Updated readme

Author: korridor

readme.md

@@ -99,19 +99,24 @@ public function rules()
 
 I am open for suggestions and contributions. Just create an issue or a pull request.
 
-### Testing
+### Local docker environment
+
+The `docker` folder contains a local docker enironment for development.
+The docker workspace has composer and xdebug installed.
 
 ```bash
-composer test
-composer test-coverage
+docker-compose run workspace bash
 ```
 
+### Testing
+
+The `composer test` command runs all tests with [phpunit](https://phpunit.de/).
+The `composer test-coverage` command runs all tests with phpunit and creates a coverage report into the `coverage` folder.
+
 ### Codeformatting/Linting
 
-```bash
-composer fix
-composer lint
-```
+The `composer fix` command formats the code with [php-cs-fixer](https://github.com/FriendsOfPHP/PHP-CS-Fixer).
+The `composer lint` command checks the code with [phpcs](https://github.com/squizlabs/PHP_CodeSniffer).
 
 ## Credits