Added some Content-Type unit tests

spec/controllers/index_controller_spec.rb

@@ -10,6 +10,10 @@ RSpec.describe(IndexController) do
       expect(last_response).to(be_ok)
     end
 
+    it 'Dashboard is an HTML response' do
+      expect(last_response['Content-Type']).to(include('text/html'))
+    end
+
     it "Dashboard contains 'Game Data' on page (nav bar should be loaded)." do
       expect(last_response.body).to(include('Game Data'))
     end