Testing PORO view models with view_context injected

icon_tag.rb

class IconTag
  def initialize(helper:, icon:, project_id:, task_type:, tenant:)
    @helper = helper
    @icon = icon
    @project_id = project_id
    @task_type = task_type
    @tenant = tenant
  end

  def tag
    helper.image_tag(source, alt: description, width: "70")
  end

  private

  attr_reader :helper, :icon, :project_id, :task_type, :tenant

  def source
    if icon.nil?
      "kokoro/themes/#{tenant}/slices/tasks/#{task_type}.png"
    else
      helper.project_asset_path(project_id, icon)
    end
  end

  def description
    if icon.nil?
      "#{task_type.capitalize} Task"
    else
      File.basename(icon, File.extname(icon)).titleize
    end
  end
end

task_decorator.rb

class TaskDecorator < SimpleDelegator
  def initialize(task:, view_context:)
    super(task)
    @view_context = view_context
  end

  def icon_tag
    IconTag.new(
      helper:     view_context,
      icon:       icon,
      project_id: project_id,
      task_type:  type,
      tenant:     view_context.tenant_name
    ).tag
  end
end

task_decorator_spec.rb

RSpec.describe TaskDecorator do
  describe "#icon_tag" do
    context "with no icon set" do
      it "returns an image element for the given Task type" do
        task = double("task", icon: nil, type: "survey")
        view_context = double(
          "view_context",
          tenant_name: "crowdlab",
          params: {},
          image_tag: nil
        )
        decorator = create_decorator(task: task, view_context: view_context)

        decorator.icon_tag

        expected_source = "kokoro/themes/crowdlab/slices/tasks/survey.png"
        expect(view_context)
          .to have_received(:image_tag)
          .with(expected_source, alt: "Survey Task", width: "70")
      end
    end

    context "with an icon set" do
      it "returns an image element" do
        icon = "task_icon.png"
        task = double("task", icon: icon, type: "survey")
        project_id = "1"
        expected_source = "/projects/1/assets/#{icon}"
        view_context = double(
          "view_context",
          tenant_name: "crowdlab",
          params: { project_id: project_id },
          image_tag: nil,
          project_asset_path: expected_source
        )
        decorator = create_decorator(task: task, view_context: view_context)

        decorator.icon_tag
        
        # Example using Capybara to integration test instead:
        # markup = Capybara.string(decorator.icon_tag)
        # expect(markup).to have_css("img[alt='Task Icon']")
        # expect(markup).to have_css("img[width='70']")
        # expect(markup).to have_css("img[src='#{expected_source}']")

        expect(view_context)
          .to have_received(:image_tag)
          .with(expected_source, alt: "Task Icon", width: "70")
        expect(view_context)
          .to have_received(:project_asset_path)
          .with(project_id, icon)
      end
    end
  end
end