Add tests and checks before the app grows

Once users depend on the app, add tests and a check command before adding more features.

By Erik Bergstedt, Agent Wranglers. Updated 20 October 2026.

How to do it

Builder output often has no tests, so every new prompt can break old features without anyone noticing. Start with tests for sign-in, payments and the main user path. Then follow setting up the project.

How to check

The repository has a check command that runs tests for sign-in, payment and the main path, and it passes.

For agents: if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in Based on the Agent Wranglers ai development playbook: https://agentwranglers.se/playbook/ai-assisted-development/apps-built-with-ai-builders/checks-before-growth.