Once

The :once record mode will:

• Replay previously recorded interactions.

• Record new interactions if there is no cassette file.

• Cause an error to be raised for new requests if there is a cassette file.

  It is similar to the :new_episodes record mode, but will prevent new, unexpected requests from being made (i.e. because the request URI changed or whatever).

  :once is the default record mode, used when you do not set one.

Background ()

Given a file named "setup.rb" with:

$server = start_sinatra_app do
  get('/') { 'Hello' }
end

require 'vcr'

VCR.configure do |c|
  c.hook_into                :webmock
  c.cassette_library_dir     = 'cassettes'
end

And a previously recorded cassette file "cassettes/example.yml" with:

--- 
http_interactions: 
- request: 
    method: get
    uri: http://example.com/foo
    body: 
      encoding: UTF-8
      string: ""
    headers: {}
  response: 
    status: 
      code: 200
      message: OK
    headers: 
      Content-Length: 
      - "20"
    body: 
      encoding: UTF-8
      string: example.com response
    http_version: "1.1"
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
recorded_with: VCR 2.0.0

Previously recorded responses are replayed

Given a file named "replay_recorded_response.rb" with:

require 'setup'

VCR.use_cassette('example', :record => :once) do
  response = Net::HTTP.get_response('example.com', '/foo')
  puts "Response: #{response.body}"
end

When I run ruby replay_recorded_response.rb

Then it should pass with "Response: example.com response".

New requests result in an error when the cassette file exists

Given a file named "error_for_new_requests_when_cassette_exists.rb" with:

require 'setup'

VCR.use_cassette('example', :record => :once) do
  response = Net::HTTP.get_response('localhost', '/', $server.port)
  puts "Response: #{response.body}"
end

When I run ruby error_for_new_requests_when_cassette_exists.rb

Then it should fail with "An HTTP request has been made that VCR does not know how to handle".

New requests get recorded when there is no cassette file

Given a file named "record_new_requests.rb" with:

require 'setup'

VCR.use_cassette('example', :record => :once) do
  response = Net::HTTP.get_response('localhost', '/', $server.port)
  puts "Response: #{response.body}"
end

When I remove the file "cassettes/example.yml"

And I run ruby record_new_requests.rb

Then it should pass with "Response: Hello"

And the file "cassettes/example.yml" should contain "Hello".