MDL-66378 gradereport_singleview: Add missing label for dropdown

grade/report/singleview/classes/local/ui/dropdown_attribute.php

@@ -93,7 +93,8 @@ class dropdown_attribute extends element {
                     'value' => $option,
                     'selected' => $selected == $option
                 ];
-            }, array_keys($options))
+            }, array_keys($options)),
+            'label' => get_string('gradefor', 'gradereport_singleview', $this->label),
         );
 
         return $OUTPUT->render_from_template('gradereport_singleview/dropdown_attribute', $context);

grade/report/singleview/templates/dropdown_attribute.mustache

@@ -28,6 +28,7 @@
         "selected": "true"
     }
 }}
+<label for="{{name}}" class="accesshide">{{label}}</label>
 <select id="{{name}}" name="{{name}}" class="custom-select" tabindex="1" {{#disabled}}disabled{{/disabled}}>
     {{#options}}
         <option value="{{value}}" {{#selected}}selected{{/selected}}>{{name}}</option>

grade/report/singleview/tests/behat/singleview.feature

@@ -87,7 +87,7 @@ Feature: We can use Single view
     And the field "Grade for james (Student) 1" matches value "12.05"
     And the field "Exclude for holly (Student) 2" matches value "1"
     And I select "new grade item 1" from the "Select grade item..." singleselect
-    And I click on "Very good" "option"
+    And I set the field "Grade for james (Student) 1" to "Very good"
     And I press "Save"
     Then I should see "Grades were set for 1 items"
     And I press "Continue"