ParentFixture.php

<?php

class ParentFixture extends CakeTestFixture {
	public $import = array();
	protected $hasData = false;
	protected static $truncating = false;
	protected static $log = array();

	public function insert($db) {
		self::$truncating = false;
		if ($this->hasData) {
			return;
		}

		parent::insert($db);
		$this->hasData = true;
	}

	public function truncate($db) {
		if (!self::$truncating) {
			self::$log = $db->getLog(false, true);
			self::$truncating = true;
		}

		foreach (self::$log['log'] as $i => $q) {
			if (preg_match('/^UPDATE|^INSERT/i', $q['query'])) {
				if (strpos($q['query'], $db->fullTableName($this->table, false, false)) !== false) {
					parent::truncate($db);
					$this->hasData = false;
					return;
				}
			} else {
				unset(self::$log['log'][$i]);
			}
		}
	}

}