@Override
    public Iterable<K> loadAllKeys() {
        long startNanos = Timer.nanos();
        try {
            return delegate.loadAllKeys();
        } finally {
            loadAllKeysProbe.recordValue(Timer.nanosElapsed(startNanos));
        }
    }
@Test
    public void loadAllKeys() {
        Collection<String> keys = asList("key1", "key2");

        when(delegate.loadAllKeys()).thenReturn(keys);

        Iterable<String> result = cacheLoader.loadAllKeys();

        assertSame(keys, result);
        assertProbeCalledOnce("loadAllKeys");
    }