Structure Testing for Docker Containers

Container Structure Tests (CST) is a tool developed by Google, available under the Apache 2.0 license, designed to validate the contents and configuration of container images, ensuring their reliability before deployment. This tool, although not officially supported by Google, provides predefined tests for various aspects such as file existence, permissions, command outputs, environment variables, and metadata within a container image, corresponding to Dockerfile keywords. The tutorial outlines how to integrate CST into a CI/CD pipeline using a Ruby Kubernetes demo project, demonstrating the setup and execution of command, filesystem, and metadata tests. The integration of CST into the CI/CD process is explained with steps for installing CST, configuring tests, and running them in the pipeline to enhance the reliability of containerized applications. Through this process, CST helps minimize deployment surprises by offering a straightforward method to verify container integrity, making it a valuable tool for developers working with containers in serious projects.