Tests behavior of ajax_render_error().
function testAJAXRenderError() {
// Verify custom error message.
$edit = array(
'message' => 'Custom error message.',
);
$commands = $this
->drupalGetAJAX('ajax-test/render-error', array(
'query' => $edit,
));
$expected = new AlertCommand($edit['message']);
$this
->assertCommand($commands, $expected
->render(), 'Custom error message is output.');
}