D7: theme template in module

theme.php

<?php
# ------------------------------------------------------------------------------
# test.module
# ------------------------------------------------------------------------------
/**
 * Implements hook_theme().
 */
function test_theme() {
  return array(
    'test_panel' => array(
      'variables' => array(),
      'template' => 'test-panel',
      'path' => drupal_get_path('module', 'test') . '/templates'
    ),
  );
}

// Some callback function..
function test_page() {
  $template = theme('test_panel', array(
    'data' => array(
      'test' => 'data'
    )
  );
  return $template;
}

# ------------------------------------------------------------------------------
# templates/test-panel.tpl.php
# ------------------------------------------------------------------------------
<code><?php print_r($data); ?></code>