If this is only for mocking purposes you should consider making this ctor protected and add doc comment. In EF we used the following generic message for this: 
```
        /// <summary>
        ///     This constructor is intended only for use when creating test doubles that will override members
        ///     with mocked or faked behavior. Use of this constructor for other purposes may result in unexpected
        ///     behavior including but not limited to throwing <see cref="NullReferenceException" />.
        /// </summary>
```