Should I make a private method public just for testing?

I have a C# service with two methods:

private IEnumerable<RowsBalance> GetUpdatedRowsBalance(IEnumerbale<OrderRows> rows)
{
    //Do something important I want to test
}

public void UpdateBalance(int orderId)
{
    //Gets order rows from database
    var rows = orderRepository.GetRows(orderId);

    //Get updated balance
    var updatedBalanceRows = GetUpdatedRowsBalance(rows);

    //Save updated balance to database
    orderRepository.SaveBalance(updatedBalanceRows);
}

The private method has the logic I need to test, what should I consider in order to make my code testable ?

I'm thinking about:

• Make GetUpdatedRowsBalance public and test that. Is it ok to make something public that will never be called outside of testing ?
• Separate the important business logic I need to test on a different class. Still ok but this is not going to be reused elsewhere.
• Make the public method returns something I can assert like updatedBalanceRows. I don't really like returns something I don't need just for testing.

I'm note sure how to approach this scenario.

You could test it as it is.

Just create your own version of orderRepository.

Here's an example of a very crude API, alter to your preference (or use Moq if you are that way inclined).

// The Test

// Arrange
var orderRepositoryDouble = new OrderRepositoryDouble();
orderRepositoryDouble.Rows = someFakeRows;
var sut = new Whatever(orderRepositoryDouble);

// Act
sut.UpdateBalance();

// Assert
var updatedRows = orderRepositoryDouble.UpdatedRows;

// Whatever.

// The test double
class OrderRepositoryDouble : IRepo
{
    public IEnumerable<OrderRows> Rows { get; set; }
    public GetRows(int orderId) => Rows;

    public IEnumerable<RowsBalance> UpdatedRows { get; set; }

    public void SaveBalance(IEnumerable<RowsBalance> r) =>
        UpdatedRows = r;
}