Testing features in Terraform overview

This topic provides an overview of the testing features in Terraform to help you validate your infrastructure.

Introduction

Terraform provides the following types of testing capabilities:

1. Configuration and infrastructure validation as part of your regular Terraform operations. Refer to Custom Conditions and Checks to learn more about these types of testing capabilities.
2. Traditional unit and integration testing on your configuration. Refer to the terraform test command documentation to learn more about this testing capability.

Additional testing and validation features

• Input Variable Validation
• Pre and Post-conditions
• Checks

How the terraform test command works

The test command performs the following actions:

• Locates Terraform testing files within your configuration directory.
• Provisions the infrastructure within your configuration as specified by each testing file.
• Runs the assertions from the test file against the provisioned infrastructure.
• Destroys the provisioned infrastructure at the end of the test.

For details about using the test command, refer to the test command reference documentation.

Write configuration for tests

Terraform test files have their own configuration syntax. This test file syntax focuses on customizing Terraform executions for the current configuration and overriding variables and providers to test different behaviors.

Validations

Validations allow you to verify aspects of your configuration and infrastructure as it is applied and created. HCP Terraform also supports automated continuous validation.

The Terraform test command also executes any validations within your configuration as part of the tests it executes. For more information on the available validation, refer to Checks and Custom Conditions.

Tests versus validations

You can write many validations as test assertions, but there are specific use cases for both.

Validations are executed during Terraform plan and apply operations, and the Terraform test command also runs validations while executing tests. Therefore, use validations to validate aspects of your configuration that should always be true and could impact the valid execution of your infrastructure.

Module authors should note that validations are executed and exposed to module users, so if they fail, ensure the failure messages are understandable and actionable.

In contrast, Terraform only executes tests when you run terraform test. Use tests to assert the correctness of any logical operations or specific behavior within your configuration. For example, you can test that Terraform creates conditional resources based on an input by setting the input controlling those resources to a certain value then verifying the resources Terraform creates.