MadLab Tesuji Solver is a program for solving open-space capture problems. Written in Java, MadLab runs on all major platforms and is available at https://t-t.dk/madlab. MadLab was commercial but is now free of charge in its full version.
The program guarantees 100% correctness of its solutions, and it can also analyze whole games, scanning them for tesuji.
MadLab comes with 997 capture problems extracted from real high-level games. The 997 capture problems can also be freely downloaded as SGF files here: https://t-t.dk/madlab/problems.
Example of an open-space capture problem (Lucky's Problem):