WordPress theme setup

Core.php

<?php

namespace Bahama;

class Core {
    public function setup() {
        add_action('after_setup_theme', [$this, 'i18n']);
        add_action('after_setup_theme', [$this, 'theme_setup']);
        add_action('wp_enqueue_scripts', [$this, 'scripts']);
        add_action('wp_enqueue_scripts', [$this, 'styles']);
    }

    public function i18n() {
        load_theme_textdomain('bahama', BAHAMA_PATH . '/languages');
    }

    public function theme_setup() {
        add_theme_support('automatic-feed-links');
        add_theme_support('title-tag');
        add_theme_support('post-thumbnails');
        add_theme_support('html5', ['search-form', 'gallery']);

        register_nav_menus(
            [
                'primary' => esc_html__('Primary Menu', 'bahama'),
            ]
        );
    }

    public function scripts() {
        wp_enqueue_script(
            'bahama-app',
            BAHAMA_TEMPLATE_URL . 'assets/js/app.js',
            [],
            BAHAMA_VERSION,
            true
        );
    }

    public function styles() {
        wp_enqueue_style(
            'bahama-stylesheet',
            get_stylesheet_uri(),
            [],
            BAHAMA_VERSION
        );
    }
}

functions.php

<?php

define('BAHAMA_VERSION', '0.1.0');
define('BAHAMA_TEMPLATE_URL', get_template_directory_uri());
define('BAHAMA_PATH', get_template_directory() . '/');
define('BAHAMA_INC', BAHAMA_PATH . 'includes/');

if (file_exists(__DIR__ . '/vendor/autoload.php')) {
    require_once 'vendor/autoload.php';

    $core = new Bahama\Core;
    $core->setup();
}

Helpers.php

<?php

namespace Bahama;

class Helpers
{
    public function get_body_class() {
        echo 'test';
    }
}

index.php

<?php

get_header(); ?>

<?php if (have_posts()) : ?>
    <?php while (have_posts()) : the_post(); ?>
        <h2><?php the_title(); ?></h2>
        <?php the_content(); ?>
        <?php Bahama\Helpers::get_body_class(); ?>
    <?php endwhile; ?>
<?php endif; ?>

<?php
get_footer();