Add complete database update steps to multinetwork test

Include WordPress downgrade, database version downgrade, site creation, and verification of the actual update-db command execution and success.

Co-authored-by: swissspidy <[email protected]>

Author: Copilot

features/core-update-db.feature

@@ -151,6 +151,8 @@ Feature: Update core's database
       {UPDATE_VERSION}
       """
 
+  # This test downgrades to an older WordPress version, but the SQLite plugin requires 6.0+
+  @require-mysql
   Scenario: Update db respects current network in multinetwork setup
     Given a WP multisite install
     And a disable_sidebar_check.php file:
@@ -161,14 +163,33 @@ Feature: Update core's database
       } );
       """
     And I try `wp theme install twentytwenty --activate`
+    And I run `wp core download --version=5.4 --force`
+    And I run `wp option update db_version 45805 --require=disable_sidebar_check.php`
+    And I run `wp site option update wpmu_upgrade_site 45805`
+    And I run `wp site create --slug=foo`
+    And I run `wp site create --slug=bar`
 
-    # Verify that network ID is determined correctly
     When I run `wp eval "echo defined('SITE_ID_CURRENT_SITE') ? SITE_ID_CURRENT_SITE : 'not defined';"`
     Then STDOUT should contain:
       """
       1
       """
 
+    When I run `wp site option get wpmu_upgrade_site`
+    Then save STDOUT as {UPDATE_VERSION}
+
+    When I run `wp core update-db --network`
+    Then STDOUT should contain:
+      """
+      Success: WordPress database upgraded on 3/3 sites.
+      """
+
+    When I run `wp site option get wpmu_upgrade_site`
+    Then STDOUT should not contain:
+      """
+      {UPDATE_VERSION}
+      """
+
   Scenario: Ensure update-db sets WP_INSTALLING constant
     Given a WP install
     And a before.php file: