fails:Kernel#instance_variable_get tries to convert the passed argument to a String using #to_str
fails:Kernel#instance_variable_get returns the value of the passed instance variable that is referred to by the conversion result
fails:Kernel#instance_variable_get raises a NameError when the conversion result does not start with an '@'
fails:Kernel#instance_variable_get when passed Symbol raises a NameError when passed :@ as an instance variable name
fails:Kernel#instance_variable_get when passed Symbol raises a NameError when the passed Symbol is an invalid instance variable name
fails:Kernel#instance_variable_get when passed String raises a NameError when the passed String is an invalid instance variable name
fails:Kernel#instance_variable_get when passed String raises a NameError when passed '@' as an instance variable name
fails:Kernel#instance_variable_get raises a NameError when passed just '@'
