VCR debug_logger

# log as puts
VCR.configure do |c|
  c.debug_logger = $stderr
end

# log to a file
VCR.configure do |c|
  c.debug_logger = File.open('vcr.log', 'w')
end

Reference

• http://www.rubydoc.info/github/vcr/vcr/VCR%2FConfiguration%3Adebug_logger