```ruby
require 'serverspec'
require 'docker'

set :backend, :docker

# Setup Docker URL and certificates if running via a remote Docker Host.
if ENV['DOCKER_HOST']
  docker_host = ENV['DOCKER_HOST'].dup
  if (ENV['DOCKER_TLS_VERIFY'])
    cert_path = File.expand_path ENV['DOCKER_CERT_PATH']
    Docker.options = {
      client_cert: File.join(cert_path, 'cert.pem'),
      client_key: File.join(cert_path, 'key.pem')
    }
    Excon.defaults[:ssl_ca_file] = File.join(cert_path, 'ca.pem')
    docker_host.gsub!(/^tcp/,'https')
  end
  Docker.url = docker_host
end

# Workaround needed for Travis
if ENV['TRAVIS']
  class Docker::Container
    def remove(options={}); end
    alias_method :delete, :remove
  end
  Docker.url = 'unix:///var/run/docker.sock'
end

# Require all local shared files.
Dir["#{File.dirname(__FILE__)}/_shared/**/*.rb"].each do |f|
  require f
end

RSpec.configure do |config|
  config.mock_with :rspec
  config.tty = true
  config.include Helpers
end
```

Adjust for switch to Circle CI.
user
```ruby
require 'serverspec'
require 'docker'

set :backend, :docker

# Setup Docker URL and certificates if running via a remote Docker Host.
if ENV['DOCKER_HOST']
  docker_host = ENV['DOCKER_HOST'].dup
  if (ENV['DOCKER_TLS_VERIFY'])
    cert_path = File.expand_path ENV['DOCKER_CERT_PATH']
    Docker.options = {
      client_cert: File.join(cert_path, 'cert.pem'),
      client_key: File.join(cert_path, 'key.pem')
    }
    Excon.defaults[:ssl_ca_file] = File.join(cert_path, 'ca.pem')
    docker_host.gsub!(/^tcp/,'https')
  end
  Docker.url = docker_host
end

# Workaround needed for Circle CI.
if ENV['CIRCLECI']
  class Docker::Container
    def remove(options={}); end
    alias_method :delete, :remove
  end
  Docker.url = 'unix:///var/run/docker.sock'
end

# Require all local shared files.
Dir["#{File.dirname(__FILE__)}/_shared/**/*.rb"].each do |f|
  require f
end

RSpec.configure do |config|
  config.mock_with :rspec
  config.tty = true
  config.include Helpers
end
```
assistant