Dealing with infrastructure can be a mess. Things can break in ways you would never think of, and the debugging can be a real pain. What if I told you there is a way to make all of this much easier? The secret lies in testing, a practice that is not always followed in the world of infrastructure as code. But the good news is, with tools like Terraform, you can bring testing to your infrastructure. Let’s take a look at how you can leverage infrastructure testing with Terraform to build more robust and reliable systems.
What is Infrastructure Testing?
Before we dive into the nitty-gritty, let’s first take a moment to define what infrastructure testing is. In the world of software development, you are probably already aware of unit, integration, and end-to-end testing, right? Well, infrastructure testing applies the same core concepts to the realm of your servers, networks, and other infrastructure components.
It’s all about validating that your infrastructure does what you expect it to do. This is a vital step that happens before you deploy code in production. This process can cover several aspects of infrastructure:
- Functionality: Does the infrastructure work? Does it do what it is supposed to do?
- Performance: Can the infrastructure handle the expected load and response times?
- Security: Are the necessary security measures in place and operating correctly?
- Compliance: Does the infrastructure meet the regulatory and policy requirements?
Without this vital step, you are mostly just hoping for the best. And that is never a good idea when it comes to important systems.
Why Test Infrastructure?
If you’re not testing your infrastructure, you’re playing a risky game. Here is a more in-depth look at the risks you are taking and what benefits you are missing out on.
Reduce Failures and Downtime: Catching issues before they hit production means less downtime. This will save you time and a ton of headaches. Nobody wants to wake up to an emergency caused by untested infrastructure, do they?
Improve Reliability: Testing ensures your infrastructure is reliable and consistent. This reduces the chance of unexpected behavior or performance drops.
Enhance Security: Testing helps find security flaws early. This can prevent expensive security incidents and protect sensitive data. By running security tests, you can be sure everything is up to snuff.
Increase Efficiency: Testing helps you find and fix problems faster, saving you precious time. This means less time debugging and more time deploying new and exciting updates.
Reduce Costs: By finding and fixing problems early, you reduce the cost of fixing them in production. And, less downtime means less money lost.
Enable Compliance: Testing makes sure your infrastructure meets regulatory and internal compliance rules. This will save you from penalties and bad press.
Types of Infrastructure Tests
There are a variety of testing types you can perform on your infrastructure. Here is a breakdown of the most common kinds.
Static Code Analysis: This kind of test does not execute code. Instead, it looks at the configuration files for common mistakes or violations of best practices. It is like having an automated code review process for your infrastructure code. You could find common errors, and you could also see where you are breaking any company policy.
Unit Tests: These tests check individual parts of your infrastructure. Things like single servers, network interfaces, or database setups. The point here is to make sure each part works as it should.
Integration Tests: These go further and test how different parts of your infrastructure interact with each other. You want to know how the server, the database, and other services all work together.
End-to-End Tests: This is the whole enchilada. It tests the full infrastructure stack, from the front end to the back end. It shows you how everything works together. This helps show whether your complete setup can handle user requests and business needs.
Performance Tests: This kind of testing helps determine how your infrastructure behaves under different load levels. You can see how it will perform with many users. Load, stress, and soak tests are all part of performance testing.
Security Tests: Here, you look for weak spots in your setup that could be used by bad actors. Penetration testing, vulnerability checks, and compliance scans are all part of this kind of test.
Why Infrastructure as Code and Terraform?
Infrastructure as Code (IaC) is the practice of managing and provisioning infrastructure using machine-readable definition files. Instead of manual work, you write code that defines what your servers, networks, and applications should look like. This approach lets you treat infrastructure like software. It lets you automate tasks, track changes, and reuse configurations.
Terraform is a very popular tool to implement IaC. With Terraform, you write declarative configuration files that describe the state of your infrastructure. Terraform then looks at these files to automate and manage infrastructure with different providers (AWS, Azure, Google Cloud, etc). Here’s what makes Terraform great for testing:
Repeatability: Terraform config files are consistent. You can create the exact same setup every time you run the code. This makes the testing process reliable and predictable. You can set up a test environment that mirrors production, so you can test under real conditions.
Version Control: Terraform config files are code. This means you can store it in a version control system like Git. This lets you track changes, collaborate with team members, and roll back to older versions. This also enables testing as code.
Automation: Terraform automates your infrastructure setup. This means you can automate tests too. By using pipelines and other automated methods, you can test your changes before they hit production.
Multi-Cloud Support: Terraform works with many cloud providers, so you can test your setup, no matter what platform you are using. This means that testing will look and feel the same if you have a multi-cloud strategy.
Setting up Terraform for Testing
Now, let’s talk about how you can set up Terraform for testing. It is not very hard, and it will save you time and stress down the line.
Create a Separate Test Environment
It is a very good idea to set up a test environment that is separate from your production setup. This environment will be a mirror of your production environment. It will allow you to run tests without the worry of affecting actual users. A good way to go about this is to have a separate state file for the test environment. You can also use different cloud resources. The goal here is to be able to test in an isolated way.
Version Control Your Terraform Code
Always use a version control system for your Terraform code. It is a best practice for any code, and it certainly applies to infrastructure as code. This makes tracking changes and collaborating easier. It also enables you to roll back to a previous version if a test reveals a problem.
Use Terraform Modules
Terraform modules are like functions for infrastructure. They group resources together to make the code more organized and easy to reuse. Modules make it very easy to test smaller parts of your system and increase the readability of your code. If you do not use modules, you will find that your configuration files will get very difficult to follow.
Incorporate Automated Testing Tools
There are a few tools that can help you integrate testing with Terraform. These tools help you write and run tests to ensure your infrastructure is working as expected. Here are a few that are worth looking at:
-
Terratest: This tool is a Go library that makes writing tests for Terraform code easier. It lets you test your infrastructure using familiar programming patterns.
-
InSpec: This is a tool that can be used to define compliance and security checks. It lets you test that the infrastructure meets these requirements.
-
KitchenCI: This tool is a test harness that lets you run tests against different cloud providers. You can use it to test your code locally, and in the cloud.
-
tfsec: This tool performs static analysis on your Terraform code. It looks for issues like security problems or deviations from best practices.
-
Checkov: This tool can perform static analysis as well, and it also looks for security issues in your code.
How to Test with Terraform: Practical Examples
Here are some ways to use the tools we mentioned earlier. Let’s look at a few examples to get you going.
Static Code Analysis with tfsec
Let’s say you’ve written some Terraform code that sets up an AWS S3 bucket. Here is what the code might look like.
resource "aws_s3_bucket" "example" {
bucket = "my-test-bucket"
acl = "public-read"
versioning {
enabled = false
}
}
Now, let’s use tfsec to look for issues with this code. To start, you will need to download and install tfsec on your machine. You can do this by following the steps on its GitHub page.
Once you have tfsec, you can run the following command in your terminal from the directory where your Terraform file is located:
tfsec .
tfsec will analyze your code and give you a report of the issues it found. Here is what the result might look like:
[s3-003] S3 bucket has an ACL defined which allows public access.
/main.tf:3
3 | acl = "public-read"
tfsec has found that your S3 bucket has public read access. This could lead to security problems. To fix this, you would need to remove the acl = "public-read" line, or change it to be more restrictive.
Unit Testing with Terratest
Now, let’s look at unit testing with Terratest. Let’s suppose you created a module for creating an EC2 instance. Here is the Terraform code that defines the module:
resource "aws_instance" "example" {
ami = var.ami
instance_type = var.instance_type
tags = {
Name = var.name
}
}
Now, let’s use Terratest to create a unit test that verifies this code. You will first need to download and install Go. And then you can install Terratest by running this command in your terminal:
go get github.com/gruntwork-io/terratest/v4
Once you have installed Go and Terratest, you can create a test file (ex: example_test.go) in the same directory where you have your module. Here’s what the test code might look like:
package test
import (
"testing"
"github.com/gruntwork-io/terratest/modules/terraform"
"github.com/stretchr/testify/assert"
)
func TestEC2Module(t *testing.T) {
terraformOptions := terraform.WithDefaultRetryableErrors(t, &terraform.Options{
TerraformDir: ".",
Vars: map[string]interface{}{
"ami": "ami-0c55b7451a5d60603",
"instance_type": "t2.micro",
"name": "test-instance",
},
})
defer terraform.Destroy(t, terraformOptions)
terraform.InitAndApply(t, terraformOptions)
instanceName := terraform.Output(t, terraformOptions, "name")
assert.Equal(t, "test-instance", instanceName)
instanceType := terraform.Output(t, terraformOptions, "instance_type")
assert.Equal(t, "t2.micro", instanceType)
ami := terraform.Output(t, terraformOptions, "ami")
assert.Equal(t, "ami-0c55b7451a5d60603", ami)
}
This test does a few things: It applies the Terraform code, then it looks at the output of the name, instance_type, and ami fields. Then it verifies that the output matches the values we provided.
To run this test, run the following command from the same directory where your test file is located:
go test -v .
If the test is successful, you should see output that is similar to this:
=== RUN TestEC2Module
--- PASS: TestEC2Module (3.49s)
PASS
ok test 3.503s
This means that your module works as it should.
Integration Testing with KitchenCI
Now, let’s look at how to use KitchenCI to perform integration tests. With this tool, we can see how different pieces of our infrastructure will work together.
To start, you will need to download and install Ruby, then install KitchenCI by running this command in your terminal:
gem install kitchen-terraform
Also, you will need to install a driver for KitchenCI. In this case, we will use the AWS driver.
gem install kitchen-ec2
Once you have installed the required libraries, you can create a file named .kitchen.yml with the configuration. Here is an example configuration:
driver:
name: ec2
region: us-west-2
aws_ssh_key_id: "<Your SSH key ID>"
associate_public_ip: true
transport:
name: ssh
provisioner:
name: terraform
suites:
default:
driver:
instance_type: t2.micro
provisioner:
root_module_path: "."
variables:
ami: "ami-0c55b7451a5d60603"
# Test specific actions
client_actions:
- action: "output"
output: "instance_type"
This configuration file sets up the connection parameters to your AWS account, and some default instance properties, like its type.
To run your tests, you will need to run kitchen converge default to apply the code using terraform, and then run kitchen verify default to perform tests. You can also run kitchen test default which will do both tasks one after another.
This command will apply your Terraform code and check that the output variable instance_type exists and is the value that you expect to find.
End-to-End Testing with Terratest
For an end-to-end test with Terratest, we will need to create more infrastructure than in the previous example. Let’s suppose you want to make sure that your website works as expected. So you will want to make sure your web server and load balancer all work together.
First, we need to set up the infrastructure with Terraform. Here is an example of what this might look like:
#Create an EC2 instance
resource "aws_instance" "web_server" {
ami = "ami-0c55b7451a5d60603"
instance_type = "t2.micro"
user_data = <<-EOF
#!/bin/bash
yum update -y
yum install httpd -y
systemctl enable httpd
systemctl start httpd
echo "<h1>Hello from my web server!</h1>" > /var/www/html/index.html
EOF
tags = {
Name = "web-server"
}
}
#Create a load balancer
resource "aws_lb" "web_load_balancer" {
load_balancer_type = "application"
subnets = [
"subnet-0bb1c79de3EXAMPLE",
"subnet-002e460f61EXAMPLE",
]
security_groups = ["sg-040475f639EXAMPLE"]
}
#Create a target group
resource "aws_lb_target_group" "web_target_group" {
port = 80
protocol = "HTTP"
vpc_id = "vpc-084080584aEXAMPLE"
}
#Attach the instance to the target group
resource "aws_lb_target_group_attachment" "web_target_group_attachment" {
target_group_arn = aws_lb_target_group.web_target_group.arn
target_id = aws_instance.web_server.id
port = 80
}
#Create a listener for the load balancer
resource "aws_lb_listener" "web_listener" {
load_balancer_arn = aws_lb.web_load_balancer.arn
port = "80"
protocol = "HTTP"
default_action {
type = "forward"
target_group_arn = aws_lb_target_group.web_target_group.arn
}
}
#Make load balancer output variable
output "load_balancer_dns_name" {
value = aws_lb.web_load_balancer.dns_name
}
This creates a basic web server, an application load balancer, a target group, and a listener.
Now, we can create a test file to check the website (example: web_test.go) in the same directory as your main.tf file:
package test
import (
"testing"
"time"
"fmt"
"net/http"
"io"
"github.com/gruntwork-io/terratest/modules/terraform"
"github.com/stretchr/testify/assert"
)
func TestWebsite(t *testing.T) {
terraformOptions := terraform.WithDefaultRetryableErrors(t, &terraform.Options{
TerraformDir: ".",
})
defer terraform.Destroy(t, terraformOptions)
terraform.InitAndApply(t, terraformOptions)
lbDNS := terraform.Output(t, terraformOptions, "load_balancer_dns_name")
url := fmt.Sprintf("http://%s", lbDNS)
// Wait for the load balancer to become available
time.Sleep(5 * time.Minute)
resp, err := http.Get(url)
assert.NoError(t, err)
defer resp.Body.Close()
assert.Equal(t, http.StatusOK, resp.StatusCode)
body, err := io.ReadAll(resp.Body)
assert.NoError(t, err)
assert.Contains(t, string(body), "Hello from my web server!")
}
This test will do a few things: It will first create the infrastructure. Then it will wait 5 minutes. This gives the load balancer and web server enough time to become available. After waiting, the test will send a request to the load balancer endpoint. Finally, the test will make sure that the response has a 200 OK status and that the body contains the text “Hello from my web server!”.
To run this test, you can run the following command from the directory where your file is located:
go test -v .
If the test is successful, you should see output similar to this:
=== RUN TestWebsite
--- PASS: TestWebsite (308.44s)
PASS
ok test 308.483s
This indicates that the test worked as expected.
Best Practices for Testing Terraform Infrastructure
Here are a few best practices that you can follow to improve your testing strategy.
Write Tests Early: Start writing tests as soon as you start to write your Terraform code. This helps you catch issues early on, which is a lot cheaper than fixing problems in production. Think about testing the moment you begin to code.
Use Test Driven Development (TDD): If you take it to the next level, you can use test-driven development, which means you write your tests before you write any code. This means that you have tests ready as soon as the code is ready.
Test in Isolation: Make sure your tests run in isolation. So they do not interfere with each other. Each test should only test one thing, and not depend on other tests.
Test Frequently: You should always test your code whenever you make a change. By setting up a CI pipeline, you will always catch issues before they affect anything else.
Use Mock Data: Mock external API calls and services in your tests. This will make your tests run faster and more reliably.
Keep it Simple: Do not write tests that are too complex. Simple tests are easier to understand, maintain, and debug.
Review Your Tests: Always review your tests with your team, just as you review your code. This helps you maintain a consistent and well-tested infrastructure code.
Use Automated Pipelines: Automate your tests with tools like GitHub Actions, Jenkins, or GitLab CI. This lets you test and deploy your infrastructure code with more confidence.
The Future of Terraform Testing
As infrastructure as code becomes more vital, the need for effective testing will grow. Tools and best practices will become more sophisticated. Here are a few trends that you can expect to see.
AI-Driven Testing: AI and Machine Learning could be used to look at test results to detect bugs, predict failures, and make testing better. This will help reduce the time you need to test your infrastructure code.
Cloud-Native Testing: Tests will be built to work better in cloud-native environments. This means tests will become more dynamic and scale well with the cloud.
Security Testing: Automated security tests and compliance checks will be a normal part of infrastructure testing. This will make sure all systems are both secure and meet all guidelines.
Integration of Tests: Tools and frameworks will continue to improve and make integrating infrastructure tests into your workflows and pipelines easier. This will make testing a more normal part of the IaC process.
Shift-Left Testing: As DevOps moves forward, testing will be done earlier in the development process. By testing early, you will catch issues before they become expensive to fix.
A Safe and Robust Infrastructure
Testing your infrastructure with Terraform is more than just a good idea. It is a very important step to building a safe and reliable infrastructure. This will help you prevent downtime, reduce costs, and increase efficiency.
By implementing the test methods that we talked about in this article, you will be well on your way to a robust and more reliable infrastructure. So start using tests today and create systems that are both safe and reliable.