Fix uninitialized constant testing integrations

app/controllers/projects/services_controller.rb

@@ -61,7 +61,7 @@ class Projects::ServicesController < Projects::ApplicationController
       return { error: true, message: _('Validations failed.'), service_response: @service.errors.full_messages.join(','), test_failed: false }
     end
 
-    result = Integrations::Test::ProjectService.new(@service, current_user, params[:event]).execute
+    result = ::Integrations::Test::ProjectService.new(@service, current_user, params[:event]).execute
 
     unless result[:success]
       return { error: true, message: _('Test failed.'), service_response: result[:message].to_s, test_failed: true }

changelogs/unreleased/fix-uninitialized-constant.yml

+---
+title: Fix error message when saving an integration and testing the settings.
+merge_request: 36700
+author:
+type: fixed