Test file structure in Terraform - Mini Project: Build & Apply

Terraform Test File Structure

📖 Scenario: You are working on a Terraform project to manage cloud infrastructure. To ensure your Terraform code is organized and testable, you want to create a proper test file structure.

🎯 Goal: Create a Terraform test file structure with a main configuration file and a test file that references it.

📋 What You'll Learn

Create a Terraform configuration file named main.tf with a simple resource

Create a test file named main_test.tf that references the resource from main.tf

Use valid Terraform syntax and best practices for file naming and structure

💡 Why This Matters

🌍 Real World

Organizing Terraform files properly helps teams manage infrastructure code clearly and test resources effectively.

💼 Career

Understanding Terraform file structure and testing is essential for cloud engineers and DevOps professionals managing infrastructure as code.

1

Create main.tf with a simple resource

Create a Terraform configuration file named main.tf that defines an AWS S3 bucket resource called example_bucket with the bucket name my-example-bucket.

Terraform

# Your code here to create main.tf with an AWS S3 bucket resource

Hint

Use the resource block with type aws_s3_bucket and name example_bucket. Set the bucket attribute to "my-example-bucket".

2

Create main_test.tf with a test reference

Create a Terraform test file named main_test.tf that references the example_bucket resource from main.tf using a data block of type aws_s3_bucket and name test_bucket. Set the bucket attribute to aws_s3_bucket.example_bucket.bucket.

Terraform

resource "aws_s3_bucket" "example_bucket" {
  bucket = "my-example-bucket"
}

# Your code here to create main_test.tf with a data block referencing example_bucket

Hint

Use a data block to reference the existing bucket resource by its bucket name.

3

Add a terraform block with required provider

Add a terraform block to main.tf specifying the required provider aws with version constraint "~> 4.0".

Terraform

resource "aws_s3_bucket" "example_bucket" {
  bucket = "my-example-bucket"
}

terraform {
  # Your code here to add required_providers
}

data "aws_s3_bucket" "test_bucket" {
  bucket = aws_s3_bucket.example_bucket.bucket
}

Hint

The terraform block should include required_providers with aws provider and version constraint.

4

Add provider configuration for AWS

Add a provider block for aws in main.tf with the region set to us-east-1.

Terraform

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 4.0"
    }
  }
}

# Your code here to add provider configuration

resource "aws_s3_bucket" "example_bucket" {
  bucket = "my-example-bucket"
}

data "aws_s3_bucket" "test_bucket" {
  bucket = aws_s3_bucket.example_bucket.bucket
}

Hint

Add a provider block for AWS with the region attribute set.

Practice

1. What is the main reason to keep Terraform test files separate from production code files?

easy

A. Because Terraform does not support test files inside the main folder

B. To avoid mixing test code with production code and keep the project organized

C. To reduce the size of the Terraform state file

D. Because test files must be written in a different language

Solution

1. Step 1: Understand file organization purpose

   Separating test files helps keep the project clean and easier to manage by not mixing test and production code.

2. Step 2: Recognize Terraform best practices

   Terraform encourages clear separation to avoid confusion and accidental deployment of test code.

3. Final Answer:

   To avoid mixing test code with production code and keep the project organized -> Option B

4. Quick Check:

   Separate test files = organized project [OK]

Hint: Keep test files separate to avoid confusion [OK]

Common Mistakes:

• Thinking test files must be in main folder
• Believing test files affect state size
• Assuming test files require different language

2. Which of the following is the correct folder structure for organizing Terraform files including tests?

easy

A. /main.tf, /variables.tf, /outputs.tf, /test/main_test.tf

B. /main.tf, /variables.tf, /outputs.tf, /modules/tests/test_main.tf

C. /main.tf, /variables.tf, /outputs.tf, /tests/test_main.tf

D. /main.tf, /variables.tf, /outputs.tf, /tests/main_test.tf

Solution

1. Step 1: Identify standard test folder naming

   Tests are usually placed in a separate folder named 'tests' at the root level for clarity.

2. Step 2: Check file naming conventions

   Test files often have '_test' suffix to indicate their purpose, e.g., 'main_test.tf'.

3. Final Answer:

   /main.tf, /variables.tf, /outputs.tf, /tests/main_test.tf -> Option D

4. Quick Check:

   Tests folder with *_test.tf files = correct structure [OK]

Hint: Use 'tests' folder with *_test.tf files [OK]

Common Mistakes:

• Placing tests inside modules folder
• Naming test folder as 'test' instead of 'tests'
• Not using _test suffix for test files

3. Given this Terraform project structure:

/main.tf
/variables.tf
/outputs.tf
/tests/test_main.tf

What will happen if you run terraform apply from the root directory?

medium

A. Terraform will apply infrastructure defined in main.tf and ignore test files

B. Terraform will apply both main.tf and test_main.tf causing errors

C. Terraform will only apply test_main.tf and ignore main.tf

D. Terraform will fail because test files are not allowed

Solution

1. Step 1: Understand Terraform file loading behavior

   Terraform loads *.tf files in the current directory but ignores files in subfolders unless explicitly included.

2. Step 2: Recognize test folder separation effect

   Files inside /tests are not loaded by default during terraform apply, so only main.tf and related files are applied.

3. Final Answer:

   Terraform will apply infrastructure defined in main.tf and ignore test files -> Option A

4. Quick Check:

   Terraform applies root *.tf files only [OK]

Hint: Terraform ignores test folder files by default [OK]

Common Mistakes:

• Assuming terraform applies all .tf files recursively
• Thinking test files run automatically
• Believing terraform apply fails due to test files

4. You have this folder structure:

/main.tf
/variables.tf
/outputs.tf
/tests/test_main.tf

Running terraform apply gives an error about duplicate resource definitions. What is the likely cause?

medium

A. Outputs are missing in outputs.tf

B. Variables are defined twice in variables.tf

C. Terraform is loading test_main.tf and main.tf causing duplicate resources

D. Terraform state file is corrupted

Solution

1. Step 1: Analyze error cause

   Duplicate resource errors usually mean Terraform sees the same resource defined more than once.

2. Step 2: Check file loading

   If test files are accidentally loaded (e.g., by running terraform in /tests), resources duplicate with main.tf definitions.

3. Final Answer:

   Terraform is loading test_main.tf and main.tf causing duplicate resources -> Option C

4. Quick Check:

   Duplicate resources = multiple files loaded [OK]

Hint: Run terraform only in root, not in tests folder [OK]

Common Mistakes:

• Blaming variables or outputs for duplicate resource error
• Ignoring that test files can cause duplicates if loaded
• Assuming state file corruption without checking files

5. You want to reuse infrastructure code in multiple projects and keep tests separate. Which folder structure best supports this using Terraform modules and tests?

hard

A. /modules/network/main.tf, /modules/network/variables.tf, /tests/network_test.tf, /main.tf

B. /network/main.tf, /network/variables.tf, /tests/network_test.tf, /main.tf

C. /modules/network/main.tf, /tests/network/main_test.tf, /main.tf

D. /modules/network/main.tf, /modules/network/tests/network_test.tf, /main.tf

Solution

1. Step 1: Identify module folder best practice

   Modules should be inside a 'modules' folder with their own files for reuse.

2. Step 2: Separate tests outside modules

   Tests should be in a top-level 'tests' folder to avoid mixing with reusable module code.

3. Final Answer:

   /modules/network/main.tf, /modules/network/variables.tf, /tests/network_test.tf, /main.tf -> Option A

4. Quick Check:

   Modules in 'modules', tests in 'tests' folder [OK]

Hint: Keep modules and tests in separate top-level folders [OK]

Common Mistakes:

• Placing tests inside modules folder
• Not using a modules folder for reusable code
• Mixing test files with main project files