Fixes the issue of the Blog menu item and the testimonials archive menu item being 'active' at the same time when using the Testimonials by Woothemes plugin.

testimonials-by-woothemes-menu-fix.php

<?php
/**
 * The plugin bootstrap file
 *
 * This file is read by WordPress to generate the plugin information in the plugin
 * admin area. This file also includes all of the dependencies used by the plugin,
 * registers the activation and deactivation functions, and defines a function
 * that starts the plugin.
 *
 * @link              http://example.com
 * @since             0.0.1
 * @package           Testimonials_By_Woothemes_Menu_Fix
 *
 * @wordpress-plugin
 * Plugin Name:       Testimonials - Menu Fix
 * Plugin URI:        http://chooserethink.com
 * Description:       Fixes the issue of the testimonials archive menu item and the Blog menu item being highlighted at the same time on the testimonials archive page.
 * Version:           1.0.0
 * Author:            Brianna Deleasa @ re:think
 * Author URI:        http://chooserethink.com
 * License:           GPL-2.0+
 * License URI:       http://www.gnu.org/licenses/gpl-2.0.txt
 * Text Domain:       telecom-logos
 * Domain Path:       /languages
 */

// If this file is called directly, abort.
if ( ! defined( 'WPINC' ) ) {
    die;
}

// Define some constants
define( 'TBWMF_POST_TYPE', 'testimonial' );


add_filter( 'nav_menu_css_class', 'tbwmf_nav_menu_css_class', 10, 3 );
/**
 * Fix an issue with both the CPT archive menu item and Blog
 * menu item being highlighted at the same time.  We only want
 * the CPT archive menu item highlighted on the CPT archive page.
 *
 * @param $classes
 * @param $item
 * @param $args
 * @return mixed
 *
 * @since 1.0.0
 */
function tbwmf_nav_menu_css_class( $classes, $item, $args ) {

    if ( is_singular( TBWMF_POST_TYPE ) || is_post_type_archive( TBWMF_POST_TYPE ) ) {
        $blog_page_id = intval( get_option('page_for_posts') );

        if( $blog_page_id !== 0 ) {
            if( $item->object_id == $blog_page_id ) {
                unset( $classes[ array_search( 'current_page_parent', $classes ) ] );
            }
        }
    }

    return $classes;

}