Facebook API: error 400 when posting with test user, but works with administrator - facebook

Question

I have facebook integrated on my login page, and now I'm trying to call a build-in action: books.rates using a Test App.
My app gets a valid access_token, and creates new feed items without problems. But when I'm tryng to make a books.rates API call, only works if the logged user is a real person (in my tests is me, also the App administrator), and fails allways with Error 400 when I try to rate a book with a Test User.
In both cases, the code is the same (only access_token and userid changes) and has "publish_actions" premission enabled. I think I'm missing something on Test App configuration, but I'm really lost right now.
Thanks!
Update 1
This is the code that makes the action. It's a test code so its very basic
Dictionary<string, string> postInfo = new Dictionary<string, string>();
postInfo["book"] = "http://www.whakoom.com/comics/6jMl7/52/4";
postInfo["rating:value"] = "4";
postInfo["rating:scale"] = "5";
postInfo["fb:explicitly_shared"] = "true";
string graphUrl = string.Format("https://graph.facebook.com/v2.1/{0}/books.rates?access_token={1}", FbUserID, FbAccessToken);
string fbResp = PostPageContent(graphUrl, postInfo);
private static string PostPageContent(string url, Dictionary<string,string> postData)
{
string postInfo = string.Empty;
foreach(string key in postData.Keys)
{
if (postInfo.Length > 0)
postInfo += "&";
postInfo += string.Format("{0}={1}", HttpContext.Current.Server.UrlEncode(key), HttpContext.Current.Server.UrlEncode(postData[key]));
}
var request = WebRequest.Create(url);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = postInfo.Length;
StreamWriter streamOut = new StreamWriter(request.GetRequestStream(), System.Text.Encoding.ASCII);
streamOut.Write(postInfo);
streamOut.Close();
string retValue = string.Empty;
WebResponse response = request.GetResponse();
var reader = new StreamReader(response.GetResponseStream());
retValue = reader.ReadToEnd();
reader.Close();
return retValue;

Answer 1

It seems that Test App with Test Users is unable to make books.rates calls until the main App is approved. The same api calls targeting a real App with a Test User works without problems.