BDD framework for Terraform – DZone

Behave, a Python-based behavior-driven development (BDD) framework for writing readable tests that describe the expected behavior of software systems. Terraform, on the other hand, is an infrastructure-as-code (IaC) tool that simplifies infrastructure management by allowing developers to define resources and configurations in a declarative manner. By combining the Behave BDD approach with Terraform, you can ensure that the infrastructure behaves as expected under different conditions. This integration facilitates early detection of problems and reliability of the infrastructure code.

Using Behave to test terraform

Testing Terraform configurations with Behave involves a series of structured steps:

Install Behave

Start by installing Behave and its dependencies using pip, Python’s package manager. This step ensures that Behave is ready for use in a test environment.

      pip install behave

Set up the directory structure

Organize test files and Terraform configurations in the directory structure that Behave expects. This structure typically includes separate directories for features, steps, and Terraform files, ensuring clarity and organization. For example:

.

├── features

│   └── terraform.feature

├── steps

│   └── step_implementation.py

├── terraform

	└── main.tf
    

Write file features

Use the Gherkin syntax to write feature files that describe the desired behavior of Terraform configurations. These feature files show scenarios and steps that test different aspects of the infrastructure code. Here is an example of a terraform.feature file:

  Feature: Verify EC2 actions
  
  	Scenario Outline: Check if the EC2 actions are allowed

    	Given I invoke <service>:<action>

    	When the region selected is <region>

    	Then the status should be <result>

Implementation step definitions

Develop step definitions in Python to define the behavior of each step specified in the feature files. These step definitions interact with Terraform commands, allowing infrastructure operations to be performed and results to be verified. Here is an example step_implementation.py file:

import os

from behave import *

 

@given('I invoke service:action')

def step_impl(context, service, action):

    context.action_name="".join([service, ':', action])

 

@when('the region selected is region')

def step_impl(context, region):

    os.environ['AWS_DEFAULT_REGION'] = region

 

@then('the status should be result')

def step_impl(context, result):

 action_name = []   

        action_name.append(context.action_name)

 		#Add assertions or checks for the action and results

Run the tests

Navigate to the root directory of tests and execute Behave to run the defined scenarios according to the Terraform configurations. During this step, Behave initializes and starts processing your test files. It reads feature files written in Gherkin syntax to understand the scenarios you’ve defined. Behave executes every scenario defined in your feature files. It compares each step in the script to the corresponding step definition in your Python code and executes them sequentially.

View test results

After executing the test, for each scenario defined in the feature files, Behave reports whether the scenario passed or failed. It also provides details of any steps within the scenario that failed, including the step definition and error message. Review these results to ensure that the Terraform configurations behave as expected and meet the desired criteria.

Conclusion

Following the structured approach above, you can use Behave to functionally test Terraform configurations. This process facilitates the identification of potential problems or deviations from expected behavior, ultimately increasing the correctness and reliability of infrastructure code. With Behave and Terraform working together, developers can adopt a systematic approach to testing and ensure the robustness of their infrastructure deployment.