add test to france connect controller

app/controllers/france_connect_controller.rb

@@ -14,6 +14,8 @@ class FranceConnectController < ApplicationController
   end
 
   def callback
+    return redirect_to new_user_session_path unless params.has_key?(:code)
+
     user_infos = FranceConnectService.retrieve_user_informations(params[:code])
 
     unless user_infos.nil?

spec/controllers/france_connect_controller_spec.rb

@@ -8,5 +8,26 @@ describe FranceConnectController, type: :controller do
       expect(response.status).to eq(302)
     end
   end
+
+  describe '.callback' do
+    context 'when param code is missing' do
+      it 'redirect to login page' do
+        get :callback
+        expect(response).to redirect_to(new_user_session_path)
+      end
+    end
+    context 'when params code is present' do
+      let(:code) { 'plop'}
+      context 'when code is correct' do
+        before do
+          allow(FranceConnectService).to receive(:retrieve_user_informations).and_return(Hashie::Mash.new(email: 'patator@cake.com'))
+        end
+        it 'redirect to login page' do
+          get :callback, code: code
+          expect(response).to redirect_to(controller: 'users/dossiers', action: :index)
+        end
+      end
+    end
+  end
 end