The page silently bounced you back

Today's fix is small, but I had not noticed it for a long time. When signing in to the learning platform, if the password was wrong the page bounced back to the login screen without showing any message. From the outside the page just flickers once and nothing changes. Why it happened is clear enough. The code had a rule that sent the user to the login page whenever sign-in failed. And it did not distinguish between kinds of failure: wrong password, expired session, or server not responding — all ended the same way. I had not noticed because I know my own password and always type it correctly. Someone else reported it — they had mistyped the password twice and assumed the app was broken. The fix: the behaviour now depends on the reason. Wrong password — a clear message appears and the user stays on the page. Expired session — a different message. Server not responding — a third one. This case reminded me of something: the developer is the worst tester of their own work, because they know how to do everything correctly. Bugs are usually found by someone else.