Python Test Helper for Terraform

This simple helper facilitates testing Terraform modules from Python unit tests, by wrapping the Terraform executable and exposing convenience methods to set up fixtures, execute Terraform commands, and parse their output.

It allows for different types of tests: lightweight tests that only use Terraform init and plan to ensure code is syntactically correct and the right number and type of resources should be created, or full-fledged tests that run the full apply/output/destroy cycle, and can be then be used to test the actual created resources, or the state file.

As an additional convenience, the module also provides an easy way to request and access the plan output (via plan -out and show) and the outputs (via output -json), and can return them wrapped in simple classes that simplify accessing their attributes.

This module is heavily inspired by two projects: Terragrunt for the lightweight approach to testing Terraform, and python-terraform for wrapping the Terraform command in Python.

Example Usage

The test folder contains simple examples on how to write tests for both plan and apply, using either synthetic fixtures (simple representations of the plan output and output files), or minimal root modules. This is the test that uses plan output on an actual module:

import pytest
import tftest


@pytest.fixture
def plan(fixtures_dir):
  tf = tftest.TerraformTest('plan', fixtures_dir)
  tf.setup(extra_files=['plan.auto.tfvars'])
  return tf.plan(output=True)


def test_variables(plan):
  assert 'prefix' in plan.variables
  assert plan.variables['names'] == ['one', 'two']


def test_outputs(plan):
  assert sorted(plan.outputs['gcs_buckets'].keys()) == plan.variables['names']


def test_root_resource(plan):
  res = plan.resources['google_project_iam_member.test_root_resource']
  assert res['values']['project'] == plan.variables['project_id']


def test_modules(plan):
  mod = plan.modules['module.gcs-buckets']
  res = mod.resources['google_storage_bucket.buckets[0]']
  assert res['values']['location'] == plan.variables['gcs_location']

Compatibility

Starting from version 1.0.0 Terraform 0.12 is required, and tests written with previous versions of this module are incompatible. Check the CHANGELOG.md file for details on what's changed.

Testing

Tests use the pytest framework and have no other dependency except on the Terraform binary. The version used during development is in the DEV-REQUIREMENTS.txt file.

Disclaimer

This is not an officially supported Google product.