use get_template_part() in a shortcode without outputting the html arbitrarily due to the behind the scenes 'require.'

Shortcodes with get_template_part()

add_shortcode('donation-posts', 'fnDonatePosts');   
function fnDonatePosts($attr, $content)
{        
    ob_start();  
    get_template_part('donation', 'posts');  
    $ret = ob_get_contents();  
    ob_end_clean();  
    return $ret;    
}