// Since holder.value is 2, applying 4 should yield 6.
    assertEquals(6, adder.apply(4).intValue());

    ListenableFuture<Integer> immediateFuture = immediateFuture(4);
    Future<Integer> transformedFuture = transform(immediateFuture, adder, directExecutor());

    // The composed future also yields 6.
    assertEquals(6, getDone(transformedFuture).intValue());

    // Repeated calls yield the same value even though the function's behavior

    // Since holder.value is 2, applying 4 should yield 6.
    assertEquals(6, adder.apply(4).intValue());

    ListenableFuture<Integer> immediateFuture = immediateFuture(4);
    Future<Integer> transformedFuture = transform(immediateFuture, adder, directExecutor());

    // The composed future also yields 6.
    assertEquals(6, getDone(transformedFuture).intValue());

    // Repeated calls yield the same value even though the function's behavior