Fix Insights displaying JSON on back navigation

- This fix means that Reopening a closed insights tab or navigating back
  to insights will not cause the JSON payload to be displayed

changelogs/unreleased/11821-insights-back-json-fix.yml

+---
+title: Fix Insights displaying JSON on back navigation
+merge_request: 25801
+author:
+type: fixed

ee/app/views/groups/insights/show.html.haml

 - @no_container = true
 
-= render('shared/insights', endpoint: group_insights_path(@group), query_endpoint: query_group_insights_path(@group))
+= render('shared/insights', endpoint: group_insights_path(@group, format: :json), query_endpoint: query_group_insights_path(@group))

ee/app/views/projects/insights/show.html.haml

 - @no_container = true
 
-= render('shared/insights', endpoint: namespace_project_insights_path(@project.namespace, @project), query_endpoint: query_namespace_project_insights_path(@project.namespace, @project))
+= render('shared/insights', endpoint: namespace_project_insights_path(@project.namespace, @project, format: :json), query_endpoint: query_namespace_project_insights_path(@project.namespace, @project))

ee/spec/support/shared_examples/features/insights_shared_examples.rb

@@ -3,7 +3,7 @@
 RSpec.shared_examples 'Insights page' do
   let_it_be(:user) { create(:user) }
 
-  context 'as a permitted user' do
+  describe 'as a permitted user' do
     before(:context) do
       entity.add_maintainer(user)
     end
@@ -24,26 +24,47 @@ RSpec.shared_examples 'Insights page' do
         expect(page).to have_content('Insights')
       end
 
-      context 'hash fragment navigation', :js do
+      context 'navigation' do
         let(:config) { entity.insights_config }
-        let(:non_default_tab_id) { config.keys.last }
-        let(:non_default_tab_title) { config[non_default_tab_id][:title] }
-        let(:hash_fragment) { "#/#{non_default_tab_id}" }
-        let(:route) { path + hash_fragment }
+        let(:default_tab_id) { config.each_key.first }
+        let(:default_tab_title) { config[default_tab_id][:title] }
+        let(:route) { path }
 
         before do
           visit route
-
           wait_for_requests
         end
 
-        it 'loads the correct page' do
+        it 'by default loads the first page', :js do
+          page.within(".insights-container") do
+            expect(page).to have_content(default_tab_title)
+          end
+        end
+
+        context 'hash fragment navigation' do
+          let(:non_default_tab_id) { config.keys.last }
+          let(:non_default_tab_title) { config[non_default_tab_id][:title] }
+          let(:hash_fragment) { "#/#{non_default_tab_id}" }
+          let(:route) { path + hash_fragment }
+
+          it 'loads the correct page', :js do
             page.within(".insights-container") do
               expect(page).to have_content(non_default_tab_title)
             end
           end
         end
 
+        it 'displays correctly when navigating back to insights', :js do
+          visit root_path
+
+          page.evaluate_script('window.history.back()')
+
+          page.within(".insights-container") do
+            expect(page).to have_content(default_tab_title)
+          end
+        end
+      end
+
       context 'when the feature flag is disabled globally' do
         before do
           stub_feature_flags(insights: false)