Check GraphQL feature flag in ministers index

When the `GRAPHQL_FEATURE_FLAG` environment variable or the `graphql`
query param is set, use Publishing API's GraphQL endpoint as the source
of the data for serving the Ministers Index page. Otherwise use the
standard Content Store data source.

app/controllers/ministers_controller.rb

@@ -2,8 +2,15 @@ class MinistersController < ApplicationController
   around_action :switch_locale
 
   def index
-    ministers_index = MinistersIndex.find!(request.path)
-    @presented_ministers = MinistersIndexPresenter.new(ministers_index.content_item.content_item_data)
+    if Features.graphql_feature_enabled? || params.include?(:graphql)
+      ministers_index = Graphql::MinistersIndex.find!(request.path)
+      content_item_data = ministers_index.content_item
+    else
+      ministers_index = MinistersIndex.find!(request.path)
+      content_item_data = ministers_index.content_item.content_item_data
+    end
+
+    @presented_ministers = MinistersIndexPresenter.new(content_item_data)
     setup_content_item_and_navigation_helpers(ministers_index)
   end
 end

spec/features/ministers_spec.rb

@@ -123,24 +123,53 @@
     end
   end
 
-  let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-off") }
+  context "without the graphql feature flag" do
+    let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-off") }
 
-  before do
-    stub_content_store_has_item("/government/ministers", document)
-    visit "/government/ministers"
-  end
+    before do
+      stub_content_store_has_item("/government/ministers", document)
+      visit "/government/ministers"
+    end
 
-  it_behaves_like "ministers index page"
+    it_behaves_like "ministers index page"
 
-  context "during a reshuffle" do
-    let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-on") }
+    context "during a reshuffle" do
+      let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-on") }
+
+      it_behaves_like "ministers index page during a reshuffle"
+    end
 
-    it_behaves_like "ministers index page during a reshuffle"
+    context "during a reshuffle preview" do
+      let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-on-preview") }
+
+      it_behaves_like "ministers index page during a reshuffle preview"
+    end
   end
 
-  context "during a reshuffle preview" do
-    let(:document) { GovukSchemas::Example.find("ministers_index", example_name: "ministers_index-reshuffle-mode-on-preview") }
+  context "with the GraphQL feature flag" do
+    let(:document) { fetch_graphql_fixture("ministers_index-reshuffle-mode-off") }
+
+    before do
+      enable_graphql_feature_flag
+      stub_publishing_api_graphql_query(
+        Graphql::MinistersIndexQuery.new("/government/ministers").query,
+        document,
+      )
+      visit "/government/ministers"
+    end
+
+    it_behaves_like "ministers index page"
 
-    it_behaves_like "ministers index page during a reshuffle preview"
+    context "during a reshuffle" do
+      let(:document) { fetch_graphql_fixture("ministers_index-reshuffle-mode-on") }
+
+      it_behaves_like "ministers index page during a reshuffle"
+    end
+
+    context "during a reshuffle preview" do
+      let(:document) { fetch_graphql_fixture("ministers_index-reshuffle-mode-on-preview") }
+
+      it_behaves_like "ministers index page during a reshuffle preview"
+    end
   end
 end