@ParameterizedTest
    @ArgumentsSource(AbortCauseArgumentProvider.class)
    void testAbortWithoutSubscriber(@Nullable Throwable cause) {
        @SuppressWarnings("unchecked")
        final Publisher<Integer> delegate = mock(Publisher.class);
        final PublisherBasedStreamMessage<Integer> p = new PublisherBasedStreamMessage<>(delegate);
        if (cause == null) {
            p.abort();
        } else {
            p.abort(cause);
        }

        // Publisher should not be involved at all because we are aborting without subscribing.
        verify(delegate, only()).subscribe(any(AbortableSubscriber.class));
    }
Tests if {@link PublisherBasedStreamMessage#abort()} prohibits further subscription.
core/src/test/java/com/linecorp/armeria/common/stream/PublisherBasedStreamMessageTest.java