Example of WP unit tests with Pest. Doesn't include the entire setup, for that you can check https://github.com/dingo-d/wp-pest-integration-test-setup

BookCptOOPTest.php

<?php

use TestPlugin\Cpt;

// Unit test with OOP code.

it('checks that the hook is registered for custom post type registration', function() {
  $this->stubTranslationFunctions();
  
  (new RegisterBookCpt())->register();
  
  // We use Brain Monkey lib:
  // https://giuseppe-mazzapica.gitbook.io/brain-monkey/wordpress-specific-tools/wordpress-hooks-added
  $this->assertNotFalse(has_action('init', [RegisterBookCpt::class, 'test_plugin_register_books_cpt']));
});

BookCptProceduralTest.php

<?php

// Unit test with procedural code.

it('checks that the hook is registered for custom post type registration', function() {
  $this->stubTranslationFunctions();
  
  // Assume that our tests are in a 'tests' directory in the root of the plugin
  // And inside a 'Unit' folder. We need to manually include our code if we don't use autoloader.
  
  require dirname(__DIR__, 2) . '/test-plugin-procedural.php';
  
  // We use Brain Monkey lib:
  // https://giuseppe-mazzapica.gitbook.io/brain-monkey/wordpress-specific-tools/wordpress-hooks-added
  $this->assertNotFalse(has_action('init', 'test_plugin_register_books_cpt'));
});

Pest.php

<?php

use Yoast\WPTestUtils\BrainMonkey\TestCase;

uses()->group('integration')->in('Integration');
uses()->group('unit')->in('Unit');

uses(TestCase::class)->in('Unit', 'Integration');

RegisterBookCpt.php

<?php

namespace TestPlugin\Cpt;

class RegisterBookCpt {
  public function register() {
    \add_action( 'init', [$this, 'registerBooksCpt'] );
  }
  
  public function registerBooksCpt() {
    $args = array(
        'label'              => esc_html__( 'Books', 'test-plugin' ),
        'public'             => true,
        'publicly_queryable' => true,
        'show_ui'            => true,
        'show_in_menu'       => true,
        'query_var'          => true,
        'rewrite'            => array( 'slug' => 'book' ),
        'capability_type'    => 'post',
        'has_archive'        => true,
        'hierarchical'       => false,
        'menu_position'      => null,
        'supports'           => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' ),
    );
 
    register_post_type( 'book', $args );
  }
}

test-plugin-procedural.php

<?php

/**
 * Plugin Name: Test plugin
 * Desctiption: Test plugin
 * Version: 1.0.0
 * License: MIT
 */

function test_plugin_register_books_cpt() {
    $args = array(
        'label'              => esc_html__( 'Books', 'test-plugin' ),
        'public'             => true,
        'publicly_queryable' => true,
        'show_ui'            => true,
        'show_in_menu'       => true,
        'query_var'          => true,
        'rewrite'            => array( 'slug' => 'book' ),
        'capability_type'    => 'post',
        'has_archive'        => true,
        'hierarchical'       => false,
        'menu_position'      => null,
        'supports'           => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' ),
    );
 
    register_post_type( 'book', $args );
}
 
add_action( 'init', 'test_plugin_register_books_cpt' );

test-plugin.php

<?php

namespace TestPlugin;

use TestPlugin\Cpt;

/**
 * Plugin Name: Test plugin class
 * Desctiption: Test plugin but with class instead of procedural code
 * Version: 1.0.0
 * License: MIT
 */

require_once dirname(__FILE__) . '/vendor/autoload.php';
 
// Same as previous example but in class context. We are using PSR-4 autoloading.
(new RegisterBookCpt())->register();