Add test coverage for bug fix

spec/frontend/diffs/components/diff_row_utils_spec.js

@@ -143,10 +143,21 @@ describe('addCommentTooltip', () => {
     'Commenting on symbolic links that replace or are replaced by files is currently not supported.';
   const brokenRealTooltip =
     'Commenting on files that replace or are replaced by symbolic links is currently not supported.';
+  const commentTooltip = 'Add a comment to this line';
+  const dragTooltip = 'Add a comment to this line or drag for multiple lines';
+
   it('should return default tooltip', () => {
     expect(utils.addCommentTooltip()).toBeUndefined();
   });
 
+  it('should return comment tooltip', () => {
+    expect(utils.addCommentTooltip({})).toEqual(commentTooltip);
+  });
+
+  it('should return drag comment tooltip when dragging is enabled', () => {
+    expect(utils.addCommentTooltip({}, true)).toEqual(dragTooltip);
+  });
+
   it('should return broken symlink tooltip', () => {
     expect(utils.addCommentTooltip({ commentsDisabled: { wasSymbolic: true } })).toEqual(
       brokenSymLinkTooltip,