Added a test for new action

spec/frontend/vue_shared/components/sidebar/labels_select_vue/store/actions_spec.js

@@ -264,4 +264,17 @@ describe('LabelsSelect Actions', () => {
       );
     });
   });
+
+  describe('updateLabelsSetState', () => {
+    it('updates labels `set` state to match `selectedLabels`', (done) => {
+      testAction(
+        actions.updateLabelsSetState,
+        {},
+        state,
+        [{ type: types.UPDATE_LABELS_SET_STATE }],
+        [],
+        done,
+      );
+    });
+  });
 });