Great question! Unfortunately, VCR doesn't ship with an out-of-the-box request matcher that ignores specific attributes in the request body, but it's straightforward to build a custom one (or use a handy workaround) to solve your problem. Let's break down your options:

1. Custom Request Matcher (Flexible & Targeted) #

This is the most direct solution: define a custom request matcher that parses the request body, strips out the dynamic attribute (like id), and compares the cleaned bodies.

Step 1: Define the Matcher #

Add this to your VCR configuration file (typically spec/spec_helper.rb or spec/support/vcr.rb):

VCR.configure do |config|
  # Your existing VCR config (like cassette directory, etc.) goes here

  # Define a matcher that ignores the 'id' attribute in JSON bodies
  config.define_request_matcher :body_without_id do |request1, request2|
    # Parse JSON bodies (adjust this if your requests use form data or another format)
    body1 = JSON.parse(request1.body)
    body2 = JSON.parse(request2.body)

    # Remove the 'id' attribute from both bodies
    cleaned_body1 = body1.except('id')
    cleaned_body2 = body2.except('id')

    # Compare the cleaned bodies
    cleaned_body1 == cleaned_body2
  end
end

Step 2: Use the Matcher #

When setting up your VCR cassette, specify this matcher alongside the standard :method and :uri matchers:

VCR.use_cassette("your_cassette_name", match_requests_on: [:method, :uri, :body_without_id]) do
  # Your test code that makes the API request goes here
end

Adjustment for Non-JSON Bodies

If your requests use form data instead of JSON, replace the parsing logic with Rack::Utils.parse_nested_query:

config.define_request_matcher :form_body_without_id do |request1, request2|
  body1 = Rack::Utils.parse_nested_query(request1.body)
  body2 = Rack::Utils.parse_nested_query(request2.body)

  cleaned_body1 = body1.except('id')
  cleaned_body2 = body2.except('id')

  cleaned_body1 == cleaned_body2
end

2. Workaround: Use filter_sensitive_data #

If you prefer not to build a custom matcher, you can use VCR's filter_sensitive_data feature to replace dynamic values (like the id) with a static placeholder during recording and playback. This way, both the recorded request and your test's new request will use the same placeholder, making them match.

Add this to your VCR config:

VCR.configure do |config|
  # Replace any numeric ID in the request body with a placeholder
  config.filter_sensitive_data('<REQUEST_ID>') do
    /\d+/ # Matches any sequence of digits (adjust the regex to match your ID format)
  end
end

When you re-record your cassette, the original id will be replaced with <REQUEST_ID>. When your test runs with a new id, VCR will replace that new id with the same placeholder, allowing the request to match the recorded cassette.

Notes for Rails Newcomers #

• Your VCR configuration is usually set up in spec/spec_helper.rb or a dedicated file in spec/support/ (like vcr.rb). Make sure this code runs before your tests execute.
• If you need to ignore multiple attributes, just add them to the except call (e.g., body1.except('id', 'created_at', 'updated_at')).

内容的提问来源于stack exchange，提问作者Daniel Lopez