How to test infrastructure code: automated testing for Terraform, Kubernetes, Docker, Packer and more

Automated testing for: ✓ terraform ✓ docker ✓ packer ✓ kubernetes ✓ and more Passed: 5. Failed: 0. Skipped: 0. Test run successful. How to test infrastructure code

The DevOps world is full of Fear

“Fear leads to anger. Anger leads to hate. Hate leads to suffering.” Scrum Master Yoda

And you all know what suffering leads to, right?

Many DevOps teams deal with this fear in two ways:

Sadly, both of these just make the problem worse!

There’s a better way to deal with this fear:

Automated tests give you the confidence to make changes

We know how to write automated tests for application code…

resource "aws_lambda_function" "web_app" { function_name = var.name role = aws_iam_role.lambda.arn # ... } resource "aws_api_gateway_integration" "proxy" { type = "AWS_PROXY" uri = aws_lambda_function.web_app.invoke_arn # ... } But how do you test your Terraform code deploys infrastructure that works?

apiVersion: apps/v1 kind: Deployment metadata: name: hello-world-app-deployment spec: selector: matchLabels: app: hello-world-app replicas: 1 spec: containers: - name: hello-world-app image: gruntwork-io/hello-world-app:v1 ports: - containerPort: 8080 How do you test your Kubernetes code configures your services correctly?

This talk is about how to write tests for your infrastructure code.

I’m Yevgeniy Brikman ybrikman.com

Co-founder of Gruntwork gruntwork.io

1. Static analysis 2. Unit tests 3. Integration tests 4. End-to-end tests 5. Conclusion Outline

Static analysis: test your code without deploying it.

Static analysis 1. Compiler / parser / interpreter 2. Linter 3. Dry run

Statically check your code for syntactic and structural issues

Tool Command Terraform terraform validate Packer packer validate <template> Kubernetes kubectl apply -f <file> --dry-run --validate=true Examples:

Statically validate your code to catch common errors

Tool Linters Terraform 1. conftest 2. terraform_validate 3. tflint Docker 1. dockerfile_lint 2. hadolint 3. dockerfilelint Kubernetes 1. kube-score 2. kube-lint 3. yamllint Examples:

Partially execute the code and validate the “plan”, but don’t actually deploy

Tool Dry run options Terraform 1. terraform plan 2. HashiCorp Sentinel 3. terraform-compliance Kubernetes kubectl apply -f <file> --server-dry-run Examples:

Unit tests: test a single “unit” works in isolation.

Unit tests 1. Unit testing basics 2. Example: Terraform unit tests 3. Example: Docker/Kubernetes unit tests 4. Cleaning up after tests

You can’t “unit test” an entire end- to-end architecture

Instead, break your infra code into small modules and unit test those! module module module module module module module module module module module module module module module

With app code, you can test units in isolation from the outside world

resource "aws_lambda_function" "web_app" { function_name = var.name role = aws_iam_role.lambda.arn # ... } resource "aws_api_gateway_integration" "proxy" { type = "AWS_PROXY" uri = aws_lambda_function.web_app.invoke_arn # ... } But 99% of infrastructure code is about talking to the outside world…

resource "aws_lambda_function" "web_app" { function_name = var.name role = aws_iam_role.lambda.arn # ... } resource "aws_api_gateway_integration" "proxy" { type = "AWS_PROXY" uri = aws_lambda_function.web_app.invoke_arn # ... } If you try to isolate a unit from the outside world, you’re left with nothing!

So you can only test infra code by deploying to a real environment

Key takeaway: there’s no pure unit testing for infrastructure code.

Therefore, the test strategy is: 1. Deploy real infrastructure 2. Validate it works (e.g., via HTTP requests, API calls, SSH commands, etc.) 3. Undeploy the infrastructure (So it’s really integration testing of a single unit!)

Tool Deploy / Undeploy Validate Works with Terratest Yes Yes Terraform, Kubernetes, Packer, Docker, Servers, Cloud APIs, etc. kitchen-terraform Yes Yes Terraform Inspec No Yes Servers, Cloud APIs Serverspec No Yes Servers Goss No Yes Servers Tools that help with this strategy:

Tool Deploy / Undeploy Validate Works with Terratest Yes Yes Terraform, Kubernetes, Packer, Docker, Servers, Cloud APIs, etc. kitchen-terraform Yes Yes Terraform Inspec No Yes Servers, Cloud APIs Serverspec No Yes Servers Goss No Yes Servers In this talk, we’ll use Terratest:

Sample code for this talk is at: github.com/gruntwork-io/infrastructure-as-code-testing-talk

An example of a Terraform module you may want to test:

infrastructure-as-code-testing-talk └ examples └ hello-world-app └ main.tf └ outputs.tf └ variables.tf └ modules └ test └ README.md hello-world-app: deploy a “Hello, World” web service

resource "aws_lambda_function" "web_app" { function_name = var.name role = aws_iam_role.lambda.arn # ... } resource "aws_api_gateway_integration" "proxy" { type = "AWS_PROXY" uri = aws_lambda_function.web_app.invoke_arn # ... } Under the hood, this example runs on top of AWS Lambda & API Gateway

$ terraform apply Outputs: url = ruvvwv3sh1.execute-api.us-east-2.amazonaws.com $ curl ruvvwv3sh1.execute-api.us-east-2.amazonaws.com Hello, World! When you run terraform apply, it deploys and outputs the URL

Let’s write a unit test for hello-world-app with Terratest

infrastructure-as-code-testing-talk └ examples └ modules └ test └ hello_world_app_test.go └ README.md Create hello_world_app_test.go

func TestHelloWorldAppUnit(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/hello-world-app", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) validate(t, terraformOptions) } The basic test structure

func TestHelloWorldAppUnit(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/hello-world-app", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) validate(t, terraformOptions) } 1. Tell Terratest where your Terraform code lives

func TestHelloWorldAppUnit(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/hello-world-app", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) validate(t, terraformOptions) } 2. Run terraform init and terraform apply to deploy your module

func TestHelloWorldAppUnit(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/hello-world-app", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) validate(t, terraformOptions) } 3. Validate the infrastructure works. We’ll come back to this shortly.

func TestHelloWorldAppUnit(t *testing.T) { terraformOptions := &terraform.Options{ TerraformDir: "../examples/hello-world-app", } defer terraform.Destroy(t, terraformOptions) terraform.InitAndApply(t, terraformOptions) validate(t, terraformOptions) } 4. Run terraform destroy at the end of the test to undeploy everything

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } The validate function

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } 1. Run terraform output to get the web service URL

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } 2. Make HTTP requests to the URL

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } 3. Check the response for an expected status and body

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } 4. Retry the request up to 10 times, as deployment is asynchronous

Note: since we’re testing a web service, we use HTTP requests to validate it.

Infrastructure Example Validate with… Example Web service Dockerized web app HTTP requests Terratest http_helper package Server EC2 instance SSH commands Terratest ssh package Cloud service SQS Cloud APIs Terratest aws or gcp packages Database MySQL SQL queries MySQL driver for Go Examples of other ways to validate:

$ export AWS_ACCESS_KEY_ID=xxxx $ export AWS_SECRET_ACCESS_KEY=xxxxx To run the test, first authenticate to AWS

$ go test -v -timeout 15m -run TestHelloWorldAppUnit … --- PASS: TestHelloWorldAppUnit (31.57s) Then run go test. You now have a unit test you can run after every commit!

What about other tools, such as Docker + Kubernetes?

infrastructure-as-code-testing-talk └ examples └ hello-world-app └ docker-kubernetes └ Dockerfile └ deployment.yml └ modules └ test └ README.md docker-kubernetes: deploy a “Hello, World” web service to Kubernetes

FROM ubuntu:18.04 EXPOSE 8080 RUN DEBIAN_FRONTEND=noninteractive apt-get update && apt-get install -y busybox RUN echo 'Hello, World!' > index.html CMD ["busybox", "httpd", "-f", "-p", "8080"] Dockerfile: Dockerize a simple “Hello, World!” web service

apiVersion: apps/v1 kind: Deployment metadata: name: hello-world-app-deployment spec: selector: matchLabels: app: hello-world-app replicas: 1 spec: containers: - name: hello-world-app image: gruntwork-io/hello-world-app:v1 ports: - containerPort: 8080 deployment.yml: define how to deploy a Docker container in Kubernetes

$ cd examples/docker-kubernetes $ docker build -t gruntwork-io/hello-world-app:v1 . Successfully tagged gruntwork-io/hello-world-app:v1 $ kubectl apply -f deployment.yml deployment.apps/hello-world-app-deployment created service/hello-world-app-service created $ curl localhost:8080 Hello, World! Build the Docker image, deploy to Kubernetes, and check URL

Let’s write a unit test for this code.

infrastructure-as-code-testing-talk └ examples └ modules └ test └ hello_world_app_test.go └ docker_kubernetes_test.go └ README.md Create docker_kubernetes_test.go

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } The basic test structure

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 1. Build the Docker image. You’ll see the buildDockerImage method shortly.

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 2. Tell Terratest where your Kubernetes deployment is defined

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 3. Configure kubectl options to authenticate to Kubernetes

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 4. Run kubectl apply to deploy the web app to Kubernetes

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 5. Check the app is working. You’ll see the validate method shortly.

func TestDockerKubernetes(t *testing.T) { buildDockerImage(t) path := "../examples/docker-kubernetes/deployment.yml" options := k8s.NewKubectlOptions("", "", "") defer k8s.KubectlDelete(t, options, path) k8s.KubectlApply(t, options, path) validate(t, options) } 6. At the end of the test, remove all Kubernetes resources you deployed

func buildDockerImage(t *testing.T) { options := &docker.BuildOptions{ Tags: []string{"gruntwork-io/hello-world-app:v1"}, } path := "../examples/docker-kubernetes" docker.Build(t, path, options) } The buildDockerImage method

func validate(t *testing.T, opts *k8s.KubectlOptions) { k8s.WaitUntilServiceAvailable(t, opts, "hello-world- app-service", 10, 1*time.Second) http_helper.HttpGetWithRetry(t, serviceUrl(t, opts), // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3*time.Second // Time between retries ) } The validate method

func validate(t *testing.T, opts *k8s.KubectlOptions) { k8s.WaitUntilServiceAvailable(t, opts, "hello-world- app-service", 10, 1*time.Second) http_helper.HttpGetWithRetry(t, serviceUrl(t, opts), // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3*time.Second // Time between retries ) } 1. Wait until the service is deployed

func validate(t *testing.T, opts *k8s.KubectlOptions) { k8s.WaitUntilServiceAvailable(t, opts, "hello-world- app-service", 10, 1*time.Second) http_helper.HttpGetWithRetry(t, serviceUrl(t, opts), // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3*time.Second // Time between retries ) } 2. Make HTTP requests

func validate(t *testing.T, opts *k8s.KubectlOptions) { k8s.WaitUntilServiceAvailable(t, opts, "hello-world- app-service", 10, 1*time.Second) http_helper.HttpGetWithRetry(t, serviceUrl(t, opts), // URL to test 200, // Expected status code "Hello, World!", // Expected body 10, // Max retries 3*time.Second // Time between retries ) } 3. Use serviceUrl method to get URL

func serviceUrl(t *testing.T, opts *k8s.KubectlOptions) string { service := k8s.GetService(t, options, "hello-world-app-service") endpoint := k8s.GetServiceEndpoint(t, options, service, 8080) return fmt.Sprintf("http://%s", endpoint) } The serviceUrl method

$ kubectl config set-credentials … To run the test, first authenticate to a Kubernetes cluster.

Note: Kubernetes is now part of Docker Desktop. Test 100% locally!

$ go test -v -timeout 15m -run TestDockerKubernetes … --- PASS: TestDockerKubernetes (5.69s) Run go test. You can validate your config after every commit in seconds!

Note: tests create and destroy many resources!

Pro tip #1: run tests in completely separate “sandbox” accounts

Tool Clouds Features cloud-nuke AWS (GCP planned) Delete all resources older than a certain date; in a certain region; of a certain type. Janitor Monkey AWS Configurable rules of what to delete. Notify owners of pending deletions. aws-nuke AWS Specify specific AWS accounts and resource types to target. Azure Powershell Azure Includes native commands to delete Resource Groups Pro tip #2: run these tools in cron jobs to clean up left-over resources

Integration tests: test multiple “units” work together.

Integration tests 1. Example: Terraform integration tests 2. Test parallelism 3. Test stages 4. Test retries

infrastructure-as-code-testing-talk └ examples └ hello-world-app └ docker-kubernetes └ proxy-app └ web-service └ modules └ test └ README.md Let’s say you have two Terraform modules you want to test together:

infrastructure-as-code-testing-talk └ examples └ hello-world-app └ docker-kubernetes └ proxy-app └ web-service └ modules └ test └ README.md proxy-app: an app that acts as an HTTP proxy for other web services.

infrastructure-as-code-testing-talk └ examples └ hello-world-app └ docker-kubernetes └ proxy-app └ web-service └ modules └ test └ README.md web-service: a web service that you want proxied.

variable "url_to_proxy" { description = "The URL to proxy." type = string } proxy-app takes in the URL to proxy via an input variable

output "url" { value = module.web_service.url } web-service exposes its URL via an output variable

infrastructure-as-code-testing-talk └ examples └ modules └ test └ hello_world_app_test.go └ docker_kubernetes_test.go └ proxy_app_test.go └ README.md Create proxy_app_test.go

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } The basic test structure

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 1. Configure options for the web service

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 2. Deploy the web service

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 3. Configure options for the proxy app (passing it the web service options)

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 4. Deploy the proxy app

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 5. Validate the proxy app works

func TestProxyApp(t *testing.T) { webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) } 6. At the end of the test, undeploy the proxy app and the web service

func configWebService(t *testing.T) *terraform.Options { return &terraform.Options{ TerraformDir: "../examples/web-service", } } The configWebService method

func configProxyApp(t *testing.T, webServiceOpts *terraform.Options) *terraform.Options { url := terraform.Output(t, webServiceOpts, "url") return &terraform.Options{ TerraformDir: "../examples/proxy-app", Vars: map[string]interface{}{ "url_to_proxy": url, }, } } The configProxyApp method

func configProxyApp(t *testing.T, webServiceOpts *terraform.Options) *terraform.Options { url := terraform.Output(t, webServiceOpts, "url") return &terraform.Options{ TerraformDir: "../examples/proxy-app", Vars: map[string]interface{}{ "url_to_proxy": url, }, } } 1. Read the url output from the web- service module

func configProxyApp(t *testing.T, webServiceOpts *terraform.Options) *terraform.Options { url := terraform.Output(t, webServiceOpts, "url") return &terraform.Options{ TerraformDir: "../examples/proxy-app", Vars: map[string]interface{}{ "url_to_proxy": url, }, } } 2. Pass it in as the url_to_proxy input to the proxy-app module

func validate(t *testing.T, opts *terraform.Options) { url := terraform.Output(t, opts, "url") http_helper.HttpGetWithRetry(t, url, // URL to test 200, // Expected status code `{"text":"Hello, World!"}`, // Expected body 10, // Max retries 3 * time.Second // Time between retries ) } The validate method

$ go test -v -timeout 15m -run TestProxyApp … --- PASS: TestProxyApp (182.44s) Run go test. You’re now testing multiple modules together!

$ go test -v -timeout 15m -run TestProxyApp … --- PASS: TestProxyApp (182.44s) But integration tests can take (many) minutes to run…

Infrastructure tests can take a long time to run

One way to save time: run tests in parallel

func TestProxyApp(t *testing.T) { t.Parallel() // The rest of the test code } func TestHelloWorldAppUnit(t *testing.T) { t.Parallel() // The rest of the test code } Enable test parallelism in Go by adding t.Parallel() as the 1st line of each test.

$ go test -v -timeout 15m === RUN TestHelloWorldApp === RUN TestDockerKubernetes === RUN TestProxyApp Now, if you run go test, all the tests with t.Parallel() will run in parallel

But there’s a gotcha: resource conflicts

resource "aws_iam_role" "role_example" { name = "example-iam-role" } resource "aws_security_group" "sg_example" { name = "security-group-example" } Example: module with hard-coded IAM Role and Security Group names

resource "aws_iam_role" "role_example" { name = "example-iam-role" } resource "aws_security_group" "sg_example" { name = "security-group-example" } If two tests tried to deploy this module in parallel, the names would conflict!

Key takeaway: you must namespace all your resources

resource "aws_iam_role" "role_example" { name = var.name } resource "aws_security_group" "sg_example" { name = var.name } Example: use variables in all resource names…

uniqueId := random.UniqueId() return &terraform.Options{ TerraformDir: "../examples/proxy-app", Vars: map[string]interface{}{ "name": fmt.Sprintf("text-proxy-app-%s", uniqueId) }, } At test time, set the variables to a randomized value to avoid conflicts

Consider the structure of the proxy-app integration test:

1. Deploy web-service 2. Deploy proxy-app 3. Validate proxy-app 4. Undeploy proxy-app 5. Undeploy web-service

1. Deploy web-service 2. Deploy proxy-app 3. Validate proxy-app 4. Undeploy proxy-app 5. Undeploy web-service When iterating locally, you sometimes want to re-run just one of these steps.

1. Deploy web-service 2. Deploy proxy-app 3. Validate proxy-app 4. Undeploy proxy-app 5. Undeploy web-service But as the code is written now, you have to run all steps on each test run.

1. Deploy web-service 2. Deploy proxy-app 3. Validate proxy-app 4. Undeploy proxy-app 5. Undeploy web-service And that can add up to a lot of overhead. (~3 min) (~2 min) (~30 seconds) (~1 min) (~2 min)

Key takeaway: break your tests into independent test stages

webServiceOpts := configWebService(t) defer terraform.Destroy(t, webServiceOpts) terraform.InitAndApply(t, webServiceOpts) proxyAppOpts := configProxyApp(t, webServiceOpts) defer terraform.Destroy(t, proxyAppOpts) terraform.InitAndApply(t, proxyAppOpts) validate(t, proxyAppOpts) The original test structure

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) The test structure with test stages

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) 1. RunTestStage is a helper function from Terratest.

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) 2. Wrap each stage of your test with a call to RunTestStage

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) 3. Define each stage in a function (you’ll see this code shortly).

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) 4. Give each stage a unique name

stage := test_structure.RunTestStage defer stage(t, "cleanup_web_service", cleanupWebService) stage(t, "deploy_web_service", deployWebService) defer stage(t, "cleanup_proxy_app", cleanupProxyApp) stage(t, "deploy_proxy_app", deployProxyApp) stage(t, "validate", validate) Any stage foo can be skipped by setting the env var SKIP_foo=true

$ SKIP_cleanup_web_service=true $ SKIP_cleanup_proxy_app=true Example: on the very first test run, skip the cleanup stages.

$ go test -v -timeout 15m -run TestProxyApp Running stage 'deploy_web_service'… Running stage 'deploy_proxy_app'… Running stage 'validate'… Skipping stage 'cleanup_proxy_app'… Skipping stage 'cleanup_web_service'… --- PASS: TestProxyApp (105.73s) That way, after the test finishes, the infrastructure will still be running.

$ SKIP_deploy_web_service=true $ SKIP_deploy_proxy_app=true Now, on the next several test runs, you can skip the deploy stages too.

$ go test -v -timeout 15m -run TestProxyApp Skipping stage 'deploy_web_service’… Skipping stage 'deploy_proxy_app'… Running stage 'validate'… Skipping stage 'cleanup_proxy_app'… Skipping stage 'cleanup_web_service'… --- PASS: TestProxyApp (14.22s) This allows you to iterate on solely the validate stage…

$ go test -v -timeout 15m -run TestProxyApp Skipping stage 'deploy_web_service’… Skipping stage 'deploy_proxy_app'… Running stage 'validate'… Skipping stage 'cleanup_proxy_app'… Skipping stage 'cleanup_web_service'… --- PASS: TestProxyApp (14.22s) Which dramatically speeds up your iteration / feedback cycle!

$ SKIP_validate=true $ unset SKIP_cleanup_web_service $ unset SKIP_cleanup_proxy_app When you’re done iterating, skip validate and re-enable cleanup

$ go test -v -timeout 15m -run TestProxyApp Skipping stage 'deploy_web_service’… Skipping stage 'deploy_proxy_app’… Skipping stage 'validate’… Running stage 'cleanup_proxy_app’… Running stage 'cleanup_web_service'… --- PASS: TestProxyApp (59.61s) This cleans up everything that was left running.

func deployWebService(t *testing.T) { opts := configWebServiceOpts(t) test_structure.SaveTerraformOptions(t, "/tmp", opts) terraform.InitAndApply(t, opts) } func cleanupWebService(t *testing.T) { opts := test_structure.LoadTerraformOptions(t, "/tmp") terraform.Destroy(t, opts) } Note: each time you run test stages via go test, it’s a separate OS process.

func deployWebService(t *testing.T) { opts := configWebServiceOpts(t) test_structure.SaveTerraformOptions(t, "/tmp", opts) terraform.InitAndApply(t, opts) } func cleanupWebService(t *testing.T) { opts := test_structure.LoadTerraformOptions(t, "/tmp") terraform.Destroy(t, opts) } So to pass data between stages, one stage needs to write the data to disk…

func deployWebService(t *testing.T) { opts := configWebServiceOpts(t) test_structure.SaveTerraformOptions(t, "/tmp", opts) terraform.InitAndApply(t, opts) } func cleanupWebService(t *testing.T) { opts := test_structure.LoadTerraformOptions(t, "/tmp") terraform.Destroy(t, opts) } And the other stages need to read that data from disk.

Real infrastructure can fail for intermittent reasons (e.g., bad EC2 instance, Apt downtime, Terraform bug)

To avoid “flaky” tests, add retries for known errors.

&terraform.Options{ TerraformDir: "../examples/proxy-app", RetryableTerraformErrors: map[string]string{ "net/http: TLS handshake timeout": "Terraform bug", }, MaxRetries: 3, TimeBetweenRetries: 3*time.Second, } Example: retry up to 3 times on a known TLS error in Terraform.

End-to-end tests: test your entire infrastructure works together.

How do you test this entire thing?

You could use the same strategy… 1. Deploy all the infrastructure 2. Validate it works (e.g., via HTTP requests, API calls, SSH commands, etc.) 3. Undeploy all the infrastructure

But it’s rare to write end-to- end tests this way. Here’s why:

e2e Tests Test pyramid Integration Tests Unit Tests Static analysis

e2e Tests Integration Tests Unit Tests Static analysis Cost, brittleness, run time

e2e Tests Integration Tests Unit Tests Static analysis 60 – 240+ minutes 5 – 60 minutes 1 – 20 minutes 1 – 60 seconds

e2e Tests Integration Tests Unit Tests Static analysis E2E tests are too slow to be useful 60 – 240+ minutes 5 – 60 minutes 1 – 20 minutes 1 – 60 seconds

Another problem with E2E tests: brittleness.

Assume a single resource (e.g., EC2 instance) has a 1/1000 (0.1%) chance of failure.

Test type # of resources Chance of failure Unit tests 10 1% Integration tests 50 5% End-to-end tests 500+ 40%+ The more resources your tests deploy, the flakier they will be.

Test type # of resources Chance of failure Unit tests 10 1% Integration tests 50 5% End-to-end tests 500+ 40%+ You can work around the failure rate for unit & integration tests with retries

Key takeaway: E2E tests from scratch are too slow and too brittle to be useful

Instead, you can do incremental E2E testing!

module module module module module module module module module module module module module module module 1. Deploy a persistent test environment and leave it running.

module module module module module module module module module module module module module module module 2. Each time you update a module, deploy & validate just that module

module module module module module module module module module module module module module module module 3. Bonus: test your deployment process is zero-downtime too!

Technique Strengths Weaknesses Static analysis 1. Fast 2. Stable 3. No need to deploy real resources 4. Easy to use 1. Very limited in errors you can catch 2. You don’t get much confidence in your code solely from static analysis Unit tests 1. Fast enough (1 – 10 min) 2. Mostly stable (with retry logic) 3. High level of confidence in individual units 1. Need to deploy real resources 2. Requires writing non-trivial code Integration tests 1. Mostly stable (with retry logic) 2. High level of confidence in multiple units working together 1. Need to deploy real resources 2. Requires writing non-trivial code 3. Slow (10 – 30 min) End-to-end tests 1. Build confidence in your entire architecture 1. Need to deploy real resources 2. Requires writing non-trivial code 3. Very slow (60 min – 240+ min)* 4. Can be brittle (even with retry logic)*

All of them! They all catch different types of bugs.

e2e Tests Keep in mind the test pyramid Integration Tests Unit Tests Static analysis

e2e Tests Lots of unit tests + static analysis Integration Tests Unit Tests Static analysis

e2e Tests Fewer integration tests Integration Tests Unit Tests Static analysis

e2e Tests A handful of high-value e2e tests Integration Tests Unit Tests Static analysis

Infrastructure code without tests is scary

Fight the fear & build confidence in your code with automated tests

How to test infrastructure code: automated testing for Terraform, Kubernetes, Docker, Packer and more

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