Assign a Javascript function to AjaxOptions OnSuccess property raise an error - ASP.NET MVC

I'm using the Ajax.ActionLink helper to generate a link to delete a record. This is the code:

Ajax.ActionLink("Delete Image", "DeleteImage", new { id = item.Id },
                                               new AjaxOptions { HttpMethod = "Delete", OnSuccess = "Test()" } )

I'm assign a Javascript function (Test()) to the OnSucess property because I want to do some JQuery stuff, but when I click the Delete link this error message is raised

Microsoft JScript runtime error: 'b' is null or not an object

in the MicrosoftAjax.js file (Line 5, Column 62099). If I remove the OnSuccess property, everything works fine (even if the Test() function is empty, the same error is raised). Thanks for your help!