c# Unit Testing for Generic method

I have to test the below generic method which is internal class of another assembly.

internal class JsonSerializationUtility
{ 
  public static string SerializeJson<T>(T obj) 
  { 
    string jsonFormattedString = string.Empty; 
    try { 
        MemoryStream memStreamObj = new MemoryStream();
        DataContractJsonSerializer jsonSerObj = new DataContractJsonSerializer(typeof(T)); 
        jsonSerObj.WriteObject(memStreamObj, obj); 
        memStreamObj.Position = 0; StreamReader sr = new StreamReader(memStreamObj); 
        jsonFormattedString = sr.ReadToEnd(); 
    }
    catch (Exception ex) { 
        Log.Error("Exception details: ", ex); 
    } 
  return jsonFormattedString; 
  }
}

and i have tried in this way:

[TestMethod]
public void SerializeJson() 
{ 
    PrivateType privateObj = new PrivateType(typeof(JsonSerializationUtility)); 
    string input= "WorldCup2015"; 
    string output = privateObj.InvokeStatic("SerializeJson<objectType>", input).ToString(); 
    Assert.IsNotNull(output); 
}

But i am getting the missing method reference. Can anyone suggest how should have to test for Generic method.

I had done same procedure of writing test code for simple static method, but unable for generic method.