure needs in code, version control it, and share it with others. And because the infrastructure code is just code, developers can use the same tools they are familiar with, such as version control systems and continuous integration (CI) pipelines, to manage it.

Why Test Infrastructure as Code?

One of IaC's most significant advantages is its ability to make infrastructure deployments more reliable. By defining infrastructure as code, developers can ensure that the infrastructure is set up correctly every time it is deployed. But just like any code, infrastructure code can have bugs. And when those bugs are deployed, they can cause catastrophic problems.

Not testing infrastructure code before deployment is like testing new software without running any unit tests. You might get lucky and have everything work fine, but more likely, you'll miss critical bugs that will cause problems later. Testing infrastructure code is essential to ensure that the resulting infrastructure is correct, complete, and secure.

What Types of Tests Should You Run on Infrastructure Code?

When it comes to testing infrastructure code, there are several types of tests that you should run:

Syntax and Linting Tests

Before running any other tests, it's essential to ensure that your infrastructure code is syntactically valid and conforms to style guidelines. Syntax and linting tests use tools such as Terraform's validate command or Pulumi's pulumi preview command to check that your code uses valid syntax and follows linter rules.

Syntax and linting tests are the first level of defense against syntax issues, typoed resource names or wrong types. While not providing any coverage on the correctness of your code, they can catch many issues and make apparent any inconsistency in code structure.

Unit Tests

Just like with software development, unit tests verify that individual components of the infrastructure code work as expected. In the case of infrastructure code, this typically means testing individual resources or modules independently of the entire stack to ensure that they behave correctly.

Unit tests can cover every single function, and complicated scenarios with many combinations of inputs, backing up your code against minor issues that when combined may turn into major issues. Terratest is a common tool to write infrastructure tests in Golang.

Unit tests can catch subtle bugs that might not show up in higher-level tests. Writing validation tests to check particular properties of resources might help you identify infrastructure issues early.

Integration Tests

While unit tests verify the individual components' behavior, integration tests test how those components function when deployed together. These tests involve spinning up an environment similar to what the production environment will look like, deploying the code, and testing the components’ interaction. This type of test can run in a more controlled environment, simulating some failure scenarios, and allowing for more complete validations.

Integration tests are the last line of defense against critical issues that can arise when deploying all components or inter-components of a system.

Acceptance Tests

Acceptance tests verify that the infrastructure works as intended and their features properly received by users. You can also use real-world scenarios or production-like data to test and validate your infrastructure. While similar to integration tests, acceptance tests provide an end-to-end, real-world understanding of the infrastructure's behavior, which could help discover edge cases and potential issues.

It is essential to clarify that while acceptance tests verify how infrastructure will operate under production conditions, they do not constitute a complete production test.

Benefits of Testing Infrastructure as Code

Now that we've covered the types of tests you should run on infrastructure code let's look at the benefits of testing.

Identify Bugs Early

One of the biggest benefits of testing infrastructure code is the ability to identify bugs early. By identifying issues before deployment, you can fix them before they cause problems. Your tests should fail early and conveniently, flagging evident anomalies - failing tests are the signal that your code is off, and you must look for the buggy code.

Ensure Infrastructure Stability

Testing infrastructure code can also ensure that the resulting infrastructure is stable. Infrastructure code that has been thoroughly tested is less likely to cause unexpected issues, and when an issue arises, it can be quickly identified, fixed, and deployed.

Ensure Compliance and Security

Testing infrastructure code can also help ensure compliance and security. By verifying that infrastructure resources are configured correctly, you reduce the risk of misconfiguration and compliance issues. Furthermore, running security tests on your infrastructure code can help identify potential security vulnerabilities before they are exploited.

Reduce Manual Work

Next, testing infrastructure code can reduce manual work. Testing infrastructure code can be automated, freeing up developers' time to focus on more critical tasks.

Improved Collaboration

By writing executable tests, you make the validation process more traceable and ready for discussion. Tests can also be seen as a knowledge repository, as they can show intent and rationale for past decisions when looking at old tests' evidence.

Save Costs in Production

Finally, testing infrastructure code can save costs in production. By catching issues early and addressing them before deployment, you reduce issues in production, which in turn reduces costs.

Conclusion

Testing infrastructure code is a crucial part of any infrastructure deployment process. It ensures that your infrastructure is correct, complete, and secure, and it can identify and address bugs early on. The types of tests you should run, syntax and linting, unit testing, integration testing, and acceptance testing, can catch different issues at different stages, and when done correctly, provide a foundation for a stable production environment.

While testing your infrastructure code may add some additional time initially, it will save time, resources, and bring more significant benefits later in the process, ensuring that you are delivering better software to your users in a repeatable and dependable manner.

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