public void TestSetByName()
 {
     var wrapper = new BsonDocumentWrapper(new BsonDocument("x", 1));
     Assert.AreEqual(false, wrapper.IsMaterialized);
     wrapper.Set("x", 2);
     Assert.AreEqual(true, wrapper.IsMaterialized);
     Assert.AreEqual(1, wrapper.ElementCount);
     Assert.AreEqual("x", wrapper.GetElement(0).Name);
     Assert.AreEqual(new BsonInt32(2), wrapper[0]);
 }