if (result == CancellationException.class) {
        assertTrue(future.isCancelled());
        assertTrue(cancellationSuccess.get());
        // cancellation can interleave in 3 ways
        // 1. prior to setFuture
        // 2. after setFuture before set() on the future assigned
        // 3. after setFuture and set() are called but before the listener completes.