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Project: Vcr 2.0.0

Publisher: VCR

before_playback hook

The before_playback hook is called before a cassette sets up its
stubs for playback.

Your block should accept up to 2 arguments. The first argument will be
the HTTP interaction that is about to be used for play back. The second
argument will be the current cassette.

You can also call #ignore! on the HTTP interaction to prevent VCR
from playing it back.

If you don't your hook to apply to all cassettes, you can use tags for
this purpose. Consider this code:

VCR.configure do |c|
  c.before_playback(:twitter) { ... } # modify the interactions somehow
end

VCR.use_cassette('cassette_1', :tag => :twitter) { ... }
VCR.use_cassette('cassette_2') { ... }

In this example, the hook would apply to the first cassette but not the
second cassette.

Background
Given
a previously recorded cassette file "cassettes/example.yml" with: 
--- 
http_interactions: 
- request: 
    method: get
    uri: http://localhost:7777/
    body: 
      encoding: UTF-8
      string: ""
    headers: {}
  response: 
    status: 
      code: 200
      message: OK
    headers: 
      Content-Type: 
      - text/html;charset=utf-8
      Content-Length: 
      - "20"
    body: 
      encoding: UTF-8
      string: previously recorded response
    http_version: "1.1"
  recorded_at: Tue, 01 Nov 2011 04:58:44 GMT
recorded_with: VCR 2.0.0
Scenarios
  1. Modify played back response
  2. Modify played back response based on the cassette
  3. Prevent playback by ignoring interaction in before_playback hook
  4. Multiple hooks are run in order
  5. Use tagging to apply hooks to only certain cassettes
Modify played back response
Given
a file named "before_playback_example.rb" with: 
require 'vcr'

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

  c.before_playback do |interaction|
    interaction.response.body = 'response from before_playback'
  end
end

VCR.use_cassette('example') do
  response = Net::HTTP.get_response('localhost', '/', 7777)
  puts "Response: #{response.body}"
end
When
I run ruby before_playback_example.rb
Then
it should pass with "Response: response from before_playback"
Modify played back response based on the cassette
Given
a file named "before_playback_example.rb" with: 
require 'vcr'

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

  c.before_playback do |interaction, cassette|
    interaction.response.body = "response for #{cassette.name} cassette"
  end
end

VCR.use_cassette('example') do
  response = Net::HTTP.get_response('localhost', '/', 7777)
  puts "Response: #{response.body}"
end
When
I run ruby before_playback_example.rb
Then
it should pass with "Response: response for example cassette"
Prevent playback by ignoring interaction in before_playback hook
Given
a file named "before_playback_ignore.rb" with: 
start_sinatra_app(:port => 7777) do
  get('/') { "sinatra response" }
end

require 'vcr'

VCR.configure do |c|
  c.hook_into :fakeweb
  c.cassette_library_dir = 'cassettes'
  c.before_playback { |i| i.ignore! }
end

VCR.use_cassette('localhost', :record => :new_episodes) do
  response = Net::HTTP.get_response('localhost', '/', 7777)
  puts "Response: #{response.body}"
end
When
I run ruby before_playback_ignore.rb
Then
it should pass with "Response: sinatra response"
Multiple hooks are run in order
Given
a file named "multiple_hooks.rb" with: 
require 'vcr'

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

  c.before_playback { puts "In before_playback hook 1" }
  c.before_playback { puts "In before_playback hook 2" }
end

VCR.use_cassette('example', :record => :new_episodes) do
  response = Net::HTTP.get_response('localhost', '/', 7777)
  puts "Response: #{response.body}"
end
When
I run ruby multiple_hooks.rb
Then
it should pass with: 
In before_playback hook 1
In before_playback hook 2
Response: previously recorded response
Use tagging to apply hooks to only certain cassettes
Given
a file named "tagged_hooks.rb" with: 
require 'vcr'

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

  c.before_playback(:tag_2) do |i|
    puts "In before_playback hook for tag_2"
  end
end

[:tag_1, :tag_2, nil].each do |tag|
  puts
  puts "Using tag: #{tag.inspect}"

  VCR.use_cassette('example', :record => :new_episodes, :tag => tag) do
    response = Net::HTTP.get_response('localhost', '/', 7777)
    puts "Response: #{response.body}"
  end
end
When
I run ruby tagged_hooks.rb
Then
it should pass with: 
Using tag: :tag_1
Response: previously recorded response

Using tag: :tag_2
In before_playback hook for tag_2
Response: previously recorded response

Using tag: nil
Response: previously recorded response

Last published almost 5 years ago by myronmarston.