compareMongoObjectIds(expected, result) {
    var expectedString = expected.toString();
    var resultString = result.toString();

    if (result instanceof mongodb.ObjectId !== true) return false;
    if (expectedString !== resultString) return false;
    return true;
  }
Tests that the resulting objectId is an instance of mongodb.ObjectId
and tests that it matches the toString value of the expected ObjectId
@param  {ObjectId} expected The ObjectId that's expected
@param  {ObjectId} result   The ObjectId that's returned
@return {[type]}          [description]