Learning happens when your ideas break, when code fails, unexpected things happen. And in order to have that in a coding agent you need to provide a sensitive skin, which is made of tests, they provide pain feedback to the agent. Inside a good test harness the agent can't break things, it moves in a safe space with greater efficiency than before. So it was the environment providing us with understanding all alone, and we should make an environment where AI can understand what are the effects of its actions.