@Test
public void doesNotReloadCacheWithinTimeLimit()
        throws Exception
{

    // fake clock returns current time, then the same thing again,
    // then 4 seconds later, then 8 seconds later.
    Clock fakeClock = mock(Clock.class);
    Instant now = Instant.now();
    when(fakeClock.millis()).thenCallRealMethod();
    when(fakeClock.instant()).thenReturn(
            now, // get("0") - first map loading
            now, // cache asks when the latest loading happened
            now.plus(Duration.ofSeconds(4)), // get("1") - no reloading
            // get("0") - should not even ask about the time as entry was found
            now.plus(Duration.ofSeconds(4)), // get("1") - no reloading
            now.plus(Duration.ofSeconds(8))); // get("1") - reload
    @SuppressWarnings("unchecked")
    Supplier<ImmutableMap> fakeSupplier = mock(Supplier.class);
    when(fakeSupplier.get()).thenReturn(
            ImmutableMap.of("0", 0),
            ImmutableMap.of("1", 1));
    // the map will always contain a single entry with the number of reloads as in
    // ("reloads" -> reloads)
    AtomicInteger reloads = new AtomicInteger(0);
    TimeBasedCache<String, Integer> cache = new TimeBasedCache<>(Duration.ofSeconds(5),
            () -> ImmutableMap.copyOf(ImmutableMap.of(Integer.toString(reloads.get()),
                    reloads.getAndIncrement())),
            ImmutableMap.of(), fakeClock);
    // should have only ("0" -> 0) in the map in the beginning
    assertNotNull(cache.get("0"));
    assertNull(cache.get("1"));
    // second time we try, the map should not reload
    assertNotNull(cache.get("0"));
    assertNull(cache.get("1"));
    // when the first reload happens, the cache contains ("1" -> 1)
    assertNotNull(cache.get("1"));
    assertNull(cache.get("0"));
}