Use helpers in Capybara tests

form_helper.rb

module FormHelper
  def login_form
    find('#new_session')
  end
end

sign_in_test.rb

class SignInTest < ActionDispatch::IntegrationTest
  include FormHelper
  
  setup do
    @sophie = users(:sophie)
  end
  
  test "sign in with valid credentials" do
    visit sign_in_url
    
    within login_form do
      fill_in "Email", with: @sophie.email
      fill_in "Password", with: 'secret'
      click_button "Sign In"
    end
    
    assert page.has_content?("Signed in as #{@sophie.email}")
  end
end