build: debug rules_sass error

Author: crisbeto

src/material-experimental/mdc-menu/menu.spec.ts

@@ -234,6 +234,7 @@ describe('MDC-based MatMenu', () => {
 
     expect(document.activeElement).toBe(triggerEl);
     tick(500);
+    expect(Date.now()).toBeGreaterThan(0);
   }));
 
   it('should be able to set a custom class on the backdrop', fakeAsync(() => {