@Test
    public void compositeExceptionIssue() {
        Single
            .just(new Throwable("ROOT ERROR"))
            .flatMapCompletable(rootError -> Observable
                .range(1, 10)
                .flatMapCompletable(testNumber -> Completable
                    .mergeArrayDelayError(
                        Completable.error(new RuntimeException("Test#" + testNumber + "A", rootError)),
                        Completable.error(new RuntimeException("Test#" + testNumber + "B", rootError))
                    )
                    .doOnError(Throwable::getCause)
                    .onErrorComplete()
                )
                .doOnComplete(() -> {
                    rootError.printStackTrace();
                })
            )
            .blockingAwait();
    }