Add PHPUnit tests for wp_widgets_add_menu function

tests/phpunit/tests/functions/wpWidgetsAddMenu.php

@@ -0,0 +1,68 @@
+<?php
+
+/**
+ * Tests for the wp_widgets_add_menu function.
+ *
+ * @group functions
+ *
+ * @covers ::wp_widgets_add_menu
+ */
+class Tests_Functions_wpWidgetsAddMenu extends WP_UnitTestCase {
+
+	public $submenu;
+
+	public function set_up() {
+		global $submenu;
+		$this->submenu = $submenu;
+		$submenu       = null;
+	}
+
+	public function tear_down() {
+		global $submenu;
+		$submenu = $this->submenu;
+	}
+
+	/**
+	 * @ticket 60179
+	 */
+	public function test_wp_widgets_add_menu() {
+		global $submenu;
+		wp_widgets_add_menu();
+
+		$expected['themes.php'][7] = array( __( 'Widgets' ), 'edit_theme_options', 'widgets.php' );
+		$this->assertEqualSets( $expected, $submenu );
+	}
+
+	/**
+	 * @ticket 60179
+	 */
+	public function test_wp_widgets_add_menu_no_widget_support() {
+		global $submenu;
+
+		add_filter( 'current_theme_supports-widgets', '__return_false' );
+
+		wp_widgets_add_menu();
+
+		remove_filter( 'current_theme_supports-widgets', '__return_false' );
+
+		$this->assertNull( $submenu );
+	}
+
+	/**
+	 * @ticket 60179
+	 */
+	public function test_wp_widgets_add_menu_block_template_parts_supported() {
+		global $submenu, $_wp_theme_features;
+
+		$_wp_theme_features['block-template-parts'] = true;
+		add_filter( 'current_theme_supports-block-template-parts', '__return_true' );
+
+		wp_widgets_add_menu();
+
+		unset( $_wp_theme_features['block-template-parts'] );
+		remove_filter( 'current_theme_supports-block-template-parts', '__return_true' );
+
+		$expected['themes.php'][] = array( __( 'Widgets' ), 'edit_theme_options', 'widgets.php' );
+		$this->assertEqualSets( $expected, $submenu );
+	}
+}