Add spec for feature spec when on/off

Only show reviewers dropdown when feature flag is on.
Otherwise, there is no reviewers dropdown.

app/helpers/form_helper.rb

@@ -66,7 +66,8 @@ module FormHelper
         first_user: current_user&.username,
         null_user: true,
         current_user: true,
-        project_id: (@target_project || @project)&.id, field_name: "#{issuable_type}[reviewer_ids][]",
+        project_id: (@target_project || @project)&.id,
+        field_name: "#{issuable_type}[reviewer_ids][]",
         default_label: 'Unassigned',
         'dropdown-header': 'Reviewer(s)',
         multi_select: true,

app/views/shared/issuable/form/_metadata_issuable_reviewer.html.haml

@@ -4,7 +4,7 @@
     - issuable.reviewers.each do |reviewer|
       = hidden_field_tag "#{issuable.to_ability_name}[reviewer_ids][]", reviewer.id, id: nil, data: { meta: reviewer.name, avatar_url: reviewer.avatar_url, name: reviewer.name, username: reviewer.username }
 
-    - if issuable.reviewers.length === 0
+    - if issuable.reviewers.empty?
       = hidden_field_tag "#{issuable.to_ability_name}[reviewer_ids][]", 0, id: nil, data: { meta: '' }
 
     = dropdown_tag(users_dropdown_label(issuable.reviewers), options: reviewers_dropdown_options(issuable.to_ability_name))

spec/features/merge_request/user_edits_mr_spec.rb

@@ -7,7 +7,6 @@ RSpec.describe 'Merge request > User edits MR' do
 
   before do
     stub_licensed_features(multiple_merge_request_assignees: false)
-    stub_feature_flags(merge_request_reviewers: true)
   end
 
   context 'non-fork merge request' do
@@ -21,4 +20,32 @@ RSpec.describe 'Merge request > User edits MR' do
     include_context 'merge request edit context'
     it_behaves_like 'an editable merge request'
   end
+
+  context 'when merge_request_reviewers is turned on' do
+    before do
+      stub_feature_flags(merge_request_reviewers: true)
+    end
+
+    context 'non-fork merge request' do
+      include_context 'merge request edit context'
+      it_behaves_like 'an editable merge request with reviewers'
+    end
+
+    context 'for a forked project' do
+      let(:source_project) { fork_project(target_project, nil, repository: true) }
+
+      include_context 'merge request edit context'
+      it_behaves_like 'an editable merge request with reviewers'
+    end
+  end
+
+  context 'when merge_request_reviewers is turned off' do
+    before do
+      stub_feature_flags(merge_request_reviewers: false)
+    end
+
+    it 'does not render reviewers dropdown' do
+      expect(page).not_to have_selector('.js-reviewer-search')
+    end
+  end
 end

spec/support/shared_examples/features/editable_merge_request_shared_examples.rb

@@ -11,15 +11,6 @@ RSpec.shared_examples 'an editable merge request' do
       expect(page).to have_content user.name
     end
 
-    find('.js-reviewer-search').click
-    page.within '.dropdown-menu-user' do
-      click_link user.name
-    end
-    expect(find('input[name="merge_request[reviewer_ids][]"]', visible: false).value).to match(user.id.to_s)
-    page.within '.js-reviewer-search' do
-      expect(page).to have_content user.name
-    end
-
     click_button 'Milestone'
     page.within '.issue-milestone' do
       click_link milestone.title
@@ -133,3 +124,16 @@ end
 def get_textarea_height
   page.evaluate_script('document.getElementById("merge_request_description").offsetHeight')
 end
+
+RSpec.shared_examples 'an editable merge request with reviewers' do
+  it 'updates merge request', :js do
+    find('.js-reviewer-search').click
+    page.within '.dropdown-menu-user' do
+      click_link user.name
+    end
+    expect(find('input[name="merge_request[reviewer_ids][]"]', visible: false).value).to match(user.id.to_s)
+    page.within '.js-reviewer-search' do
+      expect(page).to have_content user.name
+    end
+  end
+end