Introduce PHPUnit testing infrastructure

[dieselxxx]

Affected Version

v0.0.0

Testing Type

Test Automation

Pre-check

• I have checked existing tests and testing tasks

Scope

Core Standard testing infrastructure including:

• ValueObject base abstraction
• Entity and AggregateRoot contracts (if applicable)
• Core architectural boundaries
• PHPUnit CI pipeline integration

Testing Objective

Validate that Core Standard components behave correctly under PHPUnit execution,
and ensure that all architectural contracts and abstractions can be safely tested.

Ensure CI pipeline executes tests consistently on every pull request.

Test Cases

• ValueObject equality comparison tests
• ValueObject immutability validation
• Entity identity consistency checks
• AggregateRoot structural integrity tests (if applicable)
• Core contract implementation validation
• PHPUnit bootstrap and CI execution validation

Test Setup

• PHPUnit installed via composer require-dev
• phpunit.xml configuration file
• CI pipeline integration via GitHub Actions
• Core autoloading via Composer

Expected / Actual Results

Expected:

• All Core contracts pass PHPUnit tests
• CI pipeline executes successfully on pull request

Actual:

• Initial setup validation pending execution

Automation (if applicable)

PHPUnit runs automatically on every pull_request via GitHub Actions workflow.
This ensures all Core changes are validated before merge into develop or release branches.

Additional Context

This testing layer is part of FireHub's development-time validation system
and complements PHPStan static analysis infrastructure.