As often the case, asking the question reveals the answer:
Use global $authordata;. Fix php errors: == operator. Fix $rid=’445′, not $rid=445.
Here’s the working code:
add_action ('genesis_before_sidebar_widget_area','user_testimonials',10);
function user_testimonials(){
if (is_author() || is_singular('post')){
global $authordata; //using global $authordata is more direct
$authorlogin = $authordata->user_login;
//print_r( $authordata ); //to see everything
if (is_author('author-1') || ($authorlogin=="author-1") ) //Fix the == operators
{
$rid='445';
}
elseif (is_author('author-2') || ($authorlogin=='author-2') )
{
$rid='451';
}
echo "<section class="widget"><h3 class="widget-title"> Testimonials </h3>";
echo do_shortcode('
[testimonial_rotator id='. $rid .' hide_title="true" format="list"]')
. '</section>';
}
}