30 years coding and this is the first time I pay to verify some code I wrote.
I wrote a Klondike solver and I couldn't find a better way to test it than reproduce two solutions with a physical deck, so I had to buy one.
Theoretically, about 80% of starting positions are solvable. My solver only does about 50%, but I can only to 14%, so I guess I'm happy.
Fun how I wrote a Sokoban solver that beat me easily on a set of mazes. (Another popular set of mazes is better for humans- I won there.)