Update the README's test suites section

Signed-off-by: Matthew Setter <matthew@matthewsetter.com>

This change replaces the Test suites section copied over from phpdb's
README in the previous commit with one that is applicable to this
project, specifically.

Author: settermjd

README.md

@@ -28,22 +28,21 @@ This section outlines specifics for php-db.
 
 ### Test suites
 
-The `phpunit.xml.dist` file defines two test suites, "unit test" and "integration test".
-You can run one or the other using the `--testsuite` option to `phpunit`:
+To run the project's test suite, run the command below:
 
 ```bash
-./vendor/bin/phpunit --testsuite "unit test" # unit tests only
-./vendor/bin/phpunit --testsuite "integration test" # integration tests only
+composer check
 ```
 
-Unit tests do not require additional functionality beyond having the appropriate database extensions present and loaded in your PHP binary.
+This [Composer script][composer-scripts] runs both the unit and integration tests, as well as code style and static analysis.
 
 ---
 
 - File issues at <https://github.com/php-db/phpdb-sqlite/issues>
 - Documentation is at <https://docs.php-db.dev>
 
 [composer]: https://getcomposer.org
+[composer-scripts]: https://getcomposer.org/doc/articles/scripts.md
 [laminas-db]: https://docs.laminas.dev/laminas-db/
 [php-db]: https://github.com/php-db/phpdb
 [php-pdo-extension]: https://www.php.net/manual/en/pdo.installation.php