long joinPosition()
    {
        long position = consumerPosition;

        for (final ReadablePosition subscriberPosition : subscriberPositions)
        {
            position = Math.min(subscriberPosition.getVolatile(), position);
        }

        return position;
    }
@Test
    void shouldHaveJoiningPositionZeroWhenNoSubscriptions()
    {
        assertThat(ipcPublication.joinPosition(), is(0L));
    }