Tests rendering an external JavaScript file.
function testRenderExternal() {
drupal_add_library('system', 'drupal');
$external = 'http://example.com/example.js';
drupal_add_js($external, 'external');
$javascript = drupal_get_js();
// Local files have a base_path() prefix, external files should not.
$this
->assertTrue(strpos($javascript, 'src="' . $external) > 0, 'Rendering an external JavaScript file.');
}