Add comprehensive testing documentation and infrastructure

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This PR adds complete testing documentation and infrastructure for the Simple Task Manager PHP application, following the requested template format.

What's Added

Testing Strategy Documentation (TESTING.md)

• Comprehensive testing plan covering purpose, scope, testing types, and execution procedures
• Detailed documentation of tools and environment setup using PHPUnit 9.5
• Bug and defect management processes with GitHub Issues integration
• Clear instructions for running tests locally and in CI/CD environments

Working Test Infrastructure

• PHPUnit configuration (phpunit.xml) with separate test suites for Unit, Integration, and Functional tests
• Organized directory structure: tests/Unit/, tests/Integration/, tests/Functional/, and tests/fixtures/
• Example unit tests for the Task model demonstrating proper testing patterns
• Enhanced ExampleTest.php with environment verification tests

Developer Resources

• tests/README.md with quick reference for adding new tests
• Test fixtures directory for consistent integration testing
• Updated .gitignore to exclude test artifacts and coverage reports

Testing Coverage Documented

The documentation outlines testing strategy for:

• Task Management: Creation, editing, deletion, status transitions
• Comment System: Adding and retrieving comments with validation
• Tagging System: Tag management and task-tag associations
• Data Storage: JSON file operations with error handling
• Security Features: Input validation, CSRF protection, XSS prevention
• User Interface: Form submissions, filtering, JavaScript interactions

Verification

All tests pass successfully:

$ composer test
PHPUnit 9.6.25 by Sebastian Bergmann and contributors.
....... 7 / 7 (100%)
OK (7 tests, 21 assertions)

The infrastructure is ready for immediate use and provides a solid foundation for maintaining code quality as the application evolves.

Fixes #1.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/sebastianbergmann/exporter/zipball/78c00df8f170e02473b682df15bfcdacc3d32d72
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/zyMJ46 /usr/bin/composer install (http block)
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/global-state/zipball/b6781316bdcd28260904e7cc18ec983d0d2ef4f6
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/zyMJ46 /usr/bin/composer install (http block)
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/object-enumerator/zipball/5c9eeac41b290a3712d88851518825ad78f45c71
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/object-reflector/zipball/b4f479ebdbf63ac605d183ece17d8d7fe49c15c7
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/recursion-context/zipball/539c6691e0623af6dc6f9c20384c120f963465a0
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/zyMJ46 /usr/bin/composer install (http block)
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/resource-operations/zipball/05d5692a7993ecccd56a03e40cd7e5b09b1d404e
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/type/zipball/75e2c2a32f5e0b3aef905b9ed0b179b953b3d7c7
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)
• https://api.github.com/repos/sebastianbergmann/version/zipball/c6c1022351a901512170118436c764e473f6de8c
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/zyMJ46 /usr/bin/composer install (http block)
  • Triggering command: /usr/bin/php8.3 -n -c /tmp/QlSM2G /usr/bin/composer install --no-interaction (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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