I found using Test Mode rarely gave a good test of reality. I use Test Mode to ensure my trigger works correctly, not whether it is successful.
It test it's success, I just balance the book.
If I have a Back system I bet the minimum amount [$5], or less it you are only testing for a short period [allowing small bets in setup]. I immediately lodge a counter Lay bet at the bm_backp. I would do this for 1 month or 2 months. Whatever period I needed to determine whether my method was a winner.
I have done the same for Lay bets, backing straight back at the bm_layp.
I rarely missed and in one month I might be -$10. Cheap data analysis I say.
Just my suggestion.