* {@link #unmodifiableKeySet()}. By design, the cache is cleared when this structure is mutated. If
 * this structure is never mutated, it provides a thread-safe view of the backing map.
 *
 * <p>The {@link MapIteratorCache} assumes ownership of the backing map, and cannot guarantee
 * correctness in the face of external mutations to the backing map. As such, it is <b>strongly</b>

/** Tests for {@link MapIteratorCache} and {@link MapRetrievalCache}. */
@AndroidIncompatible
// TODO(cpovirk): Figure out Android JUnit 4 support. Does it work with Gingerbread? @RunWith?
@RunWith(Parameterized.class)
@NullUnmarked
public final class MapCacheTest {
  private final MapIteratorCache<String, String> mapCache;

  public MapCacheTest(MapIteratorCache<String, String> mapCache) {

import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * A {@link MapIteratorCache} that adds additional caching. In addition to the caching provided by
 * {@link MapIteratorCache}, this structure caches values for the two most recently retrieved keys.
 *
 * @author James Sexton
 */
final class MapRetrievalCache<K, V> extends MapIteratorCache<K, V> {
  // See the note about volatile in the superclass.

     * The real purpose of this test is to produce a TSAN failure if MapIteratorCache is unsafe for
     * reads from multiple threads -- unsafe, in fact, even in the absence of a concurrent write.
     * The specific problem we had was unsafe reads of lastEntryReturnedBySomeIterator. (To fix the
     * problem, we've since marked that field as volatile.)
     *
     * When MapIteratorCache is used from Immutable* classes, the TSAN failure doesn't indicate a