Add more instructions to CLAUDE.md file

Author: OskarStark

CLAUDE.md

@@ -108,4 +108,7 @@ Each component uses:
 - Each component in `src/` is a separate Composer package with its own dependencies
 - Use `@dev` versions for internal component dependencies during development
 - Components follow Symfony coding standards and use `@Symfony` PHP CS Fixer rules
-- The monorepo structure allows independent versioning while maintaining shared development workflow
+- The monorepo structure allows independent versioning while maintaining shared development workflow
+- Do not use void return type for testcase methods
+- Always run PHP-CS-Fixer to ensure proper code style
+- Always add a newline at the end of the file