6 Testing

Recall from Chapter 1 that infrastructure as code involves an entire process to push a change to a system. You update scripts or configurations with infrastructure changes, push them to a version control system, and apply the changes in an automated way. However, you can use every module and dependency pattern from chapters 3 and 4 and still have failed changes! How do you catch a failed change before you apply it to production?

You can solve this problem by implementing tests for infrastructure as code. Testing is a process that evaluates whether or not a system works as expected. This chapter reviews some considerations and concepts related to testing infrastructure as code to reduce the rate of change failure and build confidence in infrastructure changes.

Imagine you configure a network switch with a new network segment. You can manually test existing networks by pinging each server on each network and verifying their connectivity. To test if you set up the new network correctly, you create a new server and check if it responds when you connect to it. This manual test takes a few hours for two or three networks.

6.1 The infrastructure testing cycle

6.1.1 Static analysis

6.1.2 Dynamic analysis

6.1.3 Infrastructure testing environments

6.2 Unit tests

6.2.1 Testing infrastructure configuration

6.2.2 Testing domain-specific languages

6.2.3 When should you write unit tests?

6.3 Contract tests

6.4 Integration tests

6.4.1 Testing modules

6.4.2 Testing configuration for environments

6.4.3 Testing challenges

6.5 End-to-end tests

6.6 Other tests

6.7 Choosing tests

6.7.1 Module testing strategy

6.9 Summary