Claude Code Practical Guide: Debugging, Test Automation, and CUDA Environment Setup with Opus 4.6

Introduction Claude Code is a CLI (Command Line Interface) tool provided by Anthropic that allows you to directly invoke Claude Opus 4.6 from your terminal to perform coding, debugging, and environment setup. Its distinct feature is that it is editor-independent and can be directly integrated into your existing workflows. In this article, we explain the following practical use cases using Claude Code: Project control via CLAUDE.md for cost and quality management A debugging case study of a Flask app Automatic generation of pytest test code Assistance in setting up an RTX 5090 + CUDA 13.1 environment CI/CD automation with GitHub Actions Chapter 1: Project Control with CLAUDE.md Claude Code automatically reads CLAUDE.md in the project root to control the AI's behavior. This eliminates the need to provide instructions in every prompt, allowing you to obtain consistent outputs across the entire team. Example of CLAUDE.md: # CLAUDE.md - Reply in Japanese - Always include Python type hints i