I let the agent write the tests as it built the features. They passed. I ran them, tested by hand, everything green, let it commit. For a while that felt great.
Then I changed a model. A field moved, a type changed, and a pile of tests went red. Not the tests for the thing I changed, tests all over the suite. I fixed them. A week later I changed another model, and it happened again. This kept happening until I stopped and looked at why.
Here's what made it sting. I've been writing tests for a long time, back to my Java days, and the thing I believe about them is simple. A unit test doesn't pay you back the day you write it. It pays you back later, the day you change the code and it catches what you broke. You spend a little now to buy yourself safety in the future. That's the whole deal.
These tests ran that backwards. They cost almost nothing to write and a fortune to keep. Every change broke them, and not because they'd caught a real problem. The one thing tests are supposed to make safe, changing the code, was the exact thing they made painful. That's not a test suite, that's a tax.
What had actually happened
