Blog
Releasing testcase.ac as open source
TL;DR: Both the data and the web service code of testcase.ac are going open source. The code is at testcase-ac/testcase-ac, and you can preview the new service at next.testcase.ac. Introduction Hello, I’m the developer of testcase.ac. On April 15, the shutdown of Baekjoon Online Judge (hereafter BOJ1) was announced. BOJ has been the most familiar service for almost anyone in Korea who has ever tried solving algorithm problems. I myself once spent my days finding joy in solving problems on BOJ, so this announcement was, just like it was for many others, a very sad and disappointing piece of news to me.
April 25, 2026
A Look Back at the First Year of testcase.ac
(This is automatically translated via Codex from Korean version) Hello, I am Jaechan Lee, the developer of testcase.ac. On Baekjoon, I use the handle dlwocks31. I started developing testcase.ac in August 2024, and the service properly launched together with the Baekjoon board post Introducing testcase.ac, a project that finds counterexamples for my code! on October 5, 2024. It now gets around 500 visitors per day on average, with about 2,000 submissions every day. That is a meaningful amount of usage.
September 26, 2025