Ignore phpunit.cache and vendor folder

[chrisdicarlo]

This pull request introduces a comprehensive automated testing workflow to the project, including new PHPUnit configuration files, test fixtures, and integration tests. It adds a GitHub Actions workflow for continuous integration, sets up Composer for test dependencies, and documents the testing process. The changes ensure that tests are run across multiple PHP versions, provide a robust suite of example tests and fixtures, and verify end-to-end behavior of the phpunit-failed-runner script.

Continuous Integration and Composer Setup

• Added a GitHub Actions workflow (.github/workflows/tests.yml) to automatically run tests on pushes and pull requests for multiple PHP versions.
• Updated composer.json to include PHPUnit as a development dependency, configured PSR-4 autoloading for tests, and added a Composer test script for easy execution.

Testing Infrastructure

• Added PHPUnit configuration files (phpunit.xml and phpunit-integration-fixtures.xml) to define test suites, source directories, and integration test setups. [1] [2]
• Created test fixtures and corresponding test cases in the tests/Fixtures and tests directories, demonstrating both passing and failing behaviors for incremental test fixing. [1] [2] [3] [4] [5] [6]

Integration and Script Testing

• Added a comprehensive integration test (tests/Integration/ScriptBehaviorTest.php) that verifies the end-to-end behavior of the bin/phpunit-failed-runner script, including its handling of failing tests, logfiles, XML transformations, and output messages.

Documentation

• Updated README.md with instructions for running the test suite.