Somebody played my game for one evening with a pen and a piece of paper and found four things that 1115 automated tests had not.
It was Samanta, my partner. She was not reviewing it. She just played, and took notes.
The one that stung
A whole paragraph I wrote was never in the game. A letter asking the player where they got stuck. Two different texts were sitting under one key, and in C# that is an assignment rather than a duplicate, so the second silently wins and the first stops existing.
No error. Tests green. A paragraph that only lives in a file.
The best one was the music
She wrote three loops for the game. I listened, told her they were clicking at the seam, and suggested a second of fade at the end.
So I measured it. There is no click. What there is, is a step in density: the arrangement thins out at the end and comes back full, and you hear it every twenty four seconds.
Her diagnosis was right. Her cause was wrong. My proposed fix would have made it measurably worse.
I did the opposite, and my first attempt produced a real click, eighty three times a normal step. It was caught by a test she had designed and could not run, because she does not have the engine on her machine and would not hand me a test she had never executed.
She heard it. I measured it. Her test caught my mistake in the fix to her problem.
What has somebody outside your project found that you had been looking straight at?