public void should_leave_value_alone_when_not_null()
            {
                var converter = new NullSafeValueConverter(typeof(string));
                var result = converter.ToDocument("Sammy");

                Assert.AreEqual("Sammy", result);
            }
            public void should_convert_nulls_into_MongoDBNull()
            {
                var converter = new NullSafeValueConverter(typeof(string));
                var result = converter.ToDocument(null);

                Assert.AreEqual(MongoDBNull.Value, result);
            }