public void TestGetDocumentId()
        {
#pragma warning disable 618
            var expectedId = new BsonObjectId(ObjectId.GenerateNewId());
            var wrapper    = new BsonDocumentWrapper(new BsonDocument("_id", expectedId));
            Assert.AreEqual(false, wrapper.IsMaterialized);
            object       id;
            Type         idNominalType;
            IIdGenerator idGenerator;
            wrapper.GetDocumentId(out id, out idNominalType, out idGenerator);
            Assert.AreEqual(true, wrapper.IsMaterialized);
            Assert.IsInstanceOf <BsonObjectId>(id);
            Assert.AreEqual(expectedId, id);
            Assert.AreSame(typeof(BsonValue), idNominalType);
            Assert.IsInstanceOf <BsonObjectIdGenerator>(idGenerator);
#pragma warning restore
        }