Button tooltip, delete unused sort attr and use qa link

app/assets/stylesheets/pages/issues.scss

@@ -308,6 +308,16 @@ ul.related-merge-requests > li {
   display: block;
 }
 
+.issue-sort-dropdown {
+  .btn-group {
+    width: 100%;
+  }
+
+  .reverse-sort-btn {
+    color: $gl-text-color-secondary;
+  }
+}
+
 @include media-breakpoint-up(sm) {
   .emoji-block .row {
     display: flex;

app/helpers/sorting_helper.rb

@@ -162,7 +162,7 @@ module SortingHelper
   end
 
   def issuable_sort_direction_button(sort_value)
-    link_class = 'btn btn-default'
+    link_class = 'btn btn-default has-tooltip reverse-sort-btn qa-reverse-sort'
     reverse_sort = issuable_reverse_sort_order_hash[sort_value]
 
     if reverse_sort
@@ -172,7 +172,7 @@ module SortingHelper
       link_class += ' disabled'
     end
 
-    link_to(reverse_url, type: 'button', class: link_class) do
+    link_to(reverse_url, type: 'button', class: link_class, title: 'Sort direction') do
       icon_suffix =
         case sort_value
         when sort_value_milestone, sort_value_due_date, /_asc\z/

app/models/concerns/issuable.rb

@@ -146,7 +146,7 @@ module Issuable
       sorted =
         case method.to_s
         when 'downvotes_desc'                       then order_downvotes_desc
-        when 'label_priority', 'label_priority_asc' then order_labels_priority(excluded_labels: excluded_labels)
+        when 'label_priority'                       then order_labels_priority(excluded_labels: excluded_labels)
         when 'label_priority_desc'                  then order_labels_priority('DESC', excluded_labels: excluded_labels)
         when 'milestone', 'milestone_due_asc'       then order_milestone_due_asc
         when 'milestone_due_desc'                   then order_milestone_due_desc

app/views/shared/issuable/_sort_dropdown.html.haml

@@ -2,7 +2,7 @@
 - sort_title = issuable_sort_option_title(sort_value)
 - viewing_issues = controller.controller_name == 'issues' || controller.action_name == 'issues'
 
-.dropdown.inline.prepend-left-10
+.dropdown.inline.prepend-left-10.issue-sort-dropdown
   .btn-group{ role: 'group' }
     .btn-group{ role: 'group' }
       %button.dropdown-toggle{ type: 'button', data: { toggle: 'dropdown', display: 'static' }, class: 'btn btn-default' }

spec/features/issuables/sorting_list_spec.rb

@@ -101,7 +101,7 @@ describe 'Sort Issuable List' do
           expect(first_merge_request).to include(last_updated_issuable.title)
           expect(last_merge_request).to include(first_updated_issuable.title)
 
-          find('.issues-other-filters .filter-dropdown-container a[type=button]').click
+          find('.issues-other-filters .filter-dropdown-container .qa-reverse-sort').click
 
           expect(first_merge_request).to include(first_updated_issuable.title)
           expect(last_merge_request).to include(last_updated_issuable.title)
@@ -204,7 +204,7 @@ describe 'Sort Issuable List' do
         expect(first_issue).to include(last_updated_issuable.title)
         expect(last_issue).to include(first_updated_issuable.title)
 
-        find('.issues-other-filters .filter-dropdown-container a[type=button]').click
+        find('.issues-other-filters .filter-dropdown-container .qa-reverse-sort').click
 
         expect(first_issue).to include(first_updated_issuable.title)
         expect(last_issue).to include(last_updated_issuable.title)

spec/helpers/sorting_helper_spec.rb

@@ -21,7 +21,7 @@ describe SortingHelper do
 
   describe '#issuable_sort_direction_button' do
     before do
-      allow(self).to receive(:request).and_return(double(path: 'http://test.com'))
+      allow(self).to receive(:request).and_return(double(path: 'http://test.com', query_parameters: {}))
     end
 
     it 'returns icon with sort-highest when sort is created_date' do