Add tests for the different runner errors

spec/factories/runner.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+# This factory does not request the runner management as the id is already provided.
+FactoryBot.define do
+  factory :runner do
+    runner_id { 'test-runner-id' }
+    association :execution_environment, factory: :ruby
+    association :user, factory: :external_user
+    waiting_time { 1.0 }
+  end
+end