Use correct identifier to find input.

renderer.php

@@ -1664,7 +1664,7 @@ class mod_attendance_renderer extends plugin_renderer_base {
             $cells[] = $this->construct_preferences_actions_icons($st, $prefdata);
 
             $table->data[$i] = new html_table_row($cells);
-            $table->data[$i]->style = "statusrow".$i;
+            $table->data[$i]->id = "statusrow".$i;
             $i++;
         }
 

tests/behat/attendance_mod.feature

@@ -59,7 +59,7 @@ Feature: Teachers and Students can record session attendance
     And I am on "Course 1" course homepage
     And I follow "Attendance"
     And I follow "Status set"
-    And I set the field with xpath "//tr[@class='statusrow2']//td[@class='c4']/input" to "0"
+    And I set the field with xpath "//tr[@id='statusrow2']//td[@class='c4']/input" to "0"
     And I press "Update"
     And I log out
     And I log in as "student1"