Test dockefile with ruby/docker-api/serverspec

dockerfile_spec.rb

require "serverspec"
require "docker"

package = ['rake', 'pg']

describe "Dockerfile" do
  before(:all) do
    @image = Docker::Image.build_from_dir('.', {'dockerfile'=>'Dockerfile'})
    @image.tag(repo: 'image-test', tag: 'latest').  

    set :os, family: :alpine  # redhat, debian, alpine
    set :backend, :docker
    set :docker_image, @image.id
    set :docker_container_create_options, { 'Entrypoint' => ['bash'] }. # if you see - blah blah OCI runtime
  end
  
  package.each do |p|
    describe package(p) do
      it { should be_installed.by('gem') }
    end
  end

  describe file('/etc/passwd') do
    it { should exist }
  end
end