Tests for meta_tags

commit audit trail:
alphagov/government-frontend@76e9bd2#diff-6048e9f535fbd535b1c38ab5e387e5c6e0a485d411e9edbbbce9b111b40c25b7
(We have not copied the no-image tags yet, as they are not relevant for the
take_part document type. We will bring in when a document type without images
is ported over)

spec/system/meta_tags_spec.rb

@@ -0,0 +1,45 @@
+RSpec.describe "Meta Tags" do
+  before do
+    case_study = GovukSchemas::RandomExample.for_schema(frontend_schema: "take_part") do |random|
+      random.merge!(
+        "title" => "Zhe title",
+        "withdrawn_notice" => {},
+      )
+      random["links"]["available_translations"] = []
+      random
+    end
+
+    stub_content_store_has_item("/government/get-involved/take-part/some-page", case_study.to_json)
+  end
+
+  it "renders the correct meta tags for pages" do
+    visit "/government/get-involved/take-part/some-page"
+
+    expect(page).to have_css("meta[property='og:title'][content='Zhe title']", visible: false)
+  end
+
+  context "for pages with images" do
+    before do
+      case_study = GovukSchemas::RandomExample.for_schema(frontend_schema: "take_part") do |random|
+        random["details"] = random["details"].merge(
+          "image" => {
+            "url" => "https://example.org/image.jpg",
+            "alt_text" => "An accessible alt text",
+          },
+        )
+        random["links"]["available_translations"] = []
+        random
+      end
+
+      stub_content_store_has_item("/government/get-involved/take-part/some-page", case_study.to_json)
+    end
+
+    it "renders image tags" do
+      visit "/government/get-involved/take-part/some-page"
+
+      expect(page).to have_css("meta[name='twitter:card'][content='summary_large_image']", visible: false)
+      expect(page).to have_css("meta[name='twitter:image'][content='https://example.org/image.jpg']", visible: false)
+      expect(page).to have_css("meta[property='og:image'][content='https://example.org/image.jpg']", visible: false)
+    end
+  end
+end