VCR: Better Binary Serializer

What

This gem is a VCR serializer which persists any binary data in the HTTP request or response bodies outside the cassette.

Why

• Keeps the cassettes human readable
• You can git diff the cassette more easily (and git won't diff the binary data stored elsewhere)
• Github won't collapse the diffs for cassettes in PRs (the default for large files)

You can read more about this gem in the following blog post.

How

Add the gem to your Gemfile and bundle install:

group :test do
  gem "vcr_better_binary"
end

Configure VCR to use the serializer:

# spec/support/vcr.rb (or wherever you configure VCR)

VCR.configure do |config|
  config.cassette_serializers[:better_binary] = VcrBetterBinary::Serializer.new
  config.default_cassette_options = { serialize_with: :better_binary } # or specify inline in 'VCR.use_cassette'
end

When you re-record or delete a cassette there may be stale references leftover in the storage directory.

Add a hook after all your tests have run to prevent unused data from building up:

RSpec.configure do |config|
  config.after(:suite) do
    VcrBetterBinary::Serializer.new.prune_bin_data
  end
end

And you're set!

The end-result

When you record requests with binary data the resulting cassette will look similar to this:

# Abridged example
http_interactions:
- request:
    method: post
    uri: https://example.com/upload
    body:
      encoding: ASCII-8BIT
      bin_key: lymom-vudim-vunek-mobad-fepak-taset-zosyl-zuhaf-setag
  response:
    status:
      code: 200
      message: OK
    body:
      encoding: ASCII-8BIT
      bin_key: xohog-badok-paneg-memek-tahum-degab-kasip-pefik-colol

And the following files will have been persisted:

spec/fixtures/vcr_cassettes
├── my-cassette.yml
└── bin_data
    ├── lymom-vudim-vunek-mobad-fepak-taset-zosyl-zuhaf-setag
    └── xohog-badok-paneg-memek-tahum-degab-kasip-pefik-colol

All remaining VCR functionality will operate as normal; the only adjustment is the storage of binary data.

Advanced configuration

You can adjust the underlying serializer to save your cassettes in different formats, e.g:

# JSON cassettes
VcrBetterBinary::Serializer.new(base_serializer: VCR::Cassette::Serializers::JSON)