MDL-80862 testing: Reset task manager between behat tests

lib/behat/classes/util.php

@@ -435,6 +435,9 @@ class behat_util extends testing_util {
         // Inform data generator.
         self::get_data_generator()->reset();
 
+        // Reset the task manager.
+        \core\task\manager::reset_state();
+
         // Initialise $CFG with default values. This is needed for behat cli process, so we don't have modified
         // $CFG values from the old run. @see set_config.
         self::remove_added_config();

lib/classes/task/manager.php

@@ -75,6 +75,15 @@ class manager {
      */
     public static $mode;
 
+    /**
+     * Reset the state of the task manager.
+     */
+    public static function reset_state(): void {
+        self::$miniqueue = null;
+        self::$numtasks = null;
+        self::$mode = null;
+    }
+
     /**
      * Given a component name, will load the list of tasks in the db/tasks.php file for that component.
      *