Some custom rspec matchers for inspecting json responses

matchers.rb

require 'rspec/expectations'

# expect(response).to be_json_success
RSpec::Matchers.define :be_json_success do |_expected|
  match do |actual|
    actual.status == 200 && actual.content_type.match("application/json")
  end

  failure_message do |actual|
    "expected status: 200, content_type: 'application/json', got status: #{actual.status}, content_type: '#{actual.content_type}'"
  end
end

# expect(response).to have_json_status(:created)
RSpec::Matchers.define :have_json_status do |expected|
  def numeric_status(status)
    case status
    when Symbol
      Rack::Utils::SYMBOL_TO_STATUS_CODE[status]
    else
      status
    end
  end

  match do |actual|
    actual.status == numeric_status(expected) && actual.content_type.match("application/json")
  end

  failure_message do |actual|
    "expected status: #{numeric_status(expected)}, content_type: 'application/json', got status: #{actual.status}, content_type: '#{actual.content_type}'"
  end
end

# expect(response).to have_json_keys(%w[id created_at updated_at])
RSpec::Matchers.define :have_json_keys do |expected|
  def parse(response)
    JSON.parse(response.body)
  end

  def formatter(array)
    "[ #{array.sort.join(', ')} ]"
  end

  # if key order is important I recommend an explicit test
  match do |actual|
    parse(actual).keys.sort == expected.sort
  end

  failure_message do |actual|
    actual_keys = parse(actual).keys

    difference = actual_keys.union(expected) - actual_keys.intersection(expected)

    <<~MESSAGE
      expected the following JSON keys:
      #{formatter(expected)}

      got:
      #{formatter(actual_keys)}"

      symmetric difference:
      #{formatter(difference)}
    MESSAGE
  end
end