AmiSpec

Acceptance testing your AMIs.

AmiSpec is a RubyGem used to launch an Amazon Machine Image (AMI) and run ServerSpecs against it. It wraps around the AWS API and ServerSpec to spin up, test and tear down instances.

Project Goals

1. To decouple the building of AMIs from testing them. Other approaches to this problem involve copying ServerSpec tests to an EC2 instance before it's converted to an AMI and running the tests there. The problem with this approach is:

• It does not test the instance in the state it will be in when it's actually in production.
• It does makes it harder to replace the AMI builder software (i.e. Packer).
• The software required to test the AMI must exist in the AMI.

2. To run tests as fast as possible; this approach is slightly slower than the alternative listed above (about 1-2 minutes), but should not be onerous.

Installation

System-wide: gem install ami-spec

With bundler:

Add gem 'ami-spec' to your Gemfile. Run bundle install

CLI Usage

$ bundle exec ami_spec --help
Options:
  -r, --role=<s>                    The role to test, this should map to a directory in the spec folder
  -a, --ami=<s>                     The ami ID to run tests against
  -o, --role-ami-file=<s>           A file containing comma separated roles and amis. i.e.
                                    web_server,ami-id.
  -s, --specs=<s>                   The directory to find ServerSpecs
  -u, --subnet-id=<s>               The subnet to start the instance in
  -k, --key-name=<s>                The SSH key name to assign to instances
  -e, --key-file=<s>                The SSH private key file associated to the key_name
  -h, --ssh-user=<s>                The user to ssh to the instance as
  -w, --aws-region=<s>              The AWS region, defaults to AWS_DEFAULT_REGION environment variable
  -i, --aws-instance-type=<s>       The ec2 instance type, defaults to t2.micro (default: t2.micro)
  -c, --aws-security-groups=<s+>    Security groups to associate to the launched instances. May be specified
                                    multiple times
  -p, --aws-public-ip               Launch instances with a public IP
  -t, --ssh-retries=<i>             The number of times we should try sshing to the ec2 instance before
                                    giving up. Defaults to 30 (default: 30)
  -d, --debug                       Don't terminate instances on exit
  -l, --help                        Show this message
$  bundle exec ami_spec \
--role web_server \
--ami ami-12345678 \
--subnet-id subnet-abcdefgh \
--key-name ec2-key-pair \
--key-file ~/.ssh/ec2-key-pair.pem \
--ssh-user ubuntu \
--specs ./my_project/spec

AmiSpec will launch an EC2 instance from the given AMI (--ami), in a subnet (--subnet-id) with a key-pair (--key-name) and try to SSH to it (--ssh-user and --key-file). When the instances becomes reachable it will run all Specs inside the role spec directory (--role i.e. my_project/spec/web_server).

Alternative to the --ami and --role variables, a file of comma separated roles and AMIs (ROLE,AMI\n) can be supplied to --role-ami-file.

Known caveats

RSpec conditions in examples

ServerSpecs advanced tips provides a mechanism to conditionally apply tests based on server information.

describe file('/usr/lib64'), :if => os[:arch] == 'x86_64' do
  it { should be_directory }
end

If these are used in shared examples, say loaded via a rspec helper, this doesn't work with AmiSpec, because the evaluation of os[:arch] == 'x86_64' is done when the spec is loaded not at run time.

Working around this is tricky. We need to move the evaluation of os[:arch] to runtime not load time. Since RSpec example metadata can only be a bool, string or symbol we set a metadata key of :os_arch to the value we expect:

describe file('/usr/lib64'), :os_arch => 'x86_64' do
  it { should be_directory }
end

We then have to set an RSpec exclusion of examples where the architecture does not match the host under test's architecture. This can be done in the spec_helper with a lambda function that tests this:

RSpec.configure do |c|
  c.filter_run_excluding :os_arch => lambda { |arch| arch if os[:arch] != arch }
end

We are exluding any example with the metadata key :os_arch where the value does not match our architecture. Similar examples can be included for os family etc.

Development Status

Active and ready for Production

Contributing

For bug fixes, documentation changes, and small features:

1. Fork it ( https://github.com/envato/ami-spec/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Maintainers

Patrick Robinson (@nemski)

License

AmiSpec uses the MIT license. See LICENSE.txt