AWS::CloudFormation::Init RSpec validation

Overview

A proof of concept using RSpec to validate AWS::CloudFormation::Init configurations.

What it does

Based on documentation here, I have reduced the AWS::CloudFormation::Init configuration to a specification in this Ruby Hash in the RSpec test file:

$types = {
  'packages' => {
    'apt'      => {String => Array},
    'msi'      => {String => String},
    'python'   => {String => Array},
    'rpm'      => {String => String},
    'rubygems' => {String => Array},
    'yum'      => {String => Array},
  },
  'groups' => {
    String => {'gid' => Fixnum},
  },
  'users' => {
    String => {
      'groups'  => Array,
      'uid'     => Fixnum,
      'homeDir' => String,
    },
  },
  'sources' => {String => String},
  'files' => {
    String => {
      'content'   => String,
      'source'    => /^http/,
      'encoding'  => /plain|base64/,
      'group'     => String,
      'owner'     => String,
      'mode'      => Fixnum,
      'authentication' => String,
      'context'        => String,
    },
  },
  'commands' => {
    String => {
      'command'  => String, 
      'env'      => Hash,   
      'cwd'      => String,
      'test'     => String,
      'ignoreErrors'   => Boolean,
      'waitAfterCompletion' => Boolean,
    },
  },
  'services' => {
    /sysvinit|windows/ => {
      String => {
        'ensureRunning' => Boolean,
        'enabled'   => Boolean,
        'files'     => Array,
        'sources'   => Array,
        'packages'  => Array,
        'commands'  => Array,
      },
    },
  },
}

I take this to be a concise specification of all valid AWS::CloudFormation::Init configurations.

The contents of the AWS::CloudFormation::Init is then recursively compared against this structure. Data types and regular expressions in the structure are taken as placeholders for real data and data is validated against these. A few other bits and pieces are also validated.

For more information, everything interesting is in the source code in spec/validate_spec.rb and test_runner.sh.

Dependencies

To run the demo you need:

• Ruby (tested on Ruby 2.1.4)
• Rubygems
• Bundler
• Python
• Virtualenv
• Make

Demo

To run the demo:

▶ make

The test runner will download a bunch of example CloudFormation templates with AWS::CloudFormation::Init blocks and validate them.

Usage

To validate your own CloudFormation template:

• Clone this project and cd to the project root.

• Save your template as cloudformation.yml.

• If necessary, convert it from JSON (look in test_runner.sh to understand how to do that).

• Then:

▶ bundle install
▶ bundle exec rake

Or, just fork this project and use spec/validate_spec.rb in your own project.

Known issues

Use of If conditionals to populate fields within the AWS::CloudFormation::Init config will cause fields to appears as Arrays instead of Booleans etc. For example, here.

License

MIT.