How to Write Manual Test Cases — Structure, Template and Four Rules from a Project with a Coding Agent

In mid-September 2026 the catalog of manual test cases in the DI² project had 32 active entries. 27 of them existed only because something had been broken before. For just two test cases, what has to be visible on screen was settled before the code existed. A catalog that came almost entirely from bugs secures … Read more

The First Run Tests the Test Case — What a Test Case Is Worth When Nobody Has Ever Executed It

A manual test case in the DI² project had everything the convention asks for: a header with goal and precondition, a step table with step and expectation, an entry in the catalog overview, references to the files it covers. The catalog’s automatic structural check had accepted it. On the first execution it turned out that … Read more

The Green Test That Proves Nothing — Why a Passing Test Suite Confirmed the Bug It Was Supposed to Catch

A bug on the DI² project’s website counted as fixed for four weeks. When the reader switches the language, the page is supposed to stay at the spot where the reader was. Three fix commits had promised that one after another, each with its own diagnosis, and after each one the automated test suite was … Read more

The Control Loop — How I Get AI-Generated Code Checked That I Can’t Read Myself

Reading code in order to control it takes two things: the language and the time. In the DI² project, both are missing. The maintainer comes from database development and knows neither TypeScript nor the web development the application is built in. And even someone who knows the language no longer reads through the amount of … Read more

The Agent Measures Where I Click — Debugging Postgres, Docker and a Swapping Server with a Coding Agent

A bug gets reported the way it feels: the message does not appear, the page barely responds, a tab no longer loads after a restart. A user can only describe what the interface shows, and the interface is the end of a long chain. A coding agent with access to the database, the container runtime … Read more

One VPS, Four Environments, No Cookie Banner — How I Host a Next.js App with Self-Hosted Keycloak

For most web applications, the cookie banner question comes up too late. The application is built, an analytics script is in, the login page comes from a cloud service, and suddenly the very first page view needs a consent dialog that nobody planned for. The DI² project turned the question around. GDPR without a cookie banner was … Read more

Two Agents, One Working Tree — What Broke When I Ran Parallel Claude Code Sessions in One Git Repository

A Claude Code session opens a Git repository with no pending changes, works for half an hour and commits whatever has changed at the end. Run alone, that is correct. As soon as a second session or a human works in the same repository, the very same routine can pull someone else’s work into the … Read more

Agentic Coding from a User’s Perspective — Experience: The Work Doesn’t Disappear, It Shifts

Since spring 2026, two projects have been taking shape with the same coding agent: an ETL generator on Next.js and PostgreSQL, and this blog. The agent does not complete lines, it works through assignments in the repository. This article collects my agentic coding experience from a user’s perspective. I build databases, ETL processes and the … Read more