Introduce PHPUnit integration and initial test suite

[dieselxxx]

💢 Feature / Enhancement Pull Request

Related Issue

• Link the issue(s) this PR addresses:
  Closes Introduce PHPUnit testing infrastructure #5

Description

• This PR introduces PHPUnit testing infrastructure into the FireHub Core-Standard repository, along with the initial set of Core validation tests.
• It is needed to establish a formal, automated testing layer for Core contracts and ensure that foundational architectural rules are continuously validated during development and CI execution.
• This improves the FireHub ecosystem by:
  • Introducing a reliable verification layer for Core behavior
  • Enforcing deterministic validation of architectural contracts
  • Reducing regression risk across Core, Runtime Foundation, and downstream packages
  • Establishing testing as a first-class governance mechanism within FireHub
• Context / design notes:
  • PHPUnit is integrated via Composer-based tooling (require-dev)
  • Testing is isolated from the FireHub runtime autoloader (uses Composer autoload instead)
  • Initial tests target Core-level contracts to validate structural integrity and expected behavior
  • This layer is intended to grow into a full ecosystem-wide validation suite across all FireHub editions

Feature Overview

Functional Changes

• Introduced PHPUnit integration into Core-Standard development workflow via firehub/testing dependency
• Added initial testing infrastructure and configuration support (phpunit.xml, bootstrap structure)
• Established foundation for executing unit tests within the Core-Standard repository
• Introduced initial test suite structure for Core domain validation

API / Behavior Changes

• Public API changes:

  • No runtime API changes introduced
  • Testing layer integration via FireHub\Testing\FireHubTestCase

• Internal behavior changes:

  • Core-Standard now depends on firehub/testing for test execution
  • PHPUnit is no longer directly referenced inside Core-Standard
  • Test execution flow is delegated to FireHub Testing layer abstraction

Dependencies

• Added / Updated / Removed:
  • the-firehub-project/testing (dev dependency)
  • phpunit/phpunit (transitive dependency via testing package)
  • PHPUnit integration configuration introduced

Compatibility

• Backward compatible:
  • Yes
  • No (explain below)

Testing

Validation

• Feature implemented according to requirements
• Manual testing completed
• Edge cases verified

Automated Tests

• Unit tests added / updated
• Integration tests added / updated
• Test coverage updated
• All CI checks pass

Documentation

• Changelog updated
• Documentation updated
• Usage examples added / updated
• Migration notes are added (if applicable)

Checklist

• Issue linked
• Feature clearly described
• No unrelated changes are included
• Code self-reviewed
• Follows FireHub coding standards

Risks / Impact

• Risk level:
  • None
  • Low
  • Medium
  • High

Potential Impacts

• Side effects:

  • Introduces testing dependency into development workflow (no runtime impact)

• Affected modules:

  • Core / Runtime / Adapter / Capability (indirect, via shared testing layer)

QA Focus Areas

• Verify PHPUnit executes correctly via vendor/bin/phpunit
• Verify FireHubTestCase inheritance works across Core tests
• Validate autoload-dev and test directory mapping
• Ensure no runtime coupling between Core and PHPUnit

Notes

Technical Notes

• PHPUnit is abstracted behind firehub/testing to avoid direct Core dependency
• Test bootstrap separates runtime configuration from Core logic
• Initial test suite serves as foundation for future Core, Integration, and Architecture test layers

QA / Reviewer Notes

• Focus on correctness of test infrastructure rather than test coverage depth
• Ensure separation between Core runtime code and testing infrastructure is preserved