How to Use Claude Code

Opening excerpt

The change that was not ready

At 4:42 on a wet Thursday, Mara had a green test result and a reason to distrust it.

The community workshop's booking page had accepted two reservations for the same lathe. One member had taken an afternoon off work. Another had borrowed a van. Both arrived carrying timber. The caretaker opened the calendar, saw two names in the same square, and called the developer who had offered to maintain the site.

Mara asked an assistant to fix the booking conflict. A few minutes later, a new check appeared in the application. The assistant reported success. The booking form refused the duplicate example Mara had shown it. She could have sent a reassuring message and gone home.

Instead, she opened the test.

It checked whether a helper returned false when given a list containing a matching reservation. It did not start two requests. It did not ask the database to reject a collision. It did not show what would happen if another person booked between the first request's check and its save.

The test was green because the test's question was small. The workshop's problem was larger.

Mara, the caretaker, and the workshop are fictional. Their predicament is a teaching construction, not a customer story or a report of a Claude Code test. We will return to it because it exposes a useful distinction: producing a change and establishing that the change solves the problem are different jobs.