Writing a unit test for add_menu_page

I am writing a few unit tests for a plugin that I have developed. However I seem to be hung up on testing one (seemingly) simple piece of code.

In the plugin I’ve written I have registered an admin menu page:

add_menu_page(
    esc_html__( 'Places', 'wp-places' ),
    esc_html__( 'Places', 'wp-places' ),
    'manage_options',
    'wp-places',
    [ $this, 'places_page' ],
);

But I can’t seem to come up with a unit test to ensure this menu item exists. I’ve seen a few uses of global $menu, but when I check the global it isn’t yet set.

Here is the very basics of what I have.

<?php

class AdminTests extends WP_UnitTestCase {

    public function setUp() {

        parent::setUp();

        wp_set_current_user( self::factory()->user->create( [
            'role' => 'administrator',
        ] ) );

        $this->go_to( admin_url() );

    }

    public function test_admin_menu() {

        global $menu;

        print_r( $menu ); // not set

    }

}

Rather than worrying about the internal implementation of the menu code and the globals that it uses (there are several beside $menu), I’d use a function like menu_page_url() to check if the page exists. That function will return the URL if the menu is registered, or an empty string if it is not. So you could do:

$this->assertNotEmpty( menu_page_url( 'my_menu_slug' ) );

Additionally, you are not setting up the test correctly. The go_to() method only sets up the main WP_Query object, it doesn’t work for admin URLs. You need to instead call your function that registers the admin menu. So your test would look something more like this:

class AdminTests extends WP_UnitTestCase {

    public function setUp() {

        parent::setUp();

        wp_set_current_user( self::factory()->user->create( [
            'role' => 'administrator',
        ] ) );
    }

    public function test_admin_menu() {

        my_admin_menu_registration_func();

        $this->assertNotEmpty( menu_page_url( 'my_menu_slug' ) );
    }

}