Terratest: Automating Infrastructure Testing

As any other prospective ideology of DevOps and cloud infrastructure broadly visualized, testing would be equally, if not more, essential. With the coming of IaC tools like Terraform, preferential focus on the reliability and correctness of infrastructure became a given. This is where Terratest comes into play. Terratest is, much like its name suggests, an automated testing library written in the Go language that helps to write tests for the infrastructure code.

This blog will discuss everything you need about Terratest, from its basic principles to workings and undertakings.

What is Terratest?

Gruntwork’s open-source library allows the writing of automated test cases against infrastructure code using Terraform and other tools such as Packer, Kubernetes, and more, known as Terratest. Terratest is run directly in the IaC workflows and minimizes misconfigurations, shortens deployment time, and bolsters the strength of infrastructure for the teams. This tool completes the missing link between development and operation by adapting software testing methodologies to the field of infrastructure. Terratest for IaC should be used most strongly by those teams that are aimed at the reliability, scaling, and automation of work.

Terratest enables you through the power of Go to accomplish the following:

1. To check whether your infrastructure settings are correct or not.
2. To move the bugs towards the left side of the development lifecycle by running the tests inside the CI/CD pipelines,
3. To ensure that the infrastructure meets the set expectations in all environments.

Why Terratest?

1. Automated Testing Of IaC: Terratest will allow the effortless automation of testing against infrastructure code.
2. Continuous: It easily fits into the CI/CD pipelines and allows tests to run continuously.
3. Realistic Testing: It will enable the deployment of test infrastructure to run tests in a realistic scenario.
4. Give Modular and Reusable Test Functions: It creates modular structures and allows the reusability of test functions.
5. Compatibility: This is accompanied by its compatibility with widely used IaC solutions, including Terraform and Kubernetes.

Now, why should teams use Terratest in their IaC?

By including Terratest within your IaC, you get several reasons why It will make the infrastructure better, faster, more reliable, and easier to manage. Here are why teams need to adopt it.

1. Catch Errors Early: Without testing, mistakes committed when making IaC configurations can only be noticed during the deployment stage. This can be very costly since it can lead to poor system availability or service disruption. Terratest allows you to use real-world environments to test your changes before you apply your Terraform scripts or any other IaC tool.
2. Automation and CI/CD Integration: Remote infrastructure validation, for instance, is not only tiresome and time-consuming but also delicate. It requires a lot of work and often ends up being done in vain due to errors. It is integrated with the CI/CD pipelines so that each team validates their changes with Terratest before implementation.
3. Confidence in Infrastructure: This then leads to some configuration-related issues in infrastructure including security flaws, non-compliance, or poor performance. Before roll-out, they ensure that the vital features for configurations like network rules, instance sizes, and system availability are checked so that the teams become confident about them when using the configurations.
4. Real-world testing: Time-bound evaluations such as mock tests and partial validations are normally unique and hard to reproduce at short notice. Terratest provisions the actual infrastructure and tests and therefore checks the final behavior in a running environment, also verifying DNS resolution, load balancers, or database connection.
5. Built-in Retry Logic: When utilizing cloud resources, tests can take time to stabilize, and tests commonly become fluffy in traditional testing frameworks. Since eventual consistency is a common problem across numerous systems, Terratest comes with retry mechanisms that assist the user in handling them, making the tests more reliable and resilient.
6. Reusability and Modularity: Writing a test for each module of IaC would be pointless and redundant. Terratest offers myriad interchangeable patches and templates, making it efficient to execute numerous arrangements without the need to code for them.
7. Cost Optimization: Long and unproductive resource consumption results in high costs, which may be attributed to the cloud. This way, Terratest can guarantee full validation yet maintain durability by destroying resources as soon as the tests are run to prevent the unnecessary incurring of costs.
8. Maintains Compliance and Security: Solutions that are non-compliant or securely configured can lead to rather large regulatory fines or hacks. You can now create tests to ensure compliance with standards such as HIPAA, PCI-DSS, or even other good practices in configurations.
9. Enable Team Collaboration: Testing infractions, as they are sometimes called, usually end up isolated or become heterogeneous across different teams. The paradigm of prescriptive templates facilitates the pursuance of good testing practices within and across teams and projects.
10. Ease Testing of Complex Infrastructures: The high level of complexity inherent in prototyping implies that multi-tenant or multi-region deployments or failover scenarios are particularly difficult to exercise. Terratest enables the creation and running of the many architectures involved in a project to ensure that they operate as designed once deployed in the field.
11. Integration with Existing Tooling: A new tool disrupts coming in an existing working model. Terratest works well with the most innovative platforms, such as Terraform, Packer, Docker, and Kubernetes which many organizations already use, therefore, the adoption of Terratest will not be challenging.
12. Continuous Improvement: Static infrastructure validation does not account for changes in conditions or growth needs. Terratest is self-sustainable from this perspective because it effectively tests, evolves, and optimizes the infrastructure in successive iterations.

Prerequisites

1. Before diving into Terratest, you need the following:
2. In this case, local installation of Terraform is assumed.
3. Go installed, because Terratest is a Go library.
4. Some understanding of what Terraform or the Go programming language is.
5. A live certified cloud provider account with Amazon Web Service (AWS), Microsoft Azure, Google Cloud (GCP), etc.

Getting Started with Terratest: Code Walk-Through!

The code demonstrates how to use Terratest to validate the network configuration of an Azure Virtual Machine deployed using Terraform. Below are the steps:

Test Setup

The code begins by importing the necessary modules:

• Terratest modules for Azure and Terraform.
• Testify's assert package for validations.
• Go’s testing package is used to run the tests.

Main Test Function

The core test function is TestTerraformAzureVmExample:

Here’s what happens step-by-step:

1. t.Parallel() enables parallel test execution.
2. The Azure subscription ID is defined (replace the placeholder with your actual subscription ID).
3. Terraform Options specify the location of the Terraform configuration directory (../resources).
4. The Terraform lifecycle is handled:

• Terraform.InitAndApply(...): Initializes and deploys resources.

• Defer terraform.Destroy(...): Cleans up resources after the test completes.

5. The network configuration validation is delegated to a helper function, testNetworkOfVM.

Network Configuration Validation

The function testNetworkOfVM tests several validations to ensure the Azure VM is deployed correctly, mainly on its network configuration.
This function retrieves the following outputs from the Terraform configuration:

1. Resource Group Name
2. Virtual Machine Name
3. Virtual Network Name
4. Subnet Name
5. Public IP Address
6. Network Interface Name
7. Private IP Address

ValidationsThe key validations in the code are the following:

1. Virtual Network Subnet Validation: This is to ensure that the expected subnets are present in the virtual network.
2. Validate private IP in subnet: This is checking whether the private IP of the VM resides in the correct subnet.
3. Validate network interface: It checks that the appropriate network interface is attached to the VM.
4. Validate NIC count: This validates that the VM has one network interface attached.
5. Validate private IP: This test validates that the private IP matches the expected IP.
6. Validate public IP: This test ensures that the public IP address of the VM is correctly configured.

Best practices

1. Modular Tests: Create test cases for the tasks that will most likely be tested.
   Resource
2. Cleanup: By default, never use `terraform.Destroy()` You should always use `defer terraform.Destroy()`.
3. Parallel Testing: Run your tests in parallel using the testing package in Go.
   Keep Tests Small: Gradually focus on one aspect of your infrastructure when trying a test.
4. Version Control: To have more control over the versions of the code being used, fix versions of both Terraform and Terratest modules.

Conclusion

Terratest is excellent for testing infrastructure code as a second layer. This ensures the reliability of the tests with reduced manual work and increases the quality of the tests by improving the deployment. Whether it is deploying a simple application or building a multi-cloud environment for business, Terratest helps make the process solid and safe.
Start with a few features, write their corresponding valuable tests, and then expand between capability expansions. Happy testing!