HydratePropertyTest.cs

public class Person
{
    public string Name { get; set; }
    public string Address { get; set; }
}

public class InputModel
{
    public string GroupId { get; set; }
    public Person Person { get; set; }
}

[Test]
public void should_serialize_person_into_person_property()
{
    var inputModel = JsonConvert.DeserializeObject<InputModel>(
        "{ ""Name"":""Tom"", ""Address"":""123 Yada Lane""}");

    inputModel.GroupId.ShouldBeNull();
    inputModel.Person.ShouldNotBeNull();
    inputModel.Person.Name.ShouldEqual("Tom");
    inputModel.Person.Address.ShouldEqual("123 Yada Lane");
}