How do I get URL from WP_HTTP object?

I’m not sure what you’re after here, but you can try to get the HTTP response object from the WP_HTTP_Requests_Response::get_response_object() method.

Here’s an example to retrieve the url:

if( 
       ! is_wp_error( $test )
    && isset( $test['http_response'] ) 
    && $test['http_response'] instanceof \WP_HTTP_Requests_Response 
    && method_exists( $test['http_response'], 'get_response_object' )
)
    echo $test['http_response']->get_response_object()->url;