Add comprehensive unit tests for Security, UserModel, and Validation utilities

- Implemented SecurityTest to validate token generation, CSRF protection, input sanitization, and rate limiting.
- Created UserModelTest to ensure correct database operations for user management, including creation, updating, banning, and fetching active users.
- Developed ValidationTest to verify input validation and sanitization for user IDs, nicknames, messages, and API requests.
- Introduced Security and Validation utility classes with methods for secure token generation, input sanitization, and comprehensive validation rules.

tests/bootstrap.php

@@ -0,0 +1,138 @@
+<?php
+/**
+ * PHPUnit Test Bootstrap
+ * Sets up test environment and dependencies
+ */
+
+// Define test environment
+define('TESTING', true);
+define('APP_ENV', 'testing');
+
+// Include autoloader if it exists, otherwise manually load classes
+if (file_exists(__DIR__ . '/../includes/autoloader.php')) {
+    require_once __DIR__ . '/../includes/autoloader.php';
+}
+
+// Initialize error handling for tests
+if (class_exists('ErrorHandler')) {
+    ErrorHandler::initialize();
+}
+
+// Set up test database configuration
+$_ENV['APP_ENV'] = 'testing';
+$_ENV['DB_DATABASE'] = ':memory:'; // Use in-memory SQLite for tests
+$_ENV['DB_DRIVER'] = 'sqlite';
+
+// Mock session for testing
+if (!isset($_SESSION)) {
+    $_SESSION = [];
+}
+
+// Mock POST/GET data if needed
+if (!isset($_POST)) {
+    $_POST = [];
+}
+if (!isset($_GET)) {
+    $_GET = [];
+}
+if (!isset($_SERVER)) {
+    $_SERVER = [
+        'REQUEST_METHOD' => 'GET',
+        'HTTP_HOST' => 'localhost',
+        'SERVER_NAME' => 'localhost',
+        'SERVER_PORT' => '80',
+        'REQUEST_URI' => '/',
+        'SCRIPT_NAME' => '/index.php',
+        'PHP_SELF' => '/index.php',
+        'REMOTE_ADDR' => '127.0.0.1',
+        'HTTP_USER_AGENT' => 'PHPUnit/Test'
+    ];
+}
+
+// Initialize PDO for in-memory SQLite testing
+class TestDatabaseHelper
+{
+    private static $pdo = null;
+
+    public static function getTestPdo()
+    {
+        if (self::$pdo === null) {
+            self::$pdo = new PDO('sqlite::memory:');
+            self::$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
+            self::$pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
+
+            // Enable WAL mode for better testing performance
+            self::$pdo->exec('PRAGMA journal_mode=WAL');
+            self::$pdo->exec('PRAGMA synchronous=NORMAL');
+        }
+
+        return self::$pdo;
+    }
+
+    public static function setupTestSchema()
+    {
+        $pdo = self::getTestPdo();
+
+        // Create tables for testing
+        $sql = file_get_contents(__DIR__ . '/../migrations/001_create_tables.sql');
+        $pdo->exec($sql);
+
+        // Insert test data if needed
+        self::insertTestData($pdo);
+    }
+
+    private static function insertTestData($pdo)
+    {
+        // Insert some test users
+        $pdo->exec("INSERT INTO users (user_id, nickname, ip_address, session_id, last_seen)
+                   VALUES ('test_user_1', 'TestUser1', '192.168.1.100', 'session_123', datetime('now'))");
+
+        $pdo->exec("INSERT INTO users (user_id, nickname, ip_address, session_id, last_seen)
+                   VALUES ('test_user_2', 'TestUser2', '192.168.1.101', 'session_456', datetime('now'))");
+
+        // Insert test messages
+        $pdo->exec("INSERT INTO chat_messages (user_id, nickname, message, is_admin, ip_address, time_formatted)
+                   VALUES ('test_user_1', 'TestUser1', 'Hello from test user 1', 0, '192.168.1.100', '12:00')");
+
+        $pdo->exec("INSERT INTO chat_messages (user_id, nickname, message, is_admin, ip_address, time_formatted)
+                   VALUES ('test_user_2', 'TestUser2', 'Hello from test user 2', 0, '192.168.1.101', '12:01')");
+
+        // Insert test active viewers
+        $pdo->exec("INSERT INTO active_viewers (user_id, nickname, ip_address, session_id, is_admin, last_seen)
+                   VALUES ('test_user_1', 'TestUser1', '192.168.1.100', 'session_123', 0, datetime('now'))");
+    }
+
+    public static function teardown()
+    {
+        self::$pdo = null;
+    }
+}
+
+// Clean up any existing test artifacts
+function cleanupTestEnvironment()
+{
+    // Clear test session data
+    $_SESSION = [];
+
+    // Remove any test files
+    $testFiles = [
+        __DIR__ . '/../logs/app.log',
+        __DIR__ . '/../active_viewers.json.backup',
+        __DIR__ . '/../chat_messages.json.backup'
+    ];
+
+    foreach ($testFiles as $file) {
+        if (file_exists($file)) {
+            @unlink($file);
+        }
+    }
+}
+
+// Set up test environment
+cleanupTestEnvironment();
+
+// Register shutdown function to clean up
+register_shutdown_function(function() {
+    TestDatabaseHelper::teardown();
+    cleanupTestEnvironment();
+});