Render a different variant in rails

application_helper.rb

module ApplicationHelper
  def with_variant(new_variant, &block)
    old_variants = lookup_context.variants
    begin
      lookup_context.variants = [new_variant]
      return block.call
    ensure
      lookup_context.variants = old_variants
    end
  end
end

# usage: with_variant(:another) { render partial: 'another/partial' }

variants.rb

# spec/support/variants.rb
# `use_variant :another` on the exapmle or within a test
module RailsVariantsMacros
  extend ActiveSupport::Concern

  def use_variant(new_variant)
    view.lookup_context.variants = [new_variant]
  end

  module ClassMethods
    def use_variant(new_variant)
      before { use_variant(new_variant) }
    end
  end
end

RSpec.configure do |config|
  config.include(RailsVariantsMacros, type: :view)
end