Add spec for root diff discussion note

spec/javascripts/notes_spec.js

@@ -362,13 +362,33 @@ import '~/notes';
           $form.closest.and.returnValues(row, $form);
           $form.find.and.returnValues(discussionContainer);
           body.attr.and.returnValue('');
-
-          Notes.prototype.renderDiscussionNote.call(notes, note, $form);
         });
 
         it('should call Notes.animateAppendNote', () => {
+          Notes.prototype.renderDiscussionNote.call(notes, note, $form);
+
           expect(Notes.animateAppendNote).toHaveBeenCalledWith(note.discussion_html, $('.main-notes-list'));
         });
+
+        it('should append to row selected with line_code', () => {
+          $form.length = 0;
+          note.discussion_line_code = 'line_code';
+          note.diff_discussion_html = '<tr></tr>';
+
+          const line = document.createElement('div');
+          line.id = note.discussion_line_code;
+          document.body.appendChild(line);
+
+          $form.closest.and.returnValues($form);
+          spyOn(document, 'getElementById').and.callThrough();
+          spyOn($.fn, 'after').and.callThrough();
+
+          Notes.prototype.renderDiscussionNote.call(notes, note, $form);
+
+          expect(document.getElementById).toHaveBeenCalledWith(note.discussion_line_code);
+          expect($.fn.after).toHaveBeenCalled();
+          expect(line.nextSibling.outerHTML).toEqual(note.diff_discussion_html);
+        });
       });
 
       describe('Discussion sub note', () => {