/**
 * A simple in-memory cache, used by the testing fixtures.
 */
public class TestInMemoryIndexedCache<K, V> implements IndexedCache<K, V> {
    private final Map<Object, byte[]> entries = new ConcurrentHashMap<>();
    private final ProducerGuard<K> producerGuard = ProducerGuard.serial();
    private final Serializer<V> valueSerializer;

    public TestInMemoryIndexedCache(Serializer<V> valueSerializer) {
        this.valueSerializer = valueSerializer;

            assertNotClosed();
            IndexedCache<?, ?> indexedCache = caches.get(Pair.of(cacheDir, name));
            if (indexedCache == null) {
                indexedCache = new TestInMemoryIndexedCache<K, V>(valueSerializer);
                caches.put(Pair.of(cacheDir, name), indexedCache);
            }
            return Cast.uncheckedCast(indexedCache);
        }

        @Override