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🟡 Intermediate: The Modular Metropolis#

After fixing the Foundation Stones, CloudHaven is thriving! The city has grown to three districts, and the Guild decided to refactor the infrastructure into reusable modules. A senior engineer started the work using Test-Driven Development - writing tests first, then implementing. But they were called away before finishing, leaving behind working tests... and buggy code that doesn't match them. Your mission: fix the bugs, complete the integration test, and deploy the infrastructure.

⏰ Deadline#

Wednesday, 4 February 2026 at 23:59 CET

ℹī¸ You can still complete the challenge after this date, but points will only be awarded for submissions before the deadline.

đŸ’Ŧ Join the discussion#

Share your solutions and questions in the challenge thread in the Open Ecosystem Community.

đŸŽ¯ Objective#

By the end of this level, you should have:

  • All tests of the districts module pass
  • A completed integration test that applies infrastructure against the mock GCP API to verify end-to-end functionality
  • Three districts deployed with correctly configured infrastructure (vaults and ledgers)

ℹī¸ Important: The tests are correct - they define the expected behavior. Your job is to fix the implementation to match what the tests expect. Don't modify existing tests unless a comment tells you to; let the tests guide your fixes.

🧠 What You'll Learn#

  • OpenTofu module structure & testing with tofu test
  • Test-Driven Development (TDD) workflow
  • Input validation
  • How to use the moved block for refactoring infrastructure

🧰 Toolbox#

Your Codespace comes pre-configured with the following tools to help you solve the challenge:

  • tofu: The OpenTofu CLI for infrastructure provisioning
  • gcp-api-mock: A mock GCP API running locally to simulate cloud resources without real cloud costs

⚠ī¸ Note: The mock API only supports Cloud Storage and Cloud SQL, and only the functions needed for this challenge have been properly tested.

✅ How to Play#

1. Start Your Challenge#

📖 First time? Check out the Getting Started Guide for detailed instructions on forking, starting a Codespace, and waiting for infrastructure setup.

Quick start:

  • Fork the repo
  • Create a Codespace
  • Select "🌆 Adventure 02 | 🟡 Intermediate (The Modular Metropolis)"
  • Wait ~2 minutes for the environment to initialize (Cmd/Ctrl + Shift + P → View Creation Log to view progress)

2. Access the GCP API Mock UI#

  • Open the Ports tab in the bottom panel
  • Find the GCP API Mock row (port 30104) and click the forwarded address
  • This UI lets you explore the mock cloud resources (buckets, databases) created by your OpenTofu configuration

3. Fix the Configuration#

The Guild's senior engineer started refactoring the infrastructure into modules but left before finishing. The tests are failing, and the configuration has bugs.

Review the đŸŽ¯ Objective section to understand what a successful solution looks like.

Where to Look#

All OpenTofu files are located in:

adventures/02-building-cloudhaven/intermediate/
├── main.tf                    # Provider and backend configuration
├── variables.tf               # Input variables
├── districts.tf               # Module calls for each district
├── outputs.tf                 # Infrastructure outputs
├── moved.tf                   # Resource migration blocks
├── modules/district/          # The district module (fix bugs here)
│   ├── main.tf                # Locals and tier configuration
│   ├── variables.tf           # Input validation
│   ├── vault.tf               # Storage bucket resource
│   ├── ledger.tf              # Cloud SQL resource
│   ├── outputs.tf             # Module outputs
│   └── tests/                 # Module tests (read these!)
└── tests/
    └── integration.tftest.hcl # Complete this test

💡 Tip: Run make test to see which tests fail and start fixing bugs.

Apply Your Changes#

After making your fixes:

make test      # Run all tests - should pass
make apply     # Apply infrastructure to mock GCP API

Helpful Documentation#

4. Verify Your Solution#

Once you think you've solved the challenge, it's time to verify!

Run the Smoke Test#

Run the provided smoke test script from the challenge directory:

./smoke-test.sh

If the test passes, your solution is very likely correct! 🎉

Complete Full Verification#

For comprehensive validation and to officially claim completion:

  1. Commit and push your changes to your fork
  2. Manually trigger the verification workflow on GitHub Actions
  3. Share your success with the community

📖 Need detailed verification instructions? Check out the Verification Guide for step-by-step instructions on both smoke tests and GitHub Actions workflows.