MDL-69507 duration form field: should return an int number of seconds

lib/form/duration.php

@@ -34,7 +34,7 @@ require_once($CFG->libdir . '/form/text.php');
  * Duration element
  *
  * HTML class for a length of time. For example, 30 minutes of 4 days. The
- * values returned to PHP is the duration in seconds.
+ * values returned to PHP is the duration in seconds (an int rounded to the nearest second).
  *
  * @package   core_form
  * @category  form
@@ -301,6 +301,7 @@ class MoodleQuickForm_duration extends MoodleQuickForm_group {
         if ($this->_options['optional'] && empty($valuearray['enabled'])) {
             return $this->_prepareValue(0, $assoc);
         }
-        return $this->_prepareValue($valuearray['number'] * $valuearray['timeunit'], $assoc);
+        return $this->_prepareValue(
+                (int) round($valuearray['number'] * $valuearray['timeunit']), $assoc);
     }
 }

lib/form/tests/duration_test.php

@@ -145,6 +145,8 @@ class core_form_duration_testcase extends basic_testcase {
     public function export_value_cases(): array {
         return [
             [10, '10', 1],
+            [9, '9.3', 1],
+            [10, '9.5', 1],
             [180, '3', MINSECS],
             [90, '1.5', MINSECS],
             [7200, '2', HOURSECS],