Count author posts in certain category

I am using this code to only get authors who have posted in the 'Travel' category but the part 'category_name' = 'travel' doesn't seem to work. The code currently gets all posts in all categories.

?php
$args = array(
    'exclude' = array( 10, 18 ),
    'role' = 'contributor',
    'category_name' = 'travel',
);

$wp_user_query = new WP_User_Query($args);
$authors = $wp_user_query-get_results();

if (!empty($authors)) {
    foreach ($authors as $author) {
        if ( count_user_posts($author-ID) = 1 ) {
            
        }
    }
}