public void GetAcrValues_should_return_snapshot_of_values()
    {
        var request = new ValidatedAuthorizeRequest()
        {
            Raw = new System.Collections.Specialized.NameValueCollection()
        };

        request.AuthenticationContextReferenceClasses.Add("a");
        request.AuthenticationContextReferenceClasses.Add("b");
        request.AuthenticationContextReferenceClasses.Add("c");

        var acrs = request.GetAcrValues();

        foreach (var acr in acrs)
        {
            request.RemoveAcrValue(acr);
        }
    }