Grails Troubleshooting error "Only classes and closures can be used for attribute 'value' in @grails.test.mixin.TestFor"

When Unit Testing URL Mappings I get the error Only classes and closures can be used for attribute 'value' in @grails.test.mixin.TestFor. The URL Mapping unit test should be in the default package as stated in the Grails documentation because the URL mapping files named *UrlMappings.groovy are in the default package.