Create matcher for asserting components of ViewComponents have been rendered with arguments or not

have_rendered_component_matcher.rb

# This gist was used to create have_rendered_page_component matcher, because our intention was to
# assure that a specific page_component was being rendered.


# This is overriding the instrumentation of ViewComponent
# to include the parameters that a component might receive when rendering.
# frozen_string_literal: true

require "active_support/notifications"
require "active_support/concern"

module ViewComponent
  module Instrumentation
    def render_in(view_context, &)
      arguments = public_methods(false) & instance_variables.map { |method| method.to_s.delete("@").to_sym }
      parameters = arguments.index_with { |arg| send(arg) }
      ActiveSupport::Notifications.instrument(
        "!render.view_component",
        {
          name: self.class.name,
          identifier: self.class.identifier,
          parameters: parameters
        }
      ) do
        super(view_context, &)
      end
    end
  end
end

# Overriding RenderTemplateMatcher to be able to receive arguments and also in matchers? method to call assert_page_component
module RSpec
  module Rails
    module Matchers
      module RenderTemplate
        class RenderTemplateMatcher
          def with(**arguments)
            @arguments = arguments
            self
          end

          def matches?(*)
            match_check = match_unless_raises ActiveSupport::TestCase::Assertion do
              @scope.assert_page_component expected, @arguments, @message
            end
            check_redirect unless match_check
            match_check
          end
        end
      end
    end
  end
end

# Creating the PageComponentMatcher module
module PageComponentMatcher
  extend ActiveSupport::Concern

  included do
    setup :setup_subscriptions
    teardown :teardown_subscriptions
  end

  def setup_subscriptions
    @_pages = Hash.new(0)
    @_subscribers = []
    @_subscribers << ActiveSupport::Notifications.subscribe("!render.view_component") do |event|
      payload = event.payload

      @_pages[payload[:name]] = payload[:parameters] if payload[:identifier].match?(%r{/pages/(.*)/}) # If you want to test for just components, change this to %r{/components/(.*)/} 
    end
  end

  def teardown_subscriptions
    return unless defined?(@_subscribers)

    @_subscribers.each { |subscriber| ActiveSupport::Notifications.unsubscribe(subscriber) }
  end

  def reset_template_assertion
    @_pages.clear
  end

  def assert_page_component(component, arguments, message = nil)
    response.body
    component_message = message || format(
      "expecting %<expected>s but rendered %<actual>s", expected: component.inspect, actual: @_pages.keys.first
    )
    params_message = format("expecting %<args>s but received %<params>s", args: arguments, params: @_pages.values.first)
    matches_component = @_pages.any? { |component_name, _| component_name == component }
    matches_arguments = arguments.present? ? @_pages.each_value.all?(arguments) : true
    assert matches_component, component_message
    assert matches_arguments, params_message
  end

  def have_rendered_page_component(component, message = nil)
    RSpec::Rails::Matchers::RenderTemplate::RenderTemplateMatcher.new(self, component, message)
  end
end

RSpec.configure do |config|
  config.include PageComponentMatcher, type: :request
end