docker-tdd

TDD and Docker with Serverspec

TDD is a software-development concept. Here we are demonstrating how some aspects of TDD can be adapted for use in Dockerfile development.

• This example demonstrates using some aspects of Test-Driven Development to develop an example Dockerfile.
• Each subdirectory here will give you a step-by-step understanding of how our Dockerized application evolves.

About our Application

• We are creating a Dockerized version of a Spring-Boot Java app - petclinic.
• A binary JAR of this has already been compiled and uploaded here: spring-petclinic-1.5.1.jar

How To Use

Prerequisites

1. A Linux system with the ability to run Ruby, Gems and Bundler is required.
2. Docker 17.05-ce or greater should be installed.
3. A basic knowledge of Ruby, Rubygems, Gemfiles and Bundler is advised.
4. Understanding of the Docker API for Ruby is advised.

Step 1. Create the directory structure.

• First we create the stub files and folders necessary.
• See step-1 directory for details.

Step 2. Create Failing Tests.

• Next, we flesh out the specs (or "behavior" if you will) of our Docker image.
• See step-2 directory for detail.

Step 3. Create the Dockerfile and Make Tests Pass.

• Next we flesh out our Dockerfile so as to fulfil the specs.
• After incrementally filling out our Dockerfile we execute the spec each time.
• See step-3 directory.

Step 4. Loop: Implement Dockerfile, Make Tests Pass, Refactor!

• Continue implementing the rest of the tests.
• Watch the tests fail, implement your Dockerfile and rerun the tests until they pass.
• Refactor as necessary.
• See step-4 directory.

References

1. Serverspec
2. This gist
3. Rspec: creating pending examples
4. Guidelines for writing RSpec Tests
5. The ServerSpec documentation
6. Docker API for Ruby
7. Existing articles on TDD and Docker: 1, 2, 3