MDL-70763 gradereport_grader: export preferences for correct user.

grade/report/grader/classes/privacy/provider.php

@@ -87,7 +87,7 @@ class provider implements
      * @param   int         $userid The userid of the user whose data is to be exported.
      */
     public static function export_user_preferences(int $userid) {
-        $preferences = get_user_preferences();
+        $preferences = get_user_preferences(null, null, $userid);
         foreach ($preferences as $name => $value) {
             $prefname = null;
             $prefdescription = null;

grade/report/grader/tests/privacy_test.php

@@ -63,14 +63,18 @@ class gradereport_grader_privacy_testcase extends \core_privacy\tests\provider_t
      * These preferences can be set on each course, but the value is shared in the whole site.
      */
     public function test_export_user_preferences_single() {
-        // Add some user preferences.
+        // Create test user, add some preferences.
         $user = $this->getDataGenerator()->create_user();
         $this->setUser($user);
+
         set_user_preference('grade_report_showcalculations', 1, $user);
         set_user_preference('grade_report_meanselection', GRADE_REPORT_MEAN_GRADED, $user);
         set_user_preference('grade_report_studentsperpage', 50, $user);
 
-        // Validate exported data.
+        // Switch to admin user (so we can validate preferences of our test user are still exported).
+        $this->setAdminUser();
+
+        // Validate exported data for our test user.
         provider::export_user_preferences($user->id);
         $context = context_user::instance($user->id);
         $writer = writer::with_context($context);