Post with Custom Object parameter not getting data

Question

I am using the Post function from the Visual Studio template as seen below, but I've modified it to receive a custom object Testing. When I use Fiddler to Post I am able to step into the code, but both id and name inside of the Testing object are null. Am I misunderstanding something as to why the don't have the values I am passing in through the Request Body?

public void Post([FromBody] Testing value)
{
    var a = value;
}

public class Testing
{
    string id;
    string name;
}