@Test @SuppressWarnings("unchecked") public void scheduleWithFixedDelay() { when( (ScheduledFuture<Object>) delegate.scheduleWithFixedDelay( wrappedRunnable, 1, 2, TimeUnit.SECONDS)).thenReturn( expectedResult); ScheduledFuture<?> result = executor.scheduleWithFixedDelay(runnable, 1, 2, TimeUnit.SECONDS); assertThat(result).isEqualTo(expectedResult); verify(delegate).scheduleWithFixedDelay(wrappedRunnable, 1, 2, TimeUnit.SECONDS); }