Rails fragment cache testing with RSpec

Question

I feel like this is a not-so-much documented topic, at least I\'ve had a lot of trouble finding our about the best practices here.

I\'m fragment caching in the view usin

Answer 1

I use view specs to test cache expiration in views:

describe Expire::Employee, type: :view, caching: true do

  def hour_ago
    Timecop.travel(1.hour.ago) { yield }
  end

  def text_of(css, _in:)
    Nokogiri::HTML(_in).css(css).text
  end

  let(:employee) { hour_ago { create :employee } }

  def render_employees
    assign(:employees, [employee.reload])
    render(template: 'employees/index.html.erb')
  end
  alias_method :employees_list, :render_employees

  context "when an employee's position gets changed" do
    let(:position) { create :position, employee: employee }
    before { hour_ago { position.update!(name: 'Old name') } }
    let(:update_position) { position.update!(name: 'New name') }

    it "should expire the employee's cache" do
      expect { update_position }
        .to change { text_of('.positions', _in: employees_list) }
        .from(/Old name/).to(/New name/)
    end
  end

  # similar spec case for home base assignment
end

where

• Timecop gem is used to travel in time to make sure that cache key timestamps are different for different cache versions of employee
• Nokogiri gem is used to extract employee position's text from the rendered view

Note that I tagged this spec with caching: true. It enables caching before each test case and disables after it:

config.before(:each, caching: true) do
  controller.perform_caching = true
end
config.after(:each, caching: true) do
  controller.perform_caching = false
end

And you might want to add an example that checks that an employee is being actually cached

describe Expire::Employee, type: :view, caching: true do
  context 'with an uncached employee' do
    it 'should cache the employee' do
      expect_any_instance_of(Employee)
        .to receive(:current_positions).once

      2.times { render_employees }
    end
  end

  # other spec cases
end