Test file structure in Terraform - Step-by-Step Execution

Process Flow - Test file structure

Create test file

↓

Write test blocks

↓

Define resources and variables

↓

Run terraform test command

↓

Check test results

↓

Pass or Fail

This flow shows how a Terraform test file is created, written with test blocks, run, and checked for results.

Execution Sample

Terraform

terraform {
  required_version = ">= 1.5"
}

resource "null_resource" "example" {}

test "example_test" {
  check "basic" {
    assert {
      condition = true
      error_message = "Test failed"
    }
  }
}

This sample defines a simple Terraform configuration with a test block to check resource behavior.

Process Table

Step	Action	File Content	Command Run	Result
1	Create test file	test_example.tf with resource and test block		File created
2	Write test blocks	test block with checks added		Test defined
3	Run terraform test		terraform test	Tests executed
4	Check test results			Tests pass or fail
5	Exit	N/A	N/A	Testing complete

💡 All test steps completed, test results determine pass or fail

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
test_file	none	created	written	executed	results checked
test_result	none	none	none	running	pass/fail

Key Moments - 2 Insights

Why do we need a separate test file in Terraform?

Terraform separates test files to keep configuration and tests organized, as shown in step 1 and 2 of the execution_table.

What happens when we run 'terraform test'?

The command executes all test blocks in test files, shown in step 3, producing pass or fail results in step 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is the file content after step 2?

A Only resource definitions

B Test block with checks added

C Empty file

D Test results

💡 Hint

Refer to the 'File Content' column in row for step 2 in execution_table

At which step does the test execution happen?

A Step 1

B Step 4

C Step 3

D Step 5

💡 Hint

Check the 'Command Run' column in execution_table for the step running 'terraform test'

If the test file was not written correctly, what would change in the execution_table?

A Step 3 would show test execution failure

B Step 1 would fail to create file

C Step 5 would be skipped

D Step 2 would show empty file

💡 Hint

Look at step 3 and 4 results in execution_table for test execution and results

Concept Snapshot

Terraform test files are separate .tf files
They contain test blocks with checks
Run tests using 'terraform test' command
Tests show pass or fail results
Keep tests organized and separate from main config

Full Transcript

This visual execution shows how to create and run a Terraform test file. First, a test file is created and written with test blocks that define checks. Then, the 'terraform test' command runs these tests. Finally, results are checked to see if tests pass or fail. This separation helps keep configuration and tests organized.

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