@Override
    public String toString() {
        return "EntryTaskScheduler{"
                + "numberOfEntries="
                + size()
                + ", numberOfKeys="
                + keys.size()
                + ", numberOfGroups="
                + groups.size()
                + '}';
    }
@Test
    public void test_toString() {
        scheduler = new SecondsBasedEntryTaskScheduler<>(taskScheduler, entryProcessor, FOR_EACH);

        assertNotNull(scheduler.toString());
    }