rspec_delegate_matcher.rb

delegate.rb

# frozen_string_literal: true

RSpec::Matchers.define :delegate do |method|
  match do |delegator|
    @method = @prefix ? :"#{@to}_#{method}" : method
    @delegator = delegator
    begin
      @delegator.send(@to)
    rescue NoMethodError
      raise "#{@delegator} does not respond to #{@to}!"
    end

    allow(@delegator).to receive(@to).and_return double('receiver')
    allow(@delegator.send(@to)).to receive(method).and_return(:called)
    @delegator.send(@method) == :called
  end

  description do
    "delegate :#{@method} to its #{@to}#{@prefix ? ' with prefix' : ''}"
  end

  failure_message do |_text|
    "expected #{@delegator} to delegate :#{@method} to its #{@to}#{@prefix ? ' with prefix' : ''}"
  end

  failure_message_when_negated do |_text|
    "expected #{@delegator} not to delegate :#{@method} to its #{@to}#{@prefix ? ' with prefix' : ''}"
  end

  chain(:to) { |receiver| @to = receiver }
  chain(:with_prefix) { @prefix = true }
end