MDL-79338 core: add support for hook callback redirection in tests

lib/classes/hook/manager.php

@@ -54,6 +54,9 @@ final class manager implements
     /** @var array list of all deprecated lib.php plugin callbacks. */
     private $alldeprecations = [];
 
+    /** @var array list of redirected callbacks in PHPUnit tests */
+    private $redirectedcallbacks = [];
+
     /**
      * Constructor can be used only from factory methods.
      */
@@ -89,6 +92,32 @@ final class manager implements
         return $instance;
     }
 
+    /**
+     * Override hook callbacks for testing purposes.
+     *
+     * @param string $hookname
+     * @param callable $callback
+     * @return void
+     */
+    public function phpunit_redirect_hook(string $hookname, callable $callback): void {
+        if (!PHPUNIT_TEST) {
+            throw new \coding_exception('Invalid call of manager::phpunit_redirect_hook() outside of tests');
+        }
+        $this->redirectedcallbacks[$hookname] = $callback;
+    }
+
+    /**
+     * Cancel all redirections of hook callbacks.
+     *
+     * @return void
+     */
+    public function phpunit_stop_redirections(): void {
+        if (!PHPUNIT_TEST) {
+            throw new \coding_exception('Invalid call of manager::phpunit_stop_redirections() outside of tests');
+        }
+        $this->redirectedcallbacks = [];
+    }
+
     /**
      * Returns list of callbacks for given hook name.
      *
@@ -215,6 +244,14 @@ final class manager implements
             return $event;
         }
 
+        if (PHPUNIT_TEST) {
+            $hookclassname = get_class($event);
+            if (isset($this->redirectedcallbacks[$hookclassname])) {
+                call_user_func($this->redirectedcallbacks[$hookclassname], $event);
+                return $event;
+            }
+        }
+
         $callbacks = $this->getListenersForEvent($event);
 
         if (empty($callbacks)) {