More informative RSpec #be_success matcher with negotiation

be_success_matcher.rb

# spec/rails_helper.rb or spec/spec_helper.rb
# ...
# require custom matchers from the "support" directory:
Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }

# -----

# support/matchers/be_success.rb
RSpec::Matchers.define :be_success do
  match do |actual|
    actual.success?
  end

  failure_message do |actual|
    "expected to be success, but it is not\n\n#{data_for_response(actual)}"
  end

  failure_message_when_negated do |actual|
    "expected that response would not be success, but it is\n\n#{data_for_response(actual)}"
  end

  private

  def data_for_response(response)
    request = response.request

    "Request path: #{request.request_method} #{request.fullpath}\n\n" \
    "Request params: #{prettify_json(request.request_parameters.to_json)}\n\n" \
    "Response status: #{response.status}\n\n" \
    "Response body: #{prettify_json(response.body)}"
  end

  def prettify_json(json)
    JSON.pretty_generate(JSON.parse(json))
  end
end