Tests the actual preview response.
public function testPreviewController() {
$result = $this
->drupalGetAJAX('admin/structure/views/view/test_preview/preview/default');
$result_commands = array();
// Build a list of the result commands keyed by the js command.
foreach ($result as $command) {
$result_commands[$command['command']] = $command;
}
$this
->assertTrue(isset($result_commands['insert']));
}