Add have_cacheable_headers matcher for responses (#31727)

spec/support/examples/cache.rb

@@ -1,14 +0,0 @@
-# frozen_string_literal: true
-
-shared_examples 'cacheable response' do |expects_vary: false|
-  it 'sets correct cache and vary headers and does not set cookies or session', :aggregate_failures do
-    expect(response.cookies).to be_empty
-    expect(response.headers['Set-Cookies']).to be_nil
-
-    expect(session).to be_empty
-
-    expect(response.headers['Vary']).to include(expects_vary) if expects_vary
-
-    expect(response.headers['Cache-Control']).to include('public')
-  end
-end

spec/support/matchers/cacheable_response.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+RSpec::Matchers.define :have_cacheable_headers do
+  match do |response|
+    @response = response
+
+    @errors = [].tap do |errors|
+      errors << check_cookies
+      errors << check_cookie_headers
+      errors << check_session
+      errors << check_cache_control
+      errors << check_vary if @expected_vary.present?
+    end
+
+    @errors.compact.empty?
+  end
+
+  chain :with_vary do |string|
+    @expected_vary = string
+  end
+
+  failure_message do
+    <<~ERROR
+      Expected that the response would be cacheable but it was not:
+        - #{@errors.compact.join("\n  - ")}
+    ERROR
+  end
+
+  def check_vary
+    puts @expected_vary
+    pp @response.headers
+    "Response `Vary` header does not contain `#{@expected_vary}`" unless @response.headers['Vary'].include?(@expected_vary)
+  end
+
+  def check_cookies
+    'Reponse cookies are present' unless @response.cookies.empty?
+  end
+
+  def check_cookie_headers
+    'Response `Set-Cookies` headers are present' if @response.headers['Set-Cookies'].present?
+  end
+
+  def check_session
+    'The session is not empty' unless session.empty?
+  end
+
+  def check_cache_control
+    'The `Cache-Control` header does not contain `public`' unless @response.headers['Cache-Control'].include?('public')
+  end
+end