Testing isn't a linear thing where you start on one end and know 100 meters down the line where you are done and every step is the same. Discovering and fixing bugs is like solving a random puzzle. You have to take each step as a new challenge, sometimes its a breeze and just works, sometimes you discover some big or small things on the way, sometimes the fix itself might cause other problems. You can't search for how to solve your specific problem many times because you have a unique situation and a unique implementation, and who's to say that the "solution" out there is actually a good one. All you can do is understand your own project 100% how every component works, and how it should work, and go through every step on the way to verify that you get your expected result.
Keep in mind that compared to most other visual novels that are all about adding more content, we also focus on making the game client better, up-to-date, fast, fun, bring in unique features etc every single release. That's why it takes more testing. The development itself like adding content doesn't suffer because the responsibilities are separated in the team.
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Kidding aside Motkeyz and his team is by far the best devs there is..
