private static final class TestCallable implements AsyncCallable<@Nullable Void> {

    private final ListenableFuture<@Nullable Void> future;
    private boolean called = false;

    private TestCallable(ListenableFuture<@Nullable Void> future) {
      this.future = future;
    }

    @Override
    public ListenableFuture<@Nullable Void> call() throws Exception {
      called = true;
      return future;
    }
  }

   * #setFuture(ListenableFuture)}.
   */
  private static final class AsyncTransformFuture<
          I extends @Nullable Object, O extends @Nullable Object>
      extends AbstractTransformFuture<
          I, O, AsyncFunction<? super I, ? extends O>, ListenableFuture<? extends O>> {
    AsyncTransformFuture(

  @SafeVarargs
  public static <V extends @Nullable Object> ListenableFuture<List<V>> allAsList(
      ListenableFuture<? extends V>... futures) {
    ListenableFuture<List<@Nullable V>> nullable =
        new ListFuture<V>(ImmutableList.copyOf(futures), true);
    // allAsList ensures that it fills the output list with V instances.
    @SuppressWarnings("nullness")
    ListenableFuture<List<V>> nonNull = nullable;
    return nonNull;
  }

  private static final class TestCallable implements AsyncCallable<@Nullable Void> {

    private final ListenableFuture<@Nullable Void> future;
    private boolean called = false;

    private TestCallable(ListenableFuture<@Nullable Void> future) {
      this.future = future;
    }

    @Override
    public ListenableFuture<@Nullable Void> call() throws Exception {
      called = true;
      return future;
    }
  }

  @SafeVarargs
  public static <V extends @Nullable Object> ListenableFuture<List<V>> allAsList(
      ListenableFuture<? extends V>... futures) {
    ListenableFuture<List<@Nullable V>> nullable =
        new ListFuture<V>(ImmutableList.copyOf(futures), true);
    // allAsList ensures that it fills the output list with V instances.
    @SuppressWarnings("nullness")
    ListenableFuture<List<V>> nonNull = nullable;
    return nonNull;
  }

          V, X, AsyncFunction<? super X, ? extends V>, ListenableFuture<? extends V>> {
    AsyncCatchingFuture(
        ListenableFuture<? extends V> input,
        Class<X> exceptionType,
        AsyncFunction<? super X, ? extends V> fallback) {
      super(input, exceptionType, fallback);
    }

    @Override
    ListenableFuture<? extends V> doFallback(

  }

  /**
   * Override to return a chaining listenableFuture that returns the result of getSuccessfulResult()
   * when inputFuture returns VALID_INPUT_DATA, and sets the exception to EXCEPTION in all other
   * cases.
   */
  protected abstract ListenableFuture<T> buildChainingFuture(ListenableFuture<Integer> inputFuture);

  /**

   *   <li>Return a {@code ClosingFuture}. To turn a {@link ListenableFuture} into a {@code
   *       ClosingFuture} call {@link #from(ListenableFuture)}.
   *   <li>In case this step doesn't create new closeables, you can adapt an API that returns a
   *       {@link ListenableFuture} to return a {@code ClosingFuture} by wrapping it with a call to
   *       {@link #withoutCloser(AsyncFunction)}

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.Maps;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Utility {@link CacheLoader} implementations intended for use in testing.

  private CountDownLatch funcIsWaitingLatch;
  // Signals the function so it will complete
  private CountDownLatch funcCompletionLatch;

  @Override
  protected ListenableFuture<String> buildChainingFuture(ListenableFuture<Integer> inputFuture) {
    outputFuture = SettableFuture.create();
    funcIsWaitingLatch = new CountDownLatch(1);
    funcCompletionLatch = new CountDownLatch(1);